blocks|key|1754112|text|下载文件的方法有很多。下面我将发布最常见的方法，这取决于您决定哪种方法更适合您的应用程序。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1754113|使用=============================================================并在对话框AsyncTask中显示下载进度|ordered-list-item|offset|length|style|CODE|1754114|此方法将允许您执行一些后台进程并同时更新UI+(在本例中，我们将更新进度条)。|1754115|进口：|1754116|import+android.os.PowerManager;
import+java.io.InputStream;
import+java.io.OutputStream;
import+java.io.FileOutputStream;
import+java.net.HttpURLConnection;|code-block|syntax|javascript|1754117|这是一个示例代码：|1754118|//+declare+the+dialog+as+a+member+field+of+your+activity
ProgressDialog+mProgressDialog;

//+instantiate+it+within+the+onCreate+method
mProgressDialog+=+new+ProgressDialog(YourActivity.this);
mProgressDialog.setMessage("A+message");
mProgressDialog.setIndeterminate(true);
mProgressDialog.setProgressStyle(ProgressDialog.STYLE_HORIZONTAL);
mProgressDialog.setCancelable(true);

//+execute+this+when+the+downloader+must+be+fired
final+DownloadTask+downloadTask+=+new+DownloadTask(YourActivity.this);
downloadTask.execute("the+url+to+the+file+you+want+to+download");

mProgressDialog.setOnCancelListener(new+DialogInterface.OnCancelListener()+{

++++@Override
++++public+void+onCancel(DialogInterface+dialog)+{
++++++++downloadTask.cancel(true);+//cancel+the+task
++++}
});|1754119|AsyncTask将如下所示：|1754120|//+usually,+subclasses+of+AsyncTask+are+declared+inside+the+activity+class.
//+that+way,+you+can+easily+modify+the+UI+thread+from+here
private+class+DownloadTask+extends+AsyncTask<String,+Integer,+String>+{

++++private+Context+context;
++++private+PowerManager.WakeLock+mWakeLock;

++++public+DownloadTask(Context+context)+{
++++++++this.context+=+context;
++++}

++++@Override
++++protected+String+doInBackground(String...+sUrl)+{
++++++++InputStream+input+=+null;
++++++++OutputStream+output+=+null;
++++++++HttpURLConnection+connection+=+null;
++++++++try+{
++++++++++++URL+url+=+new+URL(sUrl[0]);
++++++++++++connection+=+(HttpURLConnection)+url.openConnection();
++++++++++++connection.connect();

++++++++++++//+expect+HTTP+200+OK,+so+we+don't+mistakenly+save+error+report
++++++++++++//+instead+of+the+file
++++++++++++if+(connection.getResponseCode()+!=+HttpURLConnection.HTTP_OK)+{
++++++++++++++++return+"Server+returned+HTTP+"+%2B+connection.getResponseCode()
++++++++++++++++++++++++%2B+"+"+%2B+connection.getResponseMessage();
++++++++++++}

++++++++++++//+this+will+be+useful+to+display+download+percentage
++++++++++++//+might+be+-1:+server+did+not+report+the+length
++++++++++++int+fileLength+=+connection.getContentLength();

++++++++++++//+download+the+file
++++++++++++input+=+connection.getInputStream();
++++++++++++output+=+new+FileOutputStream("/sdcard/file_name.extension");

++++++++++++byte+data[]+=+new+byte[4096];
++++++++++++long+total+=+0;
++++++++++++int+count;
++++++++++++while+((count+=+input.read(data))+!=+-1)+{
++++++++++++++++//+allow+canceling+with+back+button
++++++++++++++++if+(isCancelled())+{
++++++++++++++++++++input.close();
++++++++++++++++++++return+null;
++++++++++++++++}
++++++++++++++++total+%2B=+count;
++++++++++++++++//+publishing+the+progress....
++++++++++++++++if+(fileLength+>+0)+//+only+if+total+length+is+known
++++++++++++++++++++publishProgress((int)+(total+*+100+/+fileLength));
++++++++++++++++output.write(data,+0,+count);
++++++++++++}
++++++++}+catch+(Exception+e)+{
++++++++++++return+e.toString();
++++++++}+finally+{
++++++++++++try+{
++++++++++++++++if+(output+!=+null)
++++++++++++++++++++output.close();
++++++++++++++++if+(input+!=+null)
++++++++++++++++++++input.close();
++++++++++++}+catch+(IOException+ignored)+{
++++++++++++}

++++++++++++if+(connection+!=+null)
++++++++++++++++connection.disconnect();
++++++++}
++++++++return+null;
++++}|1754121|上面的方法(doInBackground)总是在后台线程上运行。您不应该在那里执行任何UI任务。另一方面，onProgressUpdate和onPreExecute运行在UI线程上，因此您可以更改进度条：|1754122|++++@Override
++++protected+void+onPreExecute()+{
++++++++super.onPreExecute();
++++++++//+take+CPU+lock+to+prevent+CPU+from+going+off+if+the+user+
++++++++//+presses+the+power+button+during+download
++++++++PowerManager+pm+=+(PowerManager)+context.getSystemService(Context.POWER_SERVICE);
++++++++mWakeLock+=+pm.newWakeLock(PowerManager.PARTIAL_WAKE_LOCK,
+++++++++++++getClass().getName());
++++++++mWakeLock.acquire();
++++++++mProgressDialog.show();
++++}
++++
++++@Override
++++protected+void+onProgressUpdate(Integer...+progress)+{
++++++++super.onProgressUpdate(progress);
++++++++//+if+we+get+here,+length+is+known,+now+set+indeterminate+to+false
++++++++mProgressDialog.setIndeterminate(false);
++++++++mProgressDialog.setMax(100);
++++++++mProgressDialog.setProgress(progress[0]);
++++}

++++@Override
++++protected+void+onPostExecute(String+result)+{
++++++++mWakeLock.release();
++++++++mProgressDialog.dismiss();
++++++++if+(result+!=+null)
++++++++++++Toast.makeText(context,"Download+error:+"%2Bresult,+Toast.LENGTH_LONG).show();
++++++++else
++++++++++++Toast.makeText(context,"File+downloaded",+Toast.LENGTH_SHORT).show();
++++}
}|1754123|要运行该程序，需要WAKE_LOCK权限。|1754124|<uses-permission+android:name="android.permission.WAKE_LOCK"+/>|1754125|从服务========================下载|1754126|这里的大问题是:如何从服务中更新我的活动？在下一个示例中，我们将使用两个您可能不知道的类：ResultReceiver和IntentService。ResultReceiver允许我们从服务中更新线程；IntentService是Service的子类，它生成一个线程来从那里执行后台工作(您应该知道Service实际上运行在应用程序的同一个线程中；当您扩展Service时，您必须手动生成新线程来运行CPU阻塞操作)。|1754127|下载服务可以如下所示：|1754128|public+class+DownloadService+extends+IntentService+{
++++public+static+final+int+UPDATE_PROGRESS+=+8344;

++++public+DownloadService()+{
++++++++super("DownloadService");
++++}
++++@Override
++++protected+void+onHandleIntent(Intent+intent)+{

++++++++String+urlToDownload+=+intent.getStringExtra("url");
++++++++ResultReceiver+receiver+=+(ResultReceiver)+intent.getParcelableExtra("receiver");
++++++++try+{
++++++++++++
++++++++++++//create+url+and+connect
++++++++++++URL+url+=+new+URL(urlToDownload);
++++++++++++URLConnection+connection+=+url.openConnection();
++++++++++++connection.connect();

++++++++++++//+this+will+be+useful+so+that+you+can+show+a+typical+0-100%25+progress+bar
++++++++++++int+fileLength+=+connection.getContentLength();

++++++++++++//+download+the+file
++++++++++++InputStream+input+=+new+BufferedInputStream(connection.getInputStream());

++++++++++++String+path+=+"/sdcard/BarcodeScanner-debug.apk"+;
++++++++++++OutputStream+output+=+new+FileOutputStream(path);

++++++++++++byte+data[]+=+new+byte[1024];
++++++++++++long+total+=+0;
++++++++++++int+count;
++++++++++++while+((count+=+input.read(data))+!=+-1)+{
++++++++++++++++total+%2B=+count;

++++++++++++++++//+publishing+the+progress....
++++++++++++++++Bundle+resultData+=+new+Bundle();
++++++++++++++++resultData.putInt("progress"+,(int)+(total+*+100+/+fileLength));
++++++++++++++++receiver.send(UPDATE_PROGRESS,+resultData);
++++++++++++++++output.write(data,+0,+count);
++++++++++++}

++++++++++++//+close+streams+
++++++++++++output.flush();
++++++++++++output.close();
++++++++++++input.close();

++++++++}+catch+(IOException+e)+{
++++++++++++e.printStackTrace();
++++++++}

++++++++Bundle+resultData+=+new+Bundle();
++++++++resultData.putInt("progress"+,100);

++++++++receiver.send(UPDATE_PROGRESS,+resultData);
++++}
}|1754129|将服务添加到您的清单中：|1754130|<service+android:name=".DownloadService"/>|1754131|活动将会是这样的：|1754132|//+initialize+the+progress+dialog+like+in+the+first+example

//+this+is+how+you+fire+the+downloader
mProgressDialog.show();
Intent+intent+=+new+Intent(this,+DownloadService.class);
intent.putExtra("url",+"url+of+the+file+to+download");
intent.putExtra("receiver",+new+DownloadReceiver(new+Handler()));
startService(intent);|1754133|这里是ResultReceiver来玩的：|1754134|private+class+DownloadReceiver+extends+ResultReceiver{

++++public+DownloadReceiver(Handler+handler)+{
++++++++super(handler);
++++}

++++@Override
++++protected+void+onReceiveResult(int+resultCode,+Bundle+resultData)+{

++++++++super.onReceiveResult(resultCode,+resultData);

++++++++if+(resultCode+==+DownloadService.UPDATE_PROGRESS)+{

++++++++++++int+progress+=+resultData.getInt("progress");+//get+the+progress
++++++++++++dialog.setProgress(progress);

++++++++++++if+(progress+==+100)+{
++++++++++++++++dialog.dismiss();
++++++++++++}
++++++++}
++++}
}|1754135|2.1使用Groundy图书馆|1754136|土质是一个库，它基本上可以帮助您在后台服务中运行代码片段，它基于上面所示的ResultReceiver概念。这个库目前是不推荐的。这就是整个代码的样子：|BOLD|1754137|你显示对话框的活动..。|1754138|public+class+MainActivity+extends+Activity+{

++++private+ProgressDialog+mProgressDialog;

++++@Override
++++public+void+onCreate(Bundle+savedInstanceState)+{
++++++++super.onCreate(savedInstanceState);
++++++++setContentView(R.layout.main);

++++++++findViewById(R.id.btn_download).setOnClickListener(new+View.OnClickListener()+{
++++++++++++public+void+onClick(View+view)+{
++++++++++++++++String+url+=+((EditText)+findViewById(R.id.edit_url)).getText().toString().trim();
++++++++++++++++Bundle+extras+=+new+Bundler().add(DownloadTask.PARAM_URL,+url).build();
++++++++++++++++Groundy.create(DownloadExample.this,+DownloadTask.class)
++++++++++++++++++++++++.receiver(mReceiver)
++++++++++++++++++++++++.params(extras)
++++++++++++++++++++++++.queue();

++++++++++++++++mProgressDialog+=+new+ProgressDialog(MainActivity.this);
++++++++++++++++mProgressDialog.setProgressStyle(ProgressDialog.STYLE_HORIZONTAL);
++++++++++++++++mProgressDialog.setCancelable(false);
++++++++++++++++mProgressDialog.show();
++++++++++++}
++++++++});
++++}

++++private+ResultReceiver+mReceiver+=+new+ResultReceiver(new+Handler())+{
++++++++@Override
++++++++protected+void+onReceiveResult(int+resultCode,+Bundle+resultData)+{
++++++++++++super.onReceiveResult(resultCode,+resultData);
++++++++++++switch+(resultCode)+{
++++++++++++++++case+Groundy.STATUS_PROGRESS:
++++++++++++++++++++mProgressDialog.setProgress(resultData.getInt(Groundy.KEY_PROGRESS));
++++++++++++++++++++break;
++++++++++++++++case+Groundy.STATUS_FINISHED:
++++++++++++++++++++Toast.makeText(DownloadExample.this,+R.string.file_downloaded,+Toast.LENGTH_LONG);
++++++++++++++++++++mProgressDialog.dismiss();
++++++++++++++++++++break;
++++++++++++++++case+Groundy.STATUS_ERROR:
++++++++++++++++++++Toast.makeText(DownloadExample.this,+resultData.getString(Groundy.KEY_ERROR),+Toast.LENGTH_LONG).show();
++++++++++++++++++++mProgressDialog.dismiss();
++++++++++++++++++++break;
++++++++++++}
++++++++}
++++};
}|1754139|GroundyTask实现Groundy用于下载文件并显示进度：|1754140|public+class+DownloadTask+extends+GroundyTask+{++++
++++public+static+final+String+PARAM_URL+=+"com.groundy.sample.param.url";

++++@Override
++++protected+boolean+doInBackground()+{
++++++++try+{
++++++++++++String+url+=+getParameters().getString(PARAM_URL);
++++++++++++File+dest+=+new+File(getContext().getFilesDir(),+new+File(url).getName());
++++++++++++DownloadUtils.downloadFile(getContext(),+url,+dest,+DownloadUtils.getDownloadListenerForTask(this));
++++++++++++return+true;
++++++++}+catch+(Exception+pokemon)+{
++++++++++++return+false;
++++++++}
++++}
}|1754141|然后把这个添加到清单中：|1754142|<service+android:name="com.codeslap.groundy.GroundyService"/>|1754143|我想再简单不过了。只要拿上最新的jar+来自吉突布，你就可以出发了。请记住，Groundy的主要目的是在后台服务中调用外部REST+app，并轻松地将结果发布到UI中。|1754144|2.2使用https://github.com/koush/ion|1754145|使用=============================================================类(+DownloadManager类(GingerBread和更新版本))|1754146|GingerBread带来了一个新特性DownloadManager，它允许您轻松下载文件，并将处理线程、流等的艰苦工作委托给系统。|1754147|首先，让我们看看实用程序方法：|1754148|/**
+*+@param+context+used+to+check+the+device+version+and+DownloadManager+information
+*+@return+true+if+the+download+manager+is+available
+*/
public+static+boolean+isDownloadManagerAvailable(Context+context)+{

++++if+(Build.VERSION.SDK_INT+>=+Build.VERSION_CODES.GINGERBREAD)+{
++++++++return+true;
++++}
++++return+false;
}|1754149|方法的名字解释了这一切。一旦您确信DownloadManager是可用的，您就可以这样做：|1754150|String+url+=+"url+you+want+to+download";
DownloadManager.Request+request+=+new+DownloadManager.Request(Uri.parse(url));
request.setDescription("Some+descrition");
request.setTitle("Some+title");
//+in+order+for+this+if+to+run,+you+must+use+the+android+3.2+to+compile+your+app
if+(Build.VERSION.SDK_INT+>=+Build.VERSION_CODES.HONEYCOMB)+{
++++request.allowScanningByMediaScanner();
++++request.setNotificationVisibility(DownloadManager.Request.VISIBILITY_VISIBLE_NOTIFY_COMPLETED);
}
request.setDestinationInExternalPublicDir(Environment.DIRECTORY_DOWNLOADS,+"name-of-the-file.ext");

//+get+download+service+and+enqueue+file
DownloadManager+manager+=+(DownloadManager)+getSystemService(Context.DOWNLOAD_SERVICE);
manager.enqueue(request);|1754151|下载进度将显示在通知栏中。|1754152|最后的思想|1754153|第一和第二种方法只是冰山一角。如果你想让你的应用变得健壮，你必须记住很多事情。以下是一个简短的清单：|1754154|您必须检查用户是否有可用的internet连接。|unordered-list-item|1754155|确保您拥有正确的权限(INTERNET和WRITE_EXTERNAL_STORAGE)；如果要检查internet可用性，也要确保具有ACCESS_NETWORK_STATE。|1754156|如果要下载文件，请确保目录存在并具有写权限。|1754157|如果下载太大，如果以前的尝试失败，您可能希望实现一种恢复下载的方法。|1754158|如果您允许用户中断下载，用户将不胜感激。|1754159|除非您需要对下载过程进行详细控制，否则请考虑使用DownloadManager+(3)，因为它已经处理了上面列出的大多数项目。|1754160|但也要考虑到你的需求可能会改变。例如，DownloadManager+没有响应缓存。它将盲目下载同一大文件多次。在事实发生之后，没有什么容易的办法来解决这个问题。如果您从基本的HttpURLConnection+(1，2)开始，那么只需要添加一个HttpResponseCache。因此，初步努力学习基本的、标准的工具可以是一个很好的投资。|1754161|这个类在API级别26中被废弃。ProgressDialog是一个模式对话框，它阻止用户与应用程序交互。不要使用这个类，您应该使用像ProgressBar这样的进度指示器，它可以嵌入到应用程序的UI中。或者，您可以使用通知通知用户任务的进度。有关更多细节，链接|blockquote|1754162|entityMap|0|LINK|mutability|MUTABLE|url|http://github.com/casidiablo/groundy|1|https://github.com/casidiablo/groundy/downloads|2|https://github.com/koush/ion|3|https://stackoverflow.com/questions/35191718|4|https://developer.android.com/reference/android/app/ProgressDialog^0|0|1W|9|0|0|0|0|0|0|0|9|0|0|6|E|1H|G|1Y|C|0|0|0|0|0|19|E|1O|D|22|E|2T|D|37|7|45|7|4Y|7|0|0|0|0|0|0|0|3|E|0|0|0|11|E|1O|4|1W|2|0|2|0|0|0|0|0|B|D|7|0|0|0|0|12|7|K|5|1|0|5|S|2|0|1U|F|2B|B|0|J|F|0|0|0|H|F|0|0|0|0|0|0|B|8|K|M|1V|K|0|0|0|0|O|F|0|J|F|2G|H|3F|H|Z|6|3|0|3K|2|4|0^^$0|@$1|2|3|4|5|6|7|3S|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|3T|8|@$E|3U|F|3V|G|H]]|9|@]|A|$]]|$1|I|3|J|5|6|7|3W|8|@]|9|@]|A|$]]|$1|K|3|L|5|6|7|3X|8|@]|9|@]|A|$]]|$1|M|3|N|5|O|7|3Y|8|@]|9|@]|A|$P|Q]]|$1|R|3|S|5|6|7|3Z|8|@]|9|@]|A|$]]|$1|T|3|U|5|O|7|40|8|@]|9|@]|A|$P|Q]]|$1|V|3|W|5|6|7|41|8|@$E|42|F|43|G|H]]|9|@]|A|$]]|$1|X|3|Y|5|O|7|44|8|@]|9|@]|A|$P|Q]]|$1|Z|3|10|5|6|7|45|8|@$E|46|F|47|G|H]|$E|48|F|49|G|H]|$E|4A|F|4B|G|H]]|9|@]|A|$]]|$1|11|3|12|5|O|7|4C|8|@]|9|@]|A|$P|Q]]|$1|13|3|14|5|6|7|4D|8|@]|9|@]|A|$]]|$1|15|3|16|5|O|7|4E|8|@]|9|@]|A|$P|Q]]|$1|17|3|18|5|D|7|4F|8|@]|9|@]|A|$]]|$1|19|3|1A|5|6|7|4G|8|@$E|4H|F|4I|G|H]|$E|4J|F|4K|G|H]|$E|4L|F|4M|G|H]|$E|4N|F|4O|G|H]|$E|4P|F|4Q|G|H]|$E|4R|F|4S|G|H]|$E|4T|F|4U|G|H]]|9|@]|A|$]]|$1|1B|3|1C|5|6|7|4V|8|@]|9|@]|A|$]]|$1|1D|3|1E|5|O|7|4W|8|@]|9|@]|A|$P|Q]]|$1|1F|3|1G|5|6|7|4X|8|@]|9|@]|A|$]]|$1|1H|3|1I|5|O|7|4Y|8|@]|9|@]|A|$P|Q]]|$1|1J|3|1K|5|6|7|4Z|8|@]|9|@]|A|$]]|$1|1L|3|1M|5|O|7|50|8|@]|9|@]|A|$P|Q]]|$1|1N|3|1O|5|6|7|51|8|@$E|52|F|53|G|H]]|9|@]|A|$]]|$1|1P|3|1Q|5|O|7|54|8|@]|9|@]|A|$P|Q]]|$1|1R|3|1S|5|6|7|55|8|@]|9|@]|A|$]]|$1|1T|3|1U|5|6|7|56|8|@$E|57|F|58|G|H]|$E|59|F|5A|G|1V]|$E|5B|F|5C|G|1V]]|9|@$E|5D|F|5E|1|5F]]|A|$]]|$1|1W|3|1X|5|6|7|5G|8|@]|9|@]|A|$]]|$1|1Y|3|1Z|5|O|7|5H|8|@]|9|@]|A|$P|Q]]|$1|20|3|21|5|6|7|5I|8|@$E|5J|F|5K|G|H]|$E|5L|F|5M|G|1V]]|9|@]|A|$]]|$1|22|3|23|5|O|7|5N|8|@]|9|@]|A|$P|Q]]|$1|24|3|25|5|6|7|5O|8|@]|9|@]|A|$]]|$1|26|3|27|5|O|7|5P|8|@]|9|@]|A|$P|Q]]|$1|28|3|29|5|6|7|5Q|8|@$E|5R|F|5S|G|1V]]|9|@$E|5T|F|5U|1|5V]]|A|$]]|$1|2A|3|2B|5|6|7|5W|8|@]|9|@$E|5X|F|5Y|1|5Z]]|A|$]]|$1|2C|3|2D|5|D|7|60|8|@$E|61|F|62|G|H]|$E|63|F|64|G|H]]|9|@]|A|$]]|$1|2E|3|2F|5|6|7|65|8|@$E|66|F|67|G|H]]|9|@]|A|$]]|$1|2G|3|2H|5|6|7|68|8|@]|9|@]|A|$]]|$1|2I|3|2J|5|O|7|69|8|@]|9|@]|A|$P|Q]]|$1|2K|3|2L|5|6|7|6A|8|@$E|6B|F|6C|G|H]]|9|@]|A|$]]|$1|2M|3|2N|5|O|7|6D|8|@]|9|@]|A|$P|Q]]|$1|2O|3|2P|5|6|7|6E|8|@]|9|@]|A|$]]|$1|2Q|3|2R|5|6|7|6F|8|@]|9|@]|A|$]]|$1|2S|3|2T|5|6|7|6G|8|@]|9|@]|A|$]]|$1|2U|3|2V|5|2W|7|6H|8|@]|9|@]|A|$]]|$1|2X|3|2Y|5|2W|7|6I|8|@$E|6J|F|6K|G|H]|$E|6L|F|6M|G|H]|$E|6N|F|6O|G|H]]|9|@]|A|$]]|$1|2Z|3|30|5|2W|7|6P|8|@]|9|@]|A|$]]|$1|31|3|32|5|2W|7|6Q|8|@]|9|@]|A|$]]|$1|33|3|34|5|2W|7|6R|8|@]|9|@]|A|$]]|$1|35|3|36|5|6|7|6S|8|@$E|6T|F|6U|G|H]]|9|@]|A|$]]|$1|37|3|38|5|6|7|6V|8|@$E|6W|F|6X|G|H]|$E|6Y|F|6Z|G|H]|$E|70|F|71|G|H]]|9|@$E|72|F|73|1|74]]|A|$]]|$1|39|3|3A|5|3B|7|75|8|@]|9|@$E|76|F|77|1|78]]|A|$]]|$1|3C|3|-4|5|6|7|79|8|@]|9|@]|A|$]]]|3D|$3E|$5|3F|3G|3H|A|$3I|3J]]|3K|$5|3F|3G|3H|A|$3I|3L]]|3M|$5|3F|3G|3H|A|$3I|3N]]|3O|$5|3F|3G|3H|A|$3I|3P]]|3Q|$5|3F|3G|3H|A|$3I|3R]]]]

There are many ways to download files. Following I will post most common ways; it is up to you to decide which method is better for your app.
<ol>
<li>Use <code>AsyncTask</code> and show the download progress in a dialog
=============================================================</li>
</ol>
This method will allow you to execute some background processes and update the UI at the same time (in this case, we'll update a progress bar).
Imports:
<pre><code>import android.os.PowerManager;
import java.io.InputStream;
import java.io.OutputStream;
import java.io.FileOutputStream;
import java.net.HttpURLConnection;
</code></pre>
This is an example code:
<pre><code>// declare the dialog as a member field of your activity
ProgressDialog mProgressDialog;

// instantiate it within the onCreate method
mProgressDialog = new ProgressDialog(YourActivity.this);
mProgressDialog.setMessage(&quot;A message&quot;);
mProgressDialog.setIndeterminate(true);
mProgressDialog.setProgressStyle(ProgressDialog.STYLE_HORIZONTAL);
mProgressDialog.setCancelable(true);

// execute this when the downloader must be fired
final DownloadTask downloadTask = new DownloadTask(YourActivity.this);
downloadTask.execute(&quot;the url to the file you want to download&quot;);

mProgressDialog.setOnCancelListener(new DialogInterface.OnCancelListener() {

 @Override
 public void onCancel(DialogInterface dialog) {
 downloadTask.cancel(true); //cancel the task
 }
});
</code></pre>
The <code>AsyncTask</code> will look like this:
<pre><code>// usually, subclasses of AsyncTask are declared inside the activity class.
// that way, you can easily modify the UI thread from here
private class DownloadTask extends AsyncTask&lt;String, Integer, String&gt; {

 private Context context;
 private PowerManager.WakeLock mWakeLock;

 public DownloadTask(Context context) {
 this.context = context;
 }

 @Override
 protected String doInBackground(String... sUrl) {
 InputStream input = null;
 OutputStream output = null;
 HttpURLConnection connection = null;
 try {
 URL url = new URL(sUrl[0]);
 connection = (HttpURLConnection) url.openConnection();
 connection.connect();

 // expect HTTP 200 OK, so we don't mistakenly save error report
 // instead of the file
 if (connection.getResponseCode() != HttpURLConnection.HTTP_OK) {
 return &quot;Server returned HTTP &quot; + connection.getResponseCode()
 + &quot; &quot; + connection.getResponseMessage();
 }

 // this will be useful to display download percentage
 // might be -1: server did not report the length
 int fileLength = connection.getContentLength();

 // download the file
 input = connection.getInputStream();
 output = new FileOutputStream(&quot;/sdcard/file_name.extension&quot;);

 byte data[] = new byte[4096];
 long total = 0;
 int count;
 while ((count = input.read(data)) != -1) {
 // allow canceling with back button
 if (isCancelled()) {
 input.close();
 return null;
 }
 total += count;
 // publishing the progress....
 if (fileLength &gt; 0) // only if total length is known
 publishProgress((int) (total * 100 / fileLength));
 output.write(data, 0, count);
 }
 } catch (Exception e) {
 return e.toString();
 } finally {
 try {
 if (output != null)
 output.close();
 if (input != null)
 input.close();
 } catch (IOException ignored) {
 }

 if (connection != null)
 connection.disconnect();
 }
 return null;
 }
</code></pre>
The method above (<code>doInBackground</code>) runs always on a background thread. You shouldn't do any UI tasks there. On the other hand, the <code>onProgressUpdate</code> and <code>onPreExecute</code> run on the UI thread, so there you can change the progress bar:
<pre><code> @Override
 protected void onPreExecute() {
 super.onPreExecute();
 // take CPU lock to prevent CPU from going off if the user 
 // presses the power button during download
 PowerManager pm = (PowerManager) context.getSystemService(Context.POWER_SERVICE);
 mWakeLock = pm.newWakeLock(PowerManager.PARTIAL_WAKE_LOCK,
 getClass().getName());
 mWakeLock.acquire();
 mProgressDialog.show();
 }
 
 @Override
 protected void onProgressUpdate(Integer... progress) {
 super.onProgressUpdate(progress);
 // if we get here, length is known, now set indeterminate to false
 mProgressDialog.setIndeterminate(false);
 mProgressDialog.setMax(100);
 mProgressDialog.setProgress(progress[0]);
 }

 @Override
 protected void onPostExecute(String result) {
 mWakeLock.release();
 mProgressDialog.dismiss();
 if (result != null)
 Toast.makeText(context,&quot;Download error: &quot;+result, Toast.LENGTH_LONG).show();
 else
 Toast.makeText(context,&quot;File downloaded&quot;, Toast.LENGTH_SHORT).show();
 }
}
</code></pre>
For this to run, you need the WAKE_LOCK permission.
<pre><code>&lt;uses-permission android:name=&quot;android.permission.WAKE_LOCK&quot; /&gt;
</code></pre>
<ol start="2">
<li>Download from Service
========================</li>
</ol>
The big question here is: how do I update my activity from a service?. In the next example we are going to use two classes you may not be aware of: <code>ResultReceiver</code> and <code>IntentService</code>. <code>ResultReceiver</code> is the one that will allow us to update our thread from a service; <code>IntentService</code> is a subclass of <code>Service</code> which spawns a thread to do background work from there (you should know that a <code>Service</code> runs actually in the same thread of your app; when you extends <code>Service</code>, you must manually spawn new threads to run CPU blocking operations).
Download service can look like this:
<pre><code>public class DownloadService extends IntentService {
 public static final int UPDATE_PROGRESS = 8344;

 public DownloadService() {
 super(&quot;DownloadService&quot;);
 }
 @Override
 protected void onHandleIntent(Intent intent) {

 String urlToDownload = intent.getStringExtra(&quot;url&quot;);
 ResultReceiver receiver = (ResultReceiver) intent.getParcelableExtra(&quot;receiver&quot;);
 try {
 
 //create url and connect
 URL url = new URL(urlToDownload);
 URLConnection connection = url.openConnection();
 connection.connect();

 // this will be useful so that you can show a typical 0-100% progress bar
 int fileLength = connection.getContentLength();

 // download the file
 InputStream input = new BufferedInputStream(connection.getInputStream());

 String path = &quot;/sdcard/BarcodeScanner-debug.apk&quot; ;
 OutputStream output = new FileOutputStream(path);

 byte data[] = new byte[1024];
 long total = 0;
 int count;
 while ((count = input.read(data)) != -1) {
 total += count;

 // publishing the progress....
 Bundle resultData = new Bundle();
 resultData.putInt(&quot;progress&quot; ,(int) (total * 100 / fileLength));
 receiver.send(UPDATE_PROGRESS, resultData);
 output.write(data, 0, count);
 }

 // close streams 
 output.flush();
 output.close();
 input.close();

 } catch (IOException e) {
 e.printStackTrace();
 }

 Bundle resultData = new Bundle();
 resultData.putInt(&quot;progress&quot; ,100);

 receiver.send(UPDATE_PROGRESS, resultData);
 }
}
</code></pre>
Add the service to your manifest:
<pre><code>&lt;service android:name=&quot;.DownloadService&quot;/&gt;
</code></pre>
And the activity will look like this:
<pre><code>// initialize the progress dialog like in the first example

// this is how you fire the downloader
mProgressDialog.show();
Intent intent = new Intent(this, DownloadService.class);
intent.putExtra(&quot;url&quot;, &quot;url of the file to download&quot;);
intent.putExtra(&quot;receiver&quot;, new DownloadReceiver(new Handler()));
startService(intent);
</code></pre>
Here is were <code>ResultReceiver</code> comes to play:
<pre><code>private class DownloadReceiver extends ResultReceiver{

 public DownloadReceiver(Handler handler) {
 super(handler);
 }

 @Override
 protected void onReceiveResult(int resultCode, Bundle resultData) {

 super.onReceiveResult(resultCode, resultData);

 if (resultCode == DownloadService.UPDATE_PROGRESS) {

 int progress = resultData.getInt(&quot;progress&quot;); //get the progress
 dialog.setProgress(progress);

 if (progress == 100) {
 dialog.dismiss();
 }
 }
 }
}
</code></pre>
<h2>2.1 Use Groundy library</h2>
<a href="http://github.com/casidiablo/groundy" rel="noreferrer">Groundy</a> is a library that basically helps you run pieces of code in a background service, and it is based on the <code>ResultReceiver</code> concept shown above. This library is deprecated at the moment. This is how the whole code would look like:
The activity where you are showing the dialog...
<pre><code>public class MainActivity extends Activity {

 private ProgressDialog mProgressDialog;

 @Override
 public void onCreate(Bundle savedInstanceState) {
 super.onCreate(savedInstanceState);
 setContentView(R.layout.main);

 findViewById(R.id.btn_download).setOnClickListener(new View.OnClickListener() {
 public void onClick(View view) {
 String url = ((EditText) findViewById(R.id.edit_url)).getText().toString().trim();
 Bundle extras = new Bundler().add(DownloadTask.PARAM_URL, url).build();
 Groundy.create(DownloadExample.this, DownloadTask.class)
 .receiver(mReceiver)
 .params(extras)
 .queue();

 mProgressDialog = new ProgressDialog(MainActivity.this);
 mProgressDialog.setProgressStyle(ProgressDialog.STYLE_HORIZONTAL);
 mProgressDialog.setCancelable(false);
 mProgressDialog.show();
 }
 });
 }

 private ResultReceiver mReceiver = new ResultReceiver(new Handler()) {
 @Override
 protected void onReceiveResult(int resultCode, Bundle resultData) {
 super.onReceiveResult(resultCode, resultData);
 switch (resultCode) {
 case Groundy.STATUS_PROGRESS:
 mProgressDialog.setProgress(resultData.getInt(Groundy.KEY_PROGRESS));
 break;
 case Groundy.STATUS_FINISHED:
 Toast.makeText(DownloadExample.this, R.string.file_downloaded, Toast.LENGTH_LONG);
 mProgressDialog.dismiss();
 break;
 case Groundy.STATUS_ERROR:
 Toast.makeText(DownloadExample.this, resultData.getString(Groundy.KEY_ERROR), Toast.LENGTH_LONG).show();
 mProgressDialog.dismiss();
 break;
 }
 }
 };
}
</code></pre>
A <code>GroundyTask</code> implementation used by Groundy to download the file and show the progress:
<pre><code>public class DownloadTask extends GroundyTask { 
 public static final String PARAM_URL = &quot;com.groundy.sample.param.url&quot;;

 @Override
 protected boolean doInBackground() {
 try {
 String url = getParameters().getString(PARAM_URL);
 File dest = new File(getContext().getFilesDir(), new File(url).getName());
 DownloadUtils.downloadFile(getContext(), url, dest, DownloadUtils.getDownloadListenerForTask(this));
 return true;
 } catch (Exception pokemon) {
 return false;
 }
 }
}
</code></pre>
And just add this to the manifest:
<pre><code>&lt;service android:name=&quot;com.codeslap.groundy.GroundyService&quot;/&gt;
</code></pre>
It couldn't be easier I think. Just grab the latest jar <a href="https://github.com/casidiablo/groundy/downloads" rel="noreferrer">from Github</a> and you are ready to go. Keep in mind that Groundy's main purpose is to make calls to external REST apis in a background service and post results to the UI with easily. If you are doing something like that in your app, it could be really useful.
<h2>2.2 Use <a href="https://github.com/koush/ion" rel="noreferrer">https://github.com/koush/ion</a></h2>
<ol start="3">
<li>Use <code>DownloadManager</code> class (<code>GingerBread</code> and newer only)
=============================================================</li>
</ol>
GingerBread brought a new feature, <code>DownloadManager</code>, which allows you to download files easily and delegate the hard work of handling threads, streams, etc. to the system.
First, let's see a utility method:
<pre><code>/**
 * @param context used to check the device version and DownloadManager information
 * @return true if the download manager is available
 */
public static boolean isDownloadManagerAvailable(Context context) {

 if (Build.VERSION.SDK_INT &gt;= Build.VERSION_CODES.GINGERBREAD) {
 return true;
 }
 return false;
}
</code></pre>
Method's name explains it all. Once you are sure <code>DownloadManager</code> is available, you can do something like this:
<pre><code>String url = &quot;url you want to download&quot;;
DownloadManager.Request request = new DownloadManager.Request(Uri.parse(url));
request.setDescription(&quot;Some descrition&quot;);
request.setTitle(&quot;Some title&quot;);
// in order for this if to run, you must use the android 3.2 to compile your app
if (Build.VERSION.SDK_INT &gt;= Build.VERSION_CODES.HONEYCOMB) {
 request.allowScanningByMediaScanner();
 request.setNotificationVisibility(DownloadManager.Request.VISIBILITY_VISIBLE_NOTIFY_COMPLETED);
}
request.setDestinationInExternalPublicDir(Environment.DIRECTORY_DOWNLOADS, &quot;name-of-the-file.ext&quot;);

// get download service and enqueue file
DownloadManager manager = (DownloadManager) getSystemService(Context.DOWNLOAD_SERVICE);
manager.enqueue(request);
</code></pre>
Download progress will be showing in the notification bar.
<h1>Final thoughts</h1>
First and second methods are just the tip of the iceberg. There are lots of things you have to keep in mind if you want your app to be robust. Here is a brief list:
<ul>
<li>You must check whether user has an internet connection available</li>
<li>Make sure you have the right permissions (<code>INTERNET</code> and <code>WRITE_EXTERNAL_STORAGE</code>); also <code>ACCESS_NETWORK_STATE</code> if you want to check internet availability.</li>
<li>Make sure the directory were you are going to download files exist and has write permissions.</li>
<li>If download is too big you may want to implement a way to resume the download if previous attempts failed.</li>
<li>Users will be grateful if you allow them to interrupt the download.</li>
</ul>
Unless you need detailed control of the download process, then consider using <code>DownloadManager</code> (3) because it already handles most of the items listed above.
But also consider that your needs may change. For example, <code>DownloadManager</code> <a href="https://stackoverflow.com/questions/35191718">does no response caching</a>. It will blindly download the same big file multiple times. There's no easy way to fix it after the fact. Where if you start with a basic <code>HttpURLConnection</code> (1, 2), then all you need is to add an <code>HttpResponseCache</code>. So the initial effort of learning the basic, standard tools can be a good investment.
<blockquote>
This class was deprecated in API level 26. ProgressDialog is a modal
dialog, which prevents the user from interacting with the app. Instead
of using this class, you should use a progress indicator like
ProgressBar, which can be embedded in your app's UI. Alternatively,
you can use a notification to inform the user of the task's progress. For more details <a href="https://developer.android.com/reference/android/app/ProgressDialog" rel="noreferrer">Link</a>
</blockquote>

blocks|key|1754219|text|不要忘记添加权限到您的清单文件，如果您要下载的东西从互联网！|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1754220|<manifest+xmlns:android="http://schemas.android.com/apk/res/android"
++++package="com.example.helloandroid"
++++android:versionCode="1"
++++android:versionName="1.0">

++++++++<uses-sdk+android:minSdkVersion="10"+/>

++++++++<uses-permission+android:name="android.permission.WRITE_EXTERNAL_STORAGE"></uses-permission>
++++++++<uses-permission+android:name="android.permission.INTERNET"></uses-permission>
++++++++<uses-permission+android:name="android.permission.ACCESS_NETWORK_STATE"></uses-permission>
++++++++<uses-permission+android:name="android.permission.READ_PHONE_STATE"></uses-permission>

++++++++<application+
++++++++++++android:icon="@drawable/icon"+
++++++++++++android:label="@string/app_name"+
++++++++++++android:debuggable="true">

++++++++</application>

</manifest>|code-block|syntax|javascript|1754221|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

Don't forget to add permissions to your manifest file if you're gonna be downloading stuff from the internet!

<pre><code>&lt;manifest xmlns:android="http://schemas.android.com/apk/res/android"
 package="com.example.helloandroid"
 android:versionCode="1"
 android:versionName="1.0"&gt;

 &lt;uses-sdk android:minSdkVersion="10" /&gt;

 &lt;uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"&gt;&lt;/uses-permission&gt;
 &lt;uses-permission android:name="android.permission.INTERNET"&gt;&lt;/uses-permission&gt;
 &lt;uses-permission android:name="android.permission.ACCESS_NETWORK_STATE"&gt;&lt;/uses-permission&gt;
 &lt;uses-permission android:name="android.permission.READ_PHONE_STATE"&gt;&lt;/uses-permission&gt;

 &lt;application 
 android:icon="@drawable/icon" 
 android:label="@string/app_name" 
 android:debuggable="true"&gt;

 &lt;/application&gt;

&lt;/manifest&gt;
</code></pre>

blocks|key|1754255|text|是的，如果您正在onProgressUpdate+of+Asynctask中更新您的progressbar，并且您按后退按钮或完成您的活动AsyncTask，则上面的代码将在返回您的活动时使用UI+.And松散其跟踪，即使下载在后台运行，您也不会看到进度条上的任何更新。因此，在OnResume()上，尝试使用一个计时器任务运行一个像runOnUIThread这样的线程，通过从运行中的AsyncTask后台更新值来更新您的progressbar。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|1754256|private+void+updateProgressBar(){
++++Runnable+runnable+=+new+updateProgress();
++++background+=+new+Thread(runnable);
++++background.start();
}

public+class+updateProgress+implements+Runnable+{
++++public+void+run()+{
++++++++while(Thread.currentThread()==background)
++++++++++++//while+(!Thread.currentThread().isInterrupted())+{
++++++++++++try+{
++++++++++++++++Thread.sleep(1000);+
++++++++++++++++Message+msg+=+new+Message();
++++++++++++++++progress+=+getProgressPercentage();++++++++
++++++++++++++++handler.sendMessage(msg);
++++++++++++}+catch+(InterruptedException+e)+{
++++++++++++++++Thread.currentThread().interrupt();
++++++++++++}+catch+(Exception+e)+{
++++++++}
++++}
}

private+Handler+handler+=+new+Handler(){
++++@Override
++++public+void+handleMessage(Message+msg)+{
++++++++progress.setProgress(msg.what);
++++}
};|code-block|syntax|javascript|1754257|当您的活动不可见时，不要忘记销毁线程。|BOLD|1754258|private+void+destroyRunningThreads()+{
++++if+(background+!=+null)+{
++++++++background.interrupt();
++++++++background=null;
++++}
}|1754259|entityMap^0|8|G|S|9|16|B|1X|9|3V|A|4N|D|5D|9|5W|B|0|0|E|4|0|0^^$0|@$1|2|3|4|5|6|7|R|8|@$9|S|A|T|B|C]|$9|U|A|V|B|C]|$9|W|A|X|B|C]|$9|Y|A|Z|B|C]|$9|10|A|11|B|C]|$9|12|A|13|B|C]|$9|14|A|15|B|C]|$9|16|A|17|B|C]]|D|@]|E|$]]|$1|F|3|G|5|H|7|18|8|@]|D|@]|E|$I|J]]|$1|K|3|L|5|6|7|19|8|@$9|1A|A|1B|B|M]]|D|@]|E|$]]|$1|N|3|O|5|H|7|1C|8|@]|D|@]|E|$I|J]]|$1|P|3|-4|5|6|7|1D|8|@]|D|@]|E|$]]]|Q|$]]

Yes the code above will work .But if you are updating your <code>progressbar</code> in <code>onProgressUpdate</code> of <code>Asynctask</code> and you press back button or finish your activity <code>AsyncTask</code> looses its track with your UI .And when you go back to your activity, even if download is running in background you will see no update on progressbar. So on <code>OnResume()</code> try to run a thread like <code>runOnUIThread</code> with a timer task that updates ur <code>progressbar</code> with values updating from the <code>AsyncTask</code> running background.

<pre><code>private void updateProgressBar(){
 Runnable runnable = new updateProgress();
 background = new Thread(runnable);
 background.start();
}

public class updateProgress implements Runnable {
 public void run() {
 while(Thread.currentThread()==background)
 //while (!Thread.currentThread().isInterrupted()) {
 try {
 Thread.sleep(1000); 
 Message msg = new Message();
 progress = getProgressPercentage(); 
 handler.sendMessage(msg);
 } catch (InterruptedException e) {
 Thread.currentThread().interrupt();
 } catch (Exception e) {
 }
 }
}

private Handler handler = new Handler(){
 @Override
 public void handleMessage(Message msg) {
 progress.setProgress(msg.what);
 }
};
</code></pre>

Don't forget to Destroy the thread when ur activity is not visible.

<pre><code>private void destroyRunningThreads() {
 if (background != null) {
 background.interrupt();
 background=null;
 }
}
</code></pre>

blocks|key|1406988|text|我个人的建议是使用进度对话框并在执行前进行构建，或者在OnPreExecute()上启动，如果您使用进度对话框的进度条的水平样式，则经常发布进度。最后对doInBackground算法进行了优化。|type|unstyled|depth|inlineStyleRanges|offset|length|style|BOLD|CODE|entityRanges|data|1406989|entityMap^0|9|5|R|E|24|E|0^^$0|@$1|2|3|4|5|6|7|I|8|@$9|J|A|K|B|C]|$9|L|A|M|B|D]|$9|N|A|O|B|D]]|E|@]|F|$]]|$1|G|3|-4|5|6|7|P|8|@]|E|@]|F|$]]]|H|$]]

My personal advice is to use Progress Dialog and build up before execution , or initiate at <code>OnPreExecute()</code> , publish progress often if you use horizontal style of progress bar of the progress dialog. The remaining part is to optimize the algorithm of <code>doInBackground</code>.

blocks|key|1754332|text|别忘了用“/sdcard.”代替新文件(“/mnt/sdcard/.”)否则你会得到一个FileNotFoundException|type|unstyled|depth|inlineStyleRanges|offset|length|style|BOLD|entityRanges|data|1754333|entityMap^0|G|3|18|L|0^^$0|@$1|2|3|4|5|6|7|H|8|@$9|I|A|J|B|C]|$9|K|A|L|B|C]]|D|@]|E|$]]|$1|F|3|-4|5|6|7|M|8|@]|D|@]|E|$]]]|G|$]]

Do not forget to replace "/sdcard..." by new File("/mnt/sdcard/...") otherwise you will get a FileNotFoundException

blocks|key|1407031|text|我建议您使用我的项目Netroid，它是基于截击的。我已经添加了一些功能，如多事件回调，文件下载管理。这可能会有帮助。|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|1407032|entityMap|0|LINK|mutability|MUTABLE|url|https://github.com/vince-styling/Netroid|1|https://www.captechconsulting.com/blog/raymond-robinson/google-io-2013-volley-image-cache-tutorial^0|A|7|0|M|2|1|0^^$0|@$1|2|3|4|5|6|7|N|8|@]|9|@$A|O|B|P|1|Q]|$A|R|B|S|1|T]]|C|$]]|$1|D|3|-4|5|6|7|U|8|@]|9|@]|C|$]]]|E|$F|$5|G|H|I|C|$J|K]]|L|$5|G|H|I|C|$J|M]]]]

I'd recommend you to use my Project <a href="https://github.com/vince-styling/Netroid" rel="noreferrer">Netroid</a>, It's based on <a href="https://www.captechconsulting.com/blog/raymond-robinson/google-io-2013-volley-image-cache-tutorial" rel="noreferrer">Volley</a>. I have added some features to it such as multi-events callback, file download management. This could be of some help.

blocks|key|1754379|text|当我开始学习android开发的时候，我已经了解到ProgressDialog是前进的道路。在下载文件时，可以调用ProgressDialog的ProgressDialog方法来更新进度级别。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|1754380|我在许多应用程序中看到的最好的是，它们自定义这个进度对话框的属性，以给进度对话框提供比股票版本更好的外观和感觉。好让用户参与一些像青蛙，大象或可爱的猫/小狗的动画。任何在进度对话框中的动画都吸引着用户，他们不想等待太久。|1754381|entityMap^0|P|E|1L|E|20|E|0|0^^$0|@$1|2|3|4|5|6|7|J|8|@$9|K|A|L|B|C]|$9|M|A|N|B|C]|$9|O|A|P|B|C]]|D|@]|E|$]]|$1|F|3|G|5|6|7|Q|8|@]|D|@]|E|$]]|$1|H|3|-4|5|6|7|R|8|@]|D|@]|E|$]]]|I|$]]

While I was starting to learn android development, I had learnt that <code>ProgressDialog</code> is the way to go. There is the <code>setProgress</code> method of <code>ProgressDialog</code> which can be invoked to update the progress level as the file gets downloaded.

The best I have seen in many apps is that they customize this progress dialog's attributes to give a better look and feel to the progress dialog than the stock version. Good to keeping the user engaged with some animation of like frog, elephant or cute cats/puppies. Any animation with in the progress dialog attracts users and they don't feel like being kept waiting for long.

blocks|key|1754402|text|我已经修改了AsyncTask类，以便在相同的上下文中处理progressDialog的创建，.I认为下面的代码将更加可重用。(它可以从任何活动中调用，只需传递上下文、目标文件、对话框消息)|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|1754403|public+static+class+DownloadTask+extends+AsyncTask<String,+Integer,+String>+{
++++private+ProgressDialog+mPDialog;
++++private+Context+mContext;
++++private+PowerManager.WakeLock+mWakeLock;
++++private+File+mTargetFile;
++++//Constructor+parameters+:
++++//+@context+(current+Activity)
++++//+@targetFile+(File+object+to+write,it+will+be+overwritten+if+exist)
++++//+@dialogMessage+(message+of+the+ProgresDialog)
++++public+DownloadTask(Context+context,File+targetFile,String+dialogMessage)+{
++++++++this.mContext+=+context;
++++++++this.mTargetFile+=+targetFile;
++++++++mPDialog+=+new+ProgressDialog(context);

++++++++mPDialog.setMessage(dialogMessage);
++++++++mPDialog.setIndeterminate(true);
++++++++mPDialog.setProgressStyle(ProgressDialog.STYLE_HORIZONTAL);
++++++++mPDialog.setCancelable(true);
++++++++//+reference+to+instance+to+use+inside+listener
++++++++final+DownloadTask+me+=+this;
++++++++mPDialog.setOnCancelListener(new+DialogInterface.OnCancelListener()+{
++++++++++++@Override
++++++++++++public+void+onCancel(DialogInterface+dialog)+{
++++++++++++++++me.cancel(true);
++++++++++++}
++++++++});
++++++++Log.i("DownloadTask","Constructor+done");
++++}

++++@Override
++++protected+String+doInBackground(String...+sUrl)+{
++++++++InputStream+input+=+null;
++++++++OutputStream+output+=+null;
++++++++HttpURLConnection+connection+=+null;
++++++++try+{
++++++++++++URL+url+=+new+URL(sUrl[0]);
++++++++++++connection+=+(HttpURLConnection)+url.openConnection();
++++++++++++connection.connect();

++++++++++++//+expect+HTTP+200+OK,+so+we+don't+mistakenly+save+error+report
++++++++++++//+instead+of+the+file
++++++++++++if+(connection.getResponseCode()+!=+HttpURLConnection.HTTP_OK)+{
++++++++++++++++return+"Server+returned+HTTP+"+%2B+connection.getResponseCode()
++++++++++++++++++++++++%2B+"+"+%2B+connection.getResponseMessage();
++++++++++++}
++++++++++++Log.i("DownloadTask","Response+"+%2B+connection.getResponseCode());

++++++++++++//+this+will+be+useful+to+display+download+percentage
++++++++++++//+might+be+-1:+server+did+not+report+the+length
++++++++++++int+fileLength+=+connection.getContentLength();

++++++++++++//+download+the+file
++++++++++++input+=+connection.getInputStream();
++++++++++++output+=+new+FileOutputStream(mTargetFile,false);

++++++++++++byte+data[]+=+new+byte[4096];
++++++++++++long+total+=+0;
++++++++++++int+count;
++++++++++++while+((count+=+input.read(data))+!=+-1)+{
++++++++++++++++//+allow+canceling+with+back+button
++++++++++++++++if+(isCancelled())+{
++++++++++++++++++++Log.i("DownloadTask","Cancelled");
++++++++++++++++++++input.close();
++++++++++++++++++++return+null;
++++++++++++++++}
++++++++++++++++total+%2B=+count;
++++++++++++++++//+publishing+the+progress....
++++++++++++++++if+(fileLength+>+0)+//+only+if+total+length+is+known
++++++++++++++++++++publishProgress((int)+(total+*+100+/+fileLength));
++++++++++++++++output.write(data,+0,+count);
++++++++++++}
++++++++}+catch+(Exception+e)+{
++++++++++++return+e.toString();
++++++++}+finally+{
++++++++++++try+{
++++++++++++++++if+(output+!=+null)
++++++++++++++++++++output.close();
++++++++++++++++if+(input+!=+null)
++++++++++++++++++++input.close();
++++++++++++}+catch+(IOException+ignored)+{
++++++++++++}

++++++++++++if+(connection+!=+null)
++++++++++++++++connection.disconnect();
++++++++}
++++++++return+null;
++++}
++++@Override
++++protected+void+onPreExecute()+{
++++++++super.onPreExecute();
++++++++//+take+CPU+lock+to+prevent+CPU+from+going+off+if+the+user
++++++++//+presses+the+power+button+during+download
++++++++PowerManager+pm+=+(PowerManager)+mContext.getSystemService(Context.POWER_SERVICE);
++++++++mWakeLock+=+pm.newWakeLock(PowerManager.PARTIAL_WAKE_LOCK,
++++++++++++++++getClass().getName());
++++++++mWakeLock.acquire();

++++++++mPDialog.show();

++++}

++++@Override
++++protected+void+onProgressUpdate(Integer...+progress)+{
++++++++super.onProgressUpdate(progress);
++++++++//+if+we+get+here,+length+is+known,+now+set+indeterminate+to+false
++++++++mPDialog.setIndeterminate(false);
++++++++mPDialog.setMax(100);
++++++++mPDialog.setProgress(progress[0]);

++++}

++++@Override
++++protected+void+onPostExecute(String+result)+{
++++++++Log.i("DownloadTask",+"Work+Done!+PostExecute");
++++++++mWakeLock.release();
++++++++mPDialog.dismiss();
++++++++if+(result+!=+null)
++++++++++++Toast.makeText(mContext,"Download+error:+"%2Bresult,+Toast.LENGTH_LONG).show();
++++++++else
++++++++++++Toast.makeText(mContext,"File+Downloaded",+Toast.LENGTH_SHORT).show();
++++}
}|code-block|syntax|javascript|1754404|entityMap^0|6|9|T|E|0|0^^$0|@$1|2|3|4|5|6|7|M|8|@$9|N|A|O|B|C]|$9|P|A|Q|B|C]]|D|@]|E|$]]|$1|F|3|G|5|H|7|R|8|@]|D|@]|E|$I|J]]|$1|K|3|-4|5|6|7|S|8|@]|D|@]|E|$]]]|L|$]]

I have modified <code>AsyncTask</code> class to handle creation of <code>progressDialog</code> at the same context .I think following code will be more reusable.
(it can be called from any activity just pass context,target File,dialog message)

<pre><code>public static class DownloadTask extends AsyncTask&lt;String, Integer, String&gt; {
 private ProgressDialog mPDialog;
 private Context mContext;
 private PowerManager.WakeLock mWakeLock;
 private File mTargetFile;
 //Constructor parameters :
 // @context (current Activity)
 // @targetFile (File object to write,it will be overwritten if exist)
 // @dialogMessage (message of the ProgresDialog)
 public DownloadTask(Context context,File targetFile,String dialogMessage) {
 this.mContext = context;
 this.mTargetFile = targetFile;
 mPDialog = new ProgressDialog(context);

 mPDialog.setMessage(dialogMessage);
 mPDialog.setIndeterminate(true);
 mPDialog.setProgressStyle(ProgressDialog.STYLE_HORIZONTAL);
 mPDialog.setCancelable(true);
 // reference to instance to use inside listener
 final DownloadTask me = this;
 mPDialog.setOnCancelListener(new DialogInterface.OnCancelListener() {
 @Override
 public void onCancel(DialogInterface dialog) {
 me.cancel(true);
 }
 });
 Log.i("DownloadTask","Constructor done");
 }

 @Override
 protected String doInBackground(String... sUrl) {
 InputStream input = null;
 OutputStream output = null;
 HttpURLConnection connection = null;
 try {
 URL url = new URL(sUrl[0]);
 connection = (HttpURLConnection) url.openConnection();
 connection.connect();

 // expect HTTP 200 OK, so we don't mistakenly save error report
 // instead of the file
 if (connection.getResponseCode() != HttpURLConnection.HTTP_OK) {
 return "Server returned HTTP " + connection.getResponseCode()
 + " " + connection.getResponseMessage();
 }
 Log.i("DownloadTask","Response " + connection.getResponseCode());

 // this will be useful to display download percentage
 // might be -1: server did not report the length
 int fileLength = connection.getContentLength();

 // download the file
 input = connection.getInputStream();
 output = new FileOutputStream(mTargetFile,false);

 byte data[] = new byte[4096];
 long total = 0;
 int count;
 while ((count = input.read(data)) != -1) {
 // allow canceling with back button
 if (isCancelled()) {
 Log.i("DownloadTask","Cancelled");
 input.close();
 return null;
 }
 total += count;
 // publishing the progress....
 if (fileLength &gt; 0) // only if total length is known
 publishProgress((int) (total * 100 / fileLength));
 output.write(data, 0, count);
 }
 } catch (Exception e) {
 return e.toString();
 } finally {
 try {
 if (output != null)
 output.close();
 if (input != null)
 input.close();
 } catch (IOException ignored) {
 }

 if (connection != null)
 connection.disconnect();
 }
 return null;
 }
 @Override
 protected void onPreExecute() {
 super.onPreExecute();
 // take CPU lock to prevent CPU from going off if the user
 // presses the power button during download
 PowerManager pm = (PowerManager) mContext.getSystemService(Context.POWER_SERVICE);
 mWakeLock = pm.newWakeLock(PowerManager.PARTIAL_WAKE_LOCK,
 getClass().getName());
 mWakeLock.acquire();

 mPDialog.show();

 }

 @Override
 protected void onProgressUpdate(Integer... progress) {
 super.onProgressUpdate(progress);
 // if we get here, length is known, now set indeterminate to false
 mPDialog.setIndeterminate(false);
 mPDialog.setMax(100);
 mPDialog.setProgress(progress[0]);

 }

 @Override
 protected void onPostExecute(String result) {
 Log.i("DownloadTask", "Work Done! PostExecute");
 mWakeLock.release();
 mPDialog.dismiss();
 if (result != null)
 Toast.makeText(mContext,"Download error: "+result, Toast.LENGTH_LONG).show();
 else
 Toast.makeText(mContext,"File Downloaded", Toast.LENGTH_SHORT).show();
 }
}
</code></pre>

blocks|key|1754428|text|权限|type|unstyled|depth|inlineStyleRanges|offset|length|style|BOLD|entityRanges|data|1754429|++<uses-permission+android:name="android.permission.INTERNET"+/>
++<uses-permission+
+++android:name="android.permission.WRITE_EXTERNAL_STORAGE"+/>|code-block|syntax|javascript|1754430|使用HttpURLConnection|1754431|import+java.io.File;
import+java.io.FileOutputStream;
import+java.io.IOException;
import+java.io.InputStream;
import+java.net.HttpURLConnection;
import+java.net.MalformedURLException;
import+java.net.URL;

import+android.app.Activity;
import+android.app.Dialog;
import+android.os.Bundle;
import+android.os.Environment;
import+android.view.View;
import+android.view.Window;
import+android.view.View.OnClickListener;
import+android.widget.Button;
import+android.widget.ProgressBar;
import+android.widget.TextView;
import+android.widget.Toast;

public+class+DownloadFileUseHttpURLConnection+extends+Activity+{

ProgressBar+pb;
Dialog+dialog;
int+downloadedSize+=+0;
int+totalSize+=+0;
TextView+cur_val;
String+dwnload_file_path+=++
"http://coderzheaven.com/sample_folder/sample_file.png";
@Override
public+void+onCreate(Bundle+savedInstanceState)+{
++++super.onCreate(savedInstanceState);
++++setContentView(R.layout.main);

++++Button+b+=+(Button)+findViewById(R.id.b1);
++++b.setOnClickListener(new+OnClickListener()+{
++++++++@Override
++++++++public+void+onClick(View+v)+{
+++++++++++++showProgress(dwnload_file_path);

++++++++++++++++new+Thread(new+Runnable()+{
++++++++++++++++++++public+void+run()+{
+++++++++++++++++++++++++downloadFile();
++++++++++++++++++++}
++++++++++++++++++}).start();
++++++++}
++++});
}

void+downloadFile(){

++++try+{
++++++++URL+url+=+new+URL(dwnload_file_path);
++++++++HttpURLConnection+urlConnection+=+(HttpURLConnection)+++
+url.openConnection();

++++++++urlConnection.setRequestMethod("GET");
++++++++urlConnection.setDoOutput(true);

++++++++//connect
++++++++urlConnection.connect();

++++++++//set+the+path+where+we+want+to+save+the+file+++++++++++
++++++++File+SDCardRoot+=+Environment.getExternalStorageDirectory();+
++++++++//create+a+new+file,+to+save+the+downloaded+file+
++++++++File+file+=+new+File(SDCardRoot,"downloaded_file.png");

++++++++FileOutputStream+fileOutput+=+new+FileOutputStream(file);

++++++++//Stream+used+for+reading+the+data+from+the+internet
++++++++InputStream+inputStream+=+urlConnection.getInputStream();

++++++++//this+is+the+total+size+of+the+file+which+we+are+downloading
++++++++totalSize+=+urlConnection.getContentLength();

++++++++runOnUiThread(new+Runnable()+{
++++++++++++public+void+run()+{
++++++++++++++++pb.setMax(totalSize);
++++++++++++}+++++++++++++++
++++++++});

++++++++//create+a+buffer...
++++++++byte[]+buffer+=+new+byte[1024];
++++++++int+bufferLength+=+0;

++++++++while+(+(bufferLength+=+inputStream.read(buffer))+>+0+)+{
++++++++++++fileOutput.write(buffer,+0,+bufferLength);
++++++++++++downloadedSize+%2B=+bufferLength;
++++++++++++//+update+the+progressbar+//
++++++++++++runOnUiThread(new+Runnable()+{
++++++++++++++++public+void+run()+{
++++++++++++++++++++pb.setProgress(downloadedSize);
++++++++++++++++++++float+per+=+((float)downloadedSize/totalSize)+*+++++
++++++++++++++++++++100;
++++++++++++++++++++cur_val.setText("Downloaded+"+%2B+downloadedSize+%2B++

++++++++++++++++++++"KB+/+"+%2B+totalSize+%2B+"KB+("+%2B+(int)per+%2B+"%25)"+);
++++++++++++++++}
++++++++++++});
++++++++}
++++++++//close+the+output+stream+when+complete+//
++++++++fileOutput.close();
++++++++runOnUiThread(new+Runnable()+{
++++++++++++public+void+run()+{
++++++++++++++++//+pb.dismiss();+//+if+you+want+close+it..
++++++++++++}
++++++++});+++++++++

++++}+catch+(final+MalformedURLException+e)+{
++++++++showError("Error+:+MalformedURLException+"+%2B+e);++++++++
++++++++e.printStackTrace();
++++}+catch+(final+IOException+e)+{
++++++++showError("Error+:+IOException+"+%2B+e);++++++++++
++++++++e.printStackTrace();
++++}
++++catch+(final+Exception+e)+{
++++++++showError("Error+:+Please+check+your+internet+connection+"+%2B++
e);
++++}+++++++
}

void+showError(final+String+err){
++++runOnUiThread(new+Runnable()+{
++++++++public+void+run()+{
++++++++++++Toast.makeText(DownloadFileDemo1.this,+err,++
++++++Toast.LENGTH_LONG).show();
++++++++}
++++});
}

void+showProgress(String+file_path){
++++dialog+=+new+Dialog(DownloadFileDemo1.this);
++++dialog.requestWindowFeature(Window.FEATURE_NO_TITLE);
++++dialog.setContentView(R.layout.myprogressdialog);
++++dialog.setTitle("Download+Progress");

++++TextView+text+=+(TextView)+dialog.findViewById(R.id.tv1);
++++text.setText("Downloading+file+from+...+"+%2B+file_path);
++++cur_val+=+(TextView)+dialog.findViewById(R.id.cur_pg_tv);
++++cur_val.setText("Starting+download...");
++++dialog.show();

+++++pb+=+(ProgressBar)dialog.findViewById(R.id.progress_bar);
+++++pb.setProgress(0);
++++++++++++pb.setProgressDrawable(
++++++getResources().getDrawable(R.drawable.green_progress));++
++}
}|1754432|entityMap^0|0|2|0|0|2|H|0|0^^$0|@$1|2|3|4|5|6|7|Q|8|@$9|R|A|S|B|C]]|D|@]|E|$]]|$1|F|3|G|5|H|7|T|8|@]|D|@]|E|$I|J]]|$1|K|3|L|5|6|7|U|8|@$9|V|A|W|B|C]]|D|@]|E|$]]|$1|M|3|N|5|H|7|X|8|@]|D|@]|E|$I|J]]|$1|O|3|-4|5|6|7|Y|8|@]|D|@]|E|$]]]|P|$]]

Permissions

<pre><code> &lt;uses-permission android:name="android.permission.INTERNET" /&gt;
 &lt;uses-permission 
 android:name="android.permission.WRITE_EXTERNAL_STORAGE" /&gt;
</code></pre>

Using HttpURLConnection

<pre><code>import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.net.HttpURLConnection;
import java.net.MalformedURLException;
import java.net.URL;

import android.app.Activity;
import android.app.Dialog;
import android.os.Bundle;
import android.os.Environment;
import android.view.View;
import android.view.Window;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.ProgressBar;
import android.widget.TextView;
import android.widget.Toast;

public class DownloadFileUseHttpURLConnection extends Activity {

ProgressBar pb;
Dialog dialog;
int downloadedSize = 0;
int totalSize = 0;
TextView cur_val;
String dwnload_file_path = 
"http://coderzheaven.com/sample_folder/sample_file.png";
@Override
public void onCreate(Bundle savedInstanceState) {
 super.onCreate(savedInstanceState);
 setContentView(R.layout.main);

 Button b = (Button) findViewById(R.id.b1);
 b.setOnClickListener(new OnClickListener() {
 @Override
 public void onClick(View v) {
 showProgress(dwnload_file_path);

 new Thread(new Runnable() {
 public void run() {
 downloadFile();
 }
 }).start();
 }
 });
}

void downloadFile(){

 try {
 URL url = new URL(dwnload_file_path);
 HttpURLConnection urlConnection = (HttpURLConnection) 
 url.openConnection();

 urlConnection.setRequestMethod("GET");
 urlConnection.setDoOutput(true);

 //connect
 urlConnection.connect();

 //set the path where we want to save the file 
 File SDCardRoot = Environment.getExternalStorageDirectory(); 
 //create a new file, to save the downloaded file 
 File file = new File(SDCardRoot,"downloaded_file.png");

 FileOutputStream fileOutput = new FileOutputStream(file);

 //Stream used for reading the data from the internet
 InputStream inputStream = urlConnection.getInputStream();

 //this is the total size of the file which we are downloading
 totalSize = urlConnection.getContentLength();

 runOnUiThread(new Runnable() {
 public void run() {
 pb.setMax(totalSize);
 } 
 });

 //create a buffer...
 byte[] buffer = new byte[1024];
 int bufferLength = 0;

 while ( (bufferLength = inputStream.read(buffer)) &gt; 0 ) {
 fileOutput.write(buffer, 0, bufferLength);
 downloadedSize += bufferLength;
 // update the progressbar //
 runOnUiThread(new Runnable() {
 public void run() {
 pb.setProgress(downloadedSize);
 float per = ((float)downloadedSize/totalSize) * 
 100;
 cur_val.setText("Downloaded " + downloadedSize + 

 "KB / " + totalSize + "KB (" + (int)per + "%)" );
 }
 });
 }
 //close the output stream when complete //
 fileOutput.close();
 runOnUiThread(new Runnable() {
 public void run() {
 // pb.dismiss(); // if you want close it..
 }
 }); 

 } catch (final MalformedURLException e) {
 showError("Error : MalformedURLException " + e); 
 e.printStackTrace();
 } catch (final IOException e) {
 showError("Error : IOException " + e); 
 e.printStackTrace();
 }
 catch (final Exception e) {
 showError("Error : Please check your internet connection " + 
e);
 } 
}

void showError(final String err){
 runOnUiThread(new Runnable() {
 public void run() {
 Toast.makeText(DownloadFileDemo1.this, err, 
 Toast.LENGTH_LONG).show();
 }
 });
}

void showProgress(String file_path){
 dialog = new Dialog(DownloadFileDemo1.this);
 dialog.requestWindowFeature(Window.FEATURE_NO_TITLE);
 dialog.setContentView(R.layout.myprogressdialog);
 dialog.setTitle("Download Progress");

 TextView text = (TextView) dialog.findViewById(R.id.tv1);
 text.setText("Downloading file from ... " + file_path);
 cur_val = (TextView) dialog.findViewById(R.id.cur_pg_tv);
 cur_val.setText("Starting download...");
 dialog.show();

 pb = (ProgressBar)dialog.findViewById(R.id.progress_bar);
 pb.setProgress(0);
 pb.setProgressDrawable(
 getResources().getDrawable(R.drawable.green_progress)); 
 }
}
</code></pre>

blocks|key|1405546|text|我正在为我现在使用的其他解决方案添加另一个答案，因为Android查询太大了，无法维护以保持健康。所以我搬到了这个https://github.com/amitshekhariitbhu/Fast-Android-Networking。|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|1405547|++++AndroidNetworking.download(url,dirPath,fileName).build()
++++++.setDownloadProgressListener(new+DownloadProgressListener()+{
++++++++public+void+onProgress(long+bytesDownloaded,+long+totalBytes)+{
++++++++++++bar.setMax((int)+totalBytes);
++++++++++++bar.setProgress((int)+bytesDownloaded);
++++++++}
++++}).startDownload(new+DownloadListener()+{
++++++++public+void+onDownloadComplete()+{
++++++++++++...
++++++++}

++++++++public+void+onError(ANError+error)+{
++++++++++++...
++++++++}
++++});|code-block|syntax|javascript|1405548|entityMap|0|LINK|mutability|MUTABLE|url|https://github.com/amitshekhariitbhu/Fast-Android-Networking^0|1L|1O|0|0|0^^$0|@$1|2|3|4|5|6|7|Q|8|@]|9|@$A|R|B|S|1|T]]|C|$]]|$1|D|3|E|5|F|7|U|8|@]|9|@]|C|$G|H]]|$1|I|3|-4|5|6|7|V|8|@]|9|@]|C|$]]]|J|$K|$5|L|M|N|C|$O|P]]]]

I am adding another answer for other solution I am using now because Android Query is so big and unmaintained to stay healthy. So i moved to this <a href="https://github.com/amitshekhariitbhu/Fast-Android-Networking" rel="nofollow noreferrer">https://github.com/amitshekhariitbhu/Fast-Android-Networking</a>.

<pre><code> AndroidNetworking.download(url,dirPath,fileName).build()
 .setDownloadProgressListener(new DownloadProgressListener() {
 public void onProgress(long bytesDownloaded, long totalBytes) {
 bar.setMax((int) totalBytes);
 bar.setProgress((int) bytesDownloaded);
 }
 }).startDownload(new DownloadListener() {
 public void onDownloadComplete() {
 ...
 }

 public void onError(ANError error) {
 ...
 }
 });
</code></pre>

blocks|key|1754467|text|重要|type|unstyled|depth|inlineStyleRanges|offset|length|style|BOLD|entityRanges|data|1754468|AsyncTask在Android+11.中被废弃。|1754469|欲了解更多信息，请查看以下帖子|1754470|安卓的AsyncTask+API在Android11中不受欢迎，有什么可供选择的？|unordered-list-item|1754471|https://developer.android.com/reference/android/os/AsyncTask|1754472|可能应该像google建议的那样移到一致性框架|1754473|entityMap|0|LINK|mutability|MUTABLE|url|https://stackoverflow.com/q/58767733/9640177|1^0|0|2|0|0|L|0|0|0|15|0|0|0|1O|1|0|0^^$0|@$1|2|3|4|5|6|7|Z|8|@$9|10|A|11|B|C]]|D|@]|E|$]]|$1|F|3|G|5|6|7|12|8|@$9|13|A|14|B|C]]|D|@]|E|$]]|$1|H|3|I|5|6|7|15|8|@]|D|@]|E|$]]|$1|J|3|K|5|L|7|16|8|@]|D|@$9|17|A|18|1|19]]|E|$]]|$1|M|3|N|5|L|7|1A|8|@]|D|@$9|1B|A|1C|1|1D]]|E|$]]|$1|O|3|P|5|6|7|1E|8|@]|D|@]|E|$]]|$1|Q|3|-4|5|6|7|1F|8|@]|D|@]|E|$]]]|R|$S|$5|T|U|V|E|$W|X]]|Y|$5|T|U|V|E|$W|N]]]]

Important

AsyncTask is deprecated in Android 11.

For more information please checkout following posts

<ul>
<li><a href="https://stackoverflow.com/q/58767733/9640177">Android AsyncTask API deprecating in Android 11.What are the alternatives?</a></li>
<li><a href="https://developer.android.com/reference/android/os/AsyncTask" rel="nofollow noreferrer">https://developer.android.com/reference/android/os/AsyncTask</a></li>
</ul>

Probably should move to concorency Framework as suggested by google

blocks|key|204110|text|我们可以使用coroutine和工作经理在kotlin下载文件。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|204111|在build.gradle中添加依赖项|204112|++++implementation+"androidx.work:work-runtime-ktx:2.3.0-beta01"
++++implementation+"org.jetbrains.kotlinx:kotlinx-coroutines-android:1.3.1"|code-block|syntax|javascript|204113|WorkManager类|204114|++++import+android.content.Context
++++import+android.os.Environment
++++import+androidx.work.CoroutineWorker
++++import+androidx.work.WorkerParameters
++++import+androidx.work.workDataOf
++++import+com.sa.chat.utils.Const.BASE_URL_IMAGE
++++import+com.sa.chat.utils.Constants
++++import+kotlinx.coroutines.delay
++++import+java.io.BufferedInputStream
++++import+java.io.File
++++import+java.io.FileOutputStream
++++import+java.net.URL

++++class+DownloadMediaWorkManager(appContext:+Context,+workerParams:+WorkerParameters)
++++++++:+CoroutineWorker(appContext,+workerParams)+{

++++++++companion+object+{
++++++++++++const+val+WORK_TYPE+=+"WORK_TYPE"
++++++++++++const+val+WORK_IN_PROGRESS+=+"WORK_IN_PROGRESS"
++++++++++++const+val+WORK_PROGRESS_VALUE+=+"WORK_PROGRESS_VALUE"
++++++++}

++++++++override+suspend+fun+doWork():+Result+{

++++++++++++val+imageUrl+=+inputData.getString(Constants.WORK_DATA_MEDIA_URL)
++++++++++++val+imagePath+=+downloadMediaFromURL(imageUrl)

++++++++++++return+if+(!imagePath.isNullOrEmpty())+{
++++++++++++++++Result.success(workDataOf(Constants.WORK_DATA_MEDIA_URL+to+imagePath))
++++++++++++}+else+{
++++++++++++++++Result.failure()
++++++++++++}
++++++++}

++++++++private+suspend+fun+downloadMediaFromURL(imageUrl:+String?):+String?+{

++++++++++++val+file+=+File(
++++++++++++++++++++getRootFile().path,
++++++++++++++++++++"IMG_${System.currentTimeMillis()}.jpeg"
++++++++++++)

++++++++++++val+url+=+URL(BASE_URL_IMAGE+%2B+imageUrl)
++++++++++++val+connection+=+url.openConnection()
++++++++++++connection.connect()

++++++++++++val+lengthOfFile+=+connection.contentLength
++++++++++++//+download+the+file
++++++++++++val+input+=+BufferedInputStream(url.openStream(),+8192)
++++++++++++//+Output+stream
++++++++++++val+output+=+FileOutputStream(file)

++++++++++++val+data+=+ByteArray(1024)
++++++++++++var+total:+Long+=+0
++++++++++++var+last+=+0

++++++++++++while+(true)+{

++++++++++++++++val+count+=+input.read(data)
++++++++++++++++if+(count+==+-1)+break
++++++++++++++++total+%2B=+count.toLong()

++++++++++++++++val+progress+=+(total+*+100+/+lengthOfFile).toInt()

++++++++++++++++if+(progress+%25+10+==+0)+{
++++++++++++++++++++if+(last+!=+progress)+{
++++++++++++++++++++++++setProgress(workDataOf(WORK_TYPE+to+WORK_IN_PROGRESS,
++++++++++++++++++++++++++++++++WORK_PROGRESS_VALUE+to+progress))
++++++++++++++++++++}
++++++++++++++++++++last+=+progress
++++++++++++++++++++delay(50)
++++++++++++++++}
++++++++++++++++output.write(data,+0,+count)
++++++++++++}

++++++++++++output.flush()
++++++++++++output.close()
++++++++++++input.close()

++++++++++++return+file.path

++++++++}

++++++++private+fun+getRootFile():+File+{

++++++++++++val+rootDir+=+File(Environment.getExternalStorageDirectory().absolutePath+%2B+"/AppName")

++++++++++++if+(!rootDir.exists())+{
++++++++++++++++rootDir.mkdir()
++++++++++++}

++++++++++++val+dir+=+File("$rootDir/${Constants.IMAGE_FOLDER}/")

++++++++++++if+(!dir.exists())+{
++++++++++++++++dir.mkdir()
++++++++++++}
++++++++++++return+File(dir.absolutePath)
++++++++}
++++}|204115|开始在活动类中通过工作管理器下载|204116|+private+fun+downloadImage(imagePath:+String?,+id:+String)+{

++++++++++++val+data+=+workDataOf(WORK_DATA_MEDIA_URL+to+imagePath)
++++++++++++val+downloadImageWorkManager+=+OneTimeWorkRequestBuilder<DownloadMediaWorkManager>()
++++++++++++++++++++.setInputData(data)
++++++++++++++++++++.addTag(id)
++++++++++++++++++++.build()

++++++++++++WorkManager.getInstance(this).enqueue(downloadImageWorkManager)

++++++++++++WorkManager.getInstance(this).getWorkInfoByIdLiveData(downloadImageWorkManager.id)
++++++++++++++++++++.observe(this,+Observer+{+workInfo+->

++++++++++++++++++++++++if+(workInfo+!=+null)+{
++++++++++++++++++++++++++++when+{
++++++++++++++++++++++++++++++++workInfo.state+==+WorkInfo.State.SUCCEEDED+->+{
++++++++++++++++++++++++++++++++++++progressBar?.visibility+=+View.GONE
++++++++++++++++++++++++++++++++++++ivDownload?.visibility+=+View.GONE
++++++++++++++++++++++++++++++++}
++++++++++++++++++++++++++++++++workInfo.state+==+WorkInfo.State.FAILED+%7C%7C+workInfo.state+==+WorkInfo.State.CANCELLED+%7C%7C+workInfo.state+==+WorkInfo.State.BLOCKED+->+{
++++++++++++++++++++++++++++++++++++progressBar?.visibility+=+View.GONE
++++++++++++++++++++++++++++++++++++ivDownload?.visibility+=+View.VISIBLE
++++++++++++++++++++++++++++++++}
++++++++++++++++++++++++++++++++else+->+{
++++++++++++++++++++++++++++++++++++if(workInfo.progress.getString(WORK_TYPE)+==+WORK_IN_PROGRESS){
++++++++++++++++++++++++++++++++++++++++val+progress+=+workInfo.progress.getInt(WORK_PROGRESS_VALUE,+0)
++++++++++++++++++++++++++++++++++++++++progressBar?.visibility+=+View.VISIBLE
++++++++++++++++++++++++++++++++++++++++progressBar?.progress+=+progress
++++++++++++++++++++++++++++++++++++++++ivDownload?.visibility+=+View.GONE

++++++++++++++++++++++++++++++++++++}
++++++++++++++++++++++++++++++++}
++++++++++++++++++++++++++++}
++++++++++++++++++++++++}
++++++++++++++++++++})

++++++++}|204117|entityMap^0|0|0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|S|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|T|8|@]|9|@]|A|$]]|$1|D|3|E|5|F|7|U|8|@]|9|@]|A|$G|H]]|$1|I|3|J|5|6|7|V|8|@]|9|@]|A|$]]|$1|K|3|L|5|F|7|W|8|@]|9|@]|A|$G|H]]|$1|M|3|N|5|6|7|X|8|@]|9|@]|A|$]]|$1|O|3|P|5|F|7|Y|8|@]|9|@]|A|$G|H]]|$1|Q|3|-4|5|6|7|Z|8|@]|9|@]|A|$]]]|R|$]]

We can use the coroutine and work manager for downloading files in kotlin.

Add a dependency in build.gradle

<pre><code> implementation "androidx.work:work-runtime-ktx:2.3.0-beta01"
 implementation "org.jetbrains.kotlinx:kotlinx-coroutines-android:1.3.1"
</code></pre>

WorkManager class

<pre><code> import android.content.Context
 import android.os.Environment
 import androidx.work.CoroutineWorker
 import androidx.work.WorkerParameters
 import androidx.work.workDataOf
 import com.sa.chat.utils.Const.BASE_URL_IMAGE
 import com.sa.chat.utils.Constants
 import kotlinx.coroutines.delay
 import java.io.BufferedInputStream
 import java.io.File
 import java.io.FileOutputStream
 import java.net.URL

 class DownloadMediaWorkManager(appContext: Context, workerParams: WorkerParameters)
 : CoroutineWorker(appContext, workerParams) {

 companion object {
 const val WORK_TYPE = "WORK_TYPE"
 const val WORK_IN_PROGRESS = "WORK_IN_PROGRESS"
 const val WORK_PROGRESS_VALUE = "WORK_PROGRESS_VALUE"
 }

 override suspend fun doWork(): Result {

 val imageUrl = inputData.getString(Constants.WORK_DATA_MEDIA_URL)
 val imagePath = downloadMediaFromURL(imageUrl)

 return if (!imagePath.isNullOrEmpty()) {
 Result.success(workDataOf(Constants.WORK_DATA_MEDIA_URL to imagePath))
 } else {
 Result.failure()
 }
 }

 private suspend fun downloadMediaFromURL(imageUrl: String?): String? {

 val file = File(
 getRootFile().path,
 "IMG_${System.currentTimeMillis()}.jpeg"
 )

 val url = URL(BASE_URL_IMAGE + imageUrl)
 val connection = url.openConnection()
 connection.connect()

 val lengthOfFile = connection.contentLength
 // download the file
 val input = BufferedInputStream(url.openStream(), 8192)
 // Output stream
 val output = FileOutputStream(file)

 val data = ByteArray(1024)
 var total: Long = 0
 var last = 0

 while (true) {

 val count = input.read(data)
 if (count == -1) break
 total += count.toLong()

 val progress = (total * 100 / lengthOfFile).toInt()

 if (progress % 10 == 0) {
 if (last != progress) {
 setProgress(workDataOf(WORK_TYPE to WORK_IN_PROGRESS,
 WORK_PROGRESS_VALUE to progress))
 }
 last = progress
 delay(50)
 }
 output.write(data, 0, count)
 }

 output.flush()
 output.close()
 input.close()

 return file.path

 }

 private fun getRootFile(): File {

 val rootDir = File(Environment.getExternalStorageDirectory().absolutePath + "/AppName")

 if (!rootDir.exists()) {
 rootDir.mkdir()
 }

 val dir = File("$rootDir/${Constants.IMAGE_FOLDER}/")

 if (!dir.exists()) {
 dir.mkdir()
 }
 return File(dir.absolutePath)
 }
 }
</code></pre>

Start downloading through work manager in activity class 

<pre><code> private fun downloadImage(imagePath: String?, id: String) {

 val data = workDataOf(WORK_DATA_MEDIA_URL to imagePath)
 val downloadImageWorkManager = OneTimeWorkRequestBuilder&lt;DownloadMediaWorkManager&gt;()
 .setInputData(data)
 .addTag(id)
 .build()

 WorkManager.getInstance(this).enqueue(downloadImageWorkManager)

 WorkManager.getInstance(this).getWorkInfoByIdLiveData(downloadImageWorkManager.id)
 .observe(this, Observer { workInfo -&gt;

 if (workInfo != null) {
 when {
 workInfo.state == WorkInfo.State.SUCCEEDED -&gt; {
 progressBar?.visibility = View.GONE
 ivDownload?.visibility = View.GONE
 }
 workInfo.state == WorkInfo.State.FAILED || workInfo.state == WorkInfo.State.CANCELLED || workInfo.state == WorkInfo.State.BLOCKED -&gt; {
 progressBar?.visibility = View.GONE
 ivDownload?.visibility = View.VISIBLE
 }
 else -&gt; {
 if(workInfo.progress.getString(WORK_TYPE) == WORK_IN_PROGRESS){
 val progress = workInfo.progress.getInt(WORK_PROGRESS_VALUE, 0)
 progressBar?.visibility = View.VISIBLE
 progressBar?.progress = progress
 ivDownload?.visibility = View.GONE

 }
 }
 }
 }
 })

 }
</code></pre>

blocks|key|204119|text|++++private+class+DownloadTask+extends+AsyncTask<String,+Integer,+String>+{

++++++++private+PowerManager.WakeLock+mWakeLock;
++++++++String+onlinePathBundle,+onlinePathMusic,+offlinePathBundle,+offlinePathMusic;

++++++++CircleProgressBar+progressBar;
++++++++RelativeLayout+rl_progress;
++++++++ImageView+btn_download;
++++++++TextView+tv_progress;

++++++++public+DownloadTask(String+onlinePathBundle,+String+onlinePathMusic,+String+offlinePathBundle,+String+offlinePathMusic,+CircleProgressBar+progressBar,+RelativeLayout+rl_progress,+ImageView+btn_download,
++++++++++++++++++++++++++++TextView+tv_progress)+{
++++++++++++this.offlinePathBundle+=+offlinePathBundle;
++++++++++++this.offlinePathMusic+=+offlinePathMusic;
++++++++++++this.progressBar+=+progressBar;
++++++++++++this.rl_progress+=+rl_progress;
++++++++++++this.btn_download+=+btn_download;
++++++++++++this.tv_progress+=+tv_progress;
++++++++++++this.onlinePathBundle+=+onlinePathBundle;
++++++++++++this.onlinePathMusic+=+onlinePathMusic;
++++++++}

++++++++@Override
++++++++protected+void+onPreExecute()+{
++++++++++++super.onPreExecute();
++++++++++++progressBar.setMax(100);
++++++++++++rl_progress.setVisibility(View.VISIBLE);
++++++++++++btn_download.setVisibility(View.GONE);

++++++++++++PowerManager+pm+=+(PowerManager)+getSystemService(Context.POWER_SERVICE);
++++++++++++mWakeLock+=+pm.newWakeLock(PowerManager.PARTIAL_WAKE_LOCK,+getClass().getName());
++++++++++++mWakeLock.acquire();
++++++++}

++++++++@Override
++++++++protected+String+doInBackground(String...+sUrl)+{
++++++++++++String+firstResult+=+downTask(onlinePathBundle,+1,+offlinePathBundle);
++++++++++++String+seondResult+=+downTask(onlinePathMusic,+2,+offlinePathMusic);
++++++++++++if+(firstResult+!=+null)+{
++++++++++++++++Toast.makeText(SplashActivity.this,+"Download+error:+"+%2B+firstResult,+Toast.LENGTH_LONG).show();
++++++++++++++++return+firstResult;
++++++++++++}+else+{
++++++++++++++++return+seondResult;
++++++++++++}

++++++++}

++++++++@Override
++++++++protected+void+onProgressUpdate(Integer...+progress)+{
++++++++++++super.onProgressUpdate(progress);
++++++++++++progressBar.setProgress(progress[0]);
++++++++++++tv_progress.setText(progress[0]+%2B+"%25");

++++++++}

++++++++@Override
++++++++protected+void+onPostExecute(String+result)+{
++++++++++++super.onPostExecute(result);
++++++++++++rl_progress.setVisibility(View.GONE);
++++++++++++btn_download.setVisibility(View.VISIBLE);
++++++++++++if+(result+!=+null)+{
++++++++++++++++Toast.makeText(SplashActivity.this,+"Download+error:+"+%2B+result,+Toast.LENGTH_LONG).show();
++++++++++++}+else+{
++++++++++++++++rl_progress.setVisibility(View.GONE);
++++++++++++++++btn_download.setVisibility(View.GONE);
++++++++++++}

++++++++}

++++++++public+String+downTask(String+onlineNewPath,+int+numberOfTask,+String+offlineNewPath)+{
++++++++++++InputStream+input+=+null;
++++++++++++OutputStream+output+=+null;
++++++++++++HttpURLConnection+connection+=+null;
++++++++++++try+{
++++++++++++++++URL+url+=+new+URL(onlineNewPath);
++++++++++++++++connection+=+(HttpURLConnection)+url.openConnection();
++++++++++++++++connection.connect();

++++++++++++++++//+expect+HTTP+200+OK,+so+we+don't+mistakenly+save+error+report
++++++++++++++++//+instead+of+the+file
++++++++++++++++if+(connection.getResponseCode()+!=+HttpURLConnection.HTTP_OK)+{
++++++++++++++++++++return+"Server+returned+HTTP+"+%2B+connection.getResponseCode()
++++++++++++++++++++++++++++%2B+"+"+%2B+connection.getResponseMessage();
++++++++++++++++}

++++++++++++++++//+this+will+be+useful+to+display+download+percentage
++++++++++++++++//+might+be+-1:+server+did+not+report+the+length
++++++++++++++++int+fileLength+=+connection.getContentLength();

++++++++++++++++//+download+the+file
++++++++++++++++input+=+connection.getInputStream();
++++++++++++++++output+=+new+FileOutputStream(offlineNewPath);

++++++++++++++++byte+data[]+=+new+byte[4096];
++++++++++++++++long+total+=+0;
++++++++++++++++int+count;
++++++++++++++++while+((count+=+input.read(data))+!=+-1)+{
++++++++++++++++++++//+allow+canceling+with+back+button
++++++++++++++++++++if+(isCancelled())+{
++++++++++++++++++++++++input.close();
++++++++++++++++++++++++return+null;
++++++++++++++++++++}
++++++++++++++++++++total+%2B=+count;
++++++++++++++++++++//+publishing+the+progress....
++++++++++++++++++++if+(fileLength+>+0)+{//+only+if+total+length+is+known
++++++++++++++++++++++++if+(numberOfTask+==+1)+{
++++++++++++++++++++++++++++publishProgress((int)+(total+*+50+/+fileLength));
++++++++++++++++++++++++}+else+if+(numberOfTask+==+2)+{
++++++++++++++++++++++++++++publishProgress(((int)+(total+*+50+/+fileLength))+%2B+50);
++++++++++++++++++++++++}

++++++++++++++++++++}
++++++++++++++++++++output.write(data,+0,+count);
++++++++++++++++}
++++++++++++}+catch+(Exception+e)+{
++++++++++++++++return+e.toString();
++++++++++++}+finally+{
++++++++++++++++try+{
++++++++++++++++++++if+(output+!=+null)
++++++++++++++++++++++++output.close();
++++++++++++++++++++if+(input+!=+null)
++++++++++++++++++++++++input.close();
++++++++++++++++}+catch+(IOException+ignored)+{
++++++++++++++++}

++++++++++++++++if+(connection+!=+null)
++++++++++++++++++++connection.disconnect();
++++++++++++}
++++++++++++return+null;
++++++++}
++++}|type|code-block|depth|inlineStyleRanges|entityRanges|data|syntax|javascript|204120|unstyled|entityMap^0|0^^$0|@$1|2|3|4|5|6|7|G|8|@]|9|@]|A|$B|C]]|$1|D|3|-4|5|E|7|H|8|@]|9|@]|A|$]]]|F|$]]

<pre><code> private class DownloadTask extends AsyncTask&lt;String, Integer, String&gt; {

 private PowerManager.WakeLock mWakeLock;
 String onlinePathBundle, onlinePathMusic, offlinePathBundle, offlinePathMusic;

 CircleProgressBar progressBar;
 RelativeLayout rl_progress;
 ImageView btn_download;
 TextView tv_progress;

 public DownloadTask(String onlinePathBundle, String onlinePathMusic, String offlinePathBundle, String offlinePathMusic, CircleProgressBar progressBar, RelativeLayout rl_progress, ImageView btn_download,
 TextView tv_progress) {
 this.offlinePathBundle = offlinePathBundle;
 this.offlinePathMusic = offlinePathMusic;
 this.progressBar = progressBar;
 this.rl_progress = rl_progress;
 this.btn_download = btn_download;
 this.tv_progress = tv_progress;
 this.onlinePathBundle = onlinePathBundle;
 this.onlinePathMusic = onlinePathMusic;
 }

 @Override
 protected void onPreExecute() {
 super.onPreExecute();
 progressBar.setMax(100);
 rl_progress.setVisibility(View.VISIBLE);
 btn_download.setVisibility(View.GONE);

 PowerManager pm = (PowerManager) getSystemService(Context.POWER_SERVICE);
 mWakeLock = pm.newWakeLock(PowerManager.PARTIAL_WAKE_LOCK, getClass().getName());
 mWakeLock.acquire();
 }

 @Override
 protected String doInBackground(String... sUrl) {
 String firstResult = downTask(onlinePathBundle, 1, offlinePathBundle);
 String seondResult = downTask(onlinePathMusic, 2, offlinePathMusic);
 if (firstResult != null) {
 Toast.makeText(SplashActivity.this, &quot;Download error: &quot; + firstResult, Toast.LENGTH_LONG).show();
 return firstResult;
 } else {
 return seondResult;
 }

 }

 @Override
 protected void onProgressUpdate(Integer... progress) {
 super.onProgressUpdate(progress);
 progressBar.setProgress(progress[0]);
 tv_progress.setText(progress[0] + &quot;%&quot;);

 }

 @Override
 protected void onPostExecute(String result) {
 super.onPostExecute(result);
 rl_progress.setVisibility(View.GONE);
 btn_download.setVisibility(View.VISIBLE);
 if (result != null) {
 Toast.makeText(SplashActivity.this, &quot;Download error: &quot; + result, Toast.LENGTH_LONG).show();
 } else {
 rl_progress.setVisibility(View.GONE);
 btn_download.setVisibility(View.GONE);
 }

 }

 public String downTask(String onlineNewPath, int numberOfTask, String offlineNewPath) {
 InputStream input = null;
 OutputStream output = null;
 HttpURLConnection connection = null;
 try {
 URL url = new URL(onlineNewPath);
 connection = (HttpURLConnection) url.openConnection();
 connection.connect();

 // expect HTTP 200 OK, so we don't mistakenly save error report
 // instead of the file
 if (connection.getResponseCode() != HttpURLConnection.HTTP_OK) {
 return &quot;Server returned HTTP &quot; + connection.getResponseCode()
 + &quot; &quot; + connection.getResponseMessage();
 }

 // this will be useful to display download percentage
 // might be -1: server did not report the length
 int fileLength = connection.getContentLength();

 // download the file
 input = connection.getInputStream();
 output = new FileOutputStream(offlineNewPath);

 byte data[] = new byte[4096];
 long total = 0;
 int count;
 while ((count = input.read(data)) != -1) {
 // allow canceling with back button
 if (isCancelled()) {
 input.close();
 return null;
 }
 total += count;
 // publishing the progress....
 if (fileLength &gt; 0) {// only if total length is known
 if (numberOfTask == 1) {
 publishProgress((int) (total * 50 / fileLength));
 } else if (numberOfTask == 2) {
 publishProgress(((int) (total * 50 / fileLength)) + 50);
 }

 }
 output.write(data, 0, count);
 }
 } catch (Exception e) {
 return e.toString();
 } finally {
 try {
 if (output != null)
 output.close();
 if (input != null)
 input.close();
 } catch (IOException ignored) {
 }

 if (connection != null)
 connection.disconnect();
 }
 return null;
 }
 }
</code></pre>

blocks|key|1754544|text|我遇到了一个简单文件下载库获取，重要的是它具有存储访问框架、内容提供者和URI支持。如果有人还在搜索，可能会发现这很有帮助。|type|unstyled|depth|inlineStyleRanges|offset|length|style|BOLD|entityRanges|data|1754545|实现“androidx.tonyodev.stich2:x记忆体2:3.1.6”//AndroidX实现“com.tonyodev.get+2:+lib+2:3.0.12”/支持lib|blockquote|1754546|在不使用应用程序特定目录的情况下所需的权限。|1754547|<uses-permission+android:name="android.permission.WRITE_EXTERNAL_STORAGE"/>|CODE|1754548|<uses-permission+android:name="android.permission.READ_EXTERNAL_STORAGE"/>|1754549|互联网许可|1754550|<uses-permission+android:name="android.permission.INTERNET"/>|1754551|private+Fetch+fetch;
FetchConfiguration+fetchConfiguration+=+new+FetchConfiguration.Builder(this)
++++++++++++++++.setDownloadConcurrentLimit(3)//Concurrent+Download+limit
++++++++++++++++.build();

++++++++fetch+=+Fetch.Impl.getInstance(fetchConfiguration);

++++++++String+url+=+"http:www.example.com/test.txt";//URL+of+file
++++++++String+file+=+"/downloads/test.txt";//Path+of+file
++++++++
++++++++final+Request+request+=+new+Request(url,+file);
++++++++request.setPriority(Priority.HIGH);
++++++++request.setNetworkType(NetworkType.ALL);//Preferred+network+type
++++++++request.addHeader("clientKey",+"SD78DF93_3947&MVNGHE1WONG");//Auth+header+if+any
++++++++
++++++++fetch.enqueue(request,+updatedRequest+->+{
++++++++++++//Request+was+successfully+enqueued+for+download.
++++++++},+error+->+{
++++++++++++//An+error+occurred+enqueuing+the+request.
++++++++});

++++}|code-block|syntax|javascript|1754552|收听更新和进展情况|1754553|FetchListener+fetchListener+=+new+FetchListener()+{
++++@Override
++++public+void+onQueued(@NotNull+Download+download,+boolean+waitingOnNetwork)+{
++++++++if+(request.getId()+==+download.getId())+{
++++++++++++showDownloadInList(download);
++++++++}
++++}

++++@Override
++++public+void+onCompleted(@NotNull+Download+download)+{

++++}

++++@Override
++++public+void+onError(@NotNull+Download+download)+{
++++++++Error+error+=+download.getError();
++++}

++++@Override
++++public+void+onProgress(@NotNull+Download+download,+long+etaInMilliSeconds,+long+downloadedBytesPerSecond)+{
++++++++if+(request.getId()+==+download.getId())+{
++++++++++++updateDownload(download,+etaInMilliSeconds);
++++++++}
++++++++int+progress+=+download.getProgress();
++++}

++++@Override
++++public+void+onPaused(@NotNull+Download+download)+{

++++}

++++@Override
++++public+void+onResumed(@NotNull+Download+download)+{

++++}

++++@Override
++++public+void+onCancelled(@NotNull+Download+download)+{

++++}

++++@Override
++++public+void+onRemoved(@NotNull+Download+download)+{

++++}

++++@Override
++++public+void+onDeleted(@NotNull+Download+download)+{

++++}
};

fetch.addListener(fetchListener);

//Remove+listener+when+done.
fetch.removeListener(fetchListener);|1754554|此示例代码取自所有者页，所有信用都属于托诺·弗朗西斯|1754555|entityMap|0|LINK|mutability|MUTABLE|url|https://github.com/tonyofrancis/Fetch|1|https://github.com/tonyofrancis^0|6|6|N|6|U|5|10|3|D|2|0|0|0|0|0|23|0|0|22|0|0|0|1P|0|0|0|0|J|7|1|0^^$0|@$1|2|3|4|5|6|7|1E|8|@$9|1F|A|1G|B|C]|$9|1H|A|1I|B|C]|$9|1J|A|1K|B|C]|$9|1L|A|1M|B|C]]|D|@$9|1N|A|1O|1|1P]]|E|$]]|$1|F|3|G|5|H|7|1Q|8|@]|D|@]|E|$]]|$1|I|3|J|5|6|7|1R|8|@]|D|@]|E|$]]|$1|K|3|L|5|6|7|1S|8|@$9|1T|A|1U|B|M]]|D|@]|E|$]]|$1|N|3|O|5|6|7|1V|8|@$9|1W|A|1X|B|M]]|D|@]|E|$]]|$1|P|3|Q|5|6|7|1Y|8|@]|D|@]|E|$]]|$1|R|3|S|5|6|7|1Z|8|@$9|20|A|21|B|M]]|D|@]|E|$]]|$1|T|3|U|5|V|7|22|8|@]|D|@]|E|$W|X]]|$1|Y|3|Z|5|6|7|23|8|@]|D|@]|E|$]]|$1|10|3|11|5|V|7|24|8|@]|D|@]|E|$W|X]]|$1|12|3|13|5|6|7|25|8|@]|D|@$9|26|A|27|1|28]]|E|$]]|$1|14|3|-4|5|6|7|29|8|@]|D|@]|E|$]]]|15|$16|$5|17|18|19|E|$1A|1B]]|1C|$5|17|18|19|E|$1A|1D]]]]

I have came across a Simple File Download library
<a href="https://github.com/tonyofrancis/Fetch" rel="nofollow noreferrer">Fetch</a> and importantly it has Storage Access Framework, Content Provider and URI support. If anyone is still searching might found it helpful.
<blockquote>
implementation &quot;androidx.tonyodev.fetch2:xfetch2:3.1.6&quot; //AndroidX
</blockquote>
<blockquote>
implementation &quot;com.tonyodev.fetch2:fetch2:3.0.12&quot; //Support lib
</blockquote>
Required permissions in case your are not using app specific directory.
<code>&lt;uses-permission android:name=&quot;android.permission.WRITE_EXTERNAL_STORAGE&quot;/&gt;</code>
<code>&lt;uses-permission android:name=&quot;android.permission.READ_EXTERNAL_STORAGE&quot;/&gt;</code>
Internet permission
<code>&lt;uses-permission android:name=&quot;android.permission.INTERNET&quot;/&gt;</code>
<pre><code>private Fetch fetch;
FetchConfiguration fetchConfiguration = new FetchConfiguration.Builder(this)
 .setDownloadConcurrentLimit(3)//Concurrent Download limit
 .build();

 fetch = Fetch.Impl.getInstance(fetchConfiguration);

 String url = &quot;http:www.example.com/test.txt&quot;;//URL of file
 String file = &quot;/downloads/test.txt&quot;;//Path of file
 
 final Request request = new Request(url, file);
 request.setPriority(Priority.HIGH);
 request.setNetworkType(NetworkType.ALL);//Preferred network type
 request.addHeader(&quot;clientKey&quot;, &quot;SD78DF93_3947&amp;MVNGHE1WONG&quot;);//Auth header if any
 
 fetch.enqueue(request, updatedRequest -&gt; {
 //Request was successfully enqueued for download.
 }, error -&gt; {
 //An error occurred enqueuing the request.
 });

 }
</code></pre>
Listen for update and progress
<pre><code>FetchListener fetchListener = new FetchListener() {
 @Override
 public void onQueued(@NotNull Download download, boolean waitingOnNetwork) {
 if (request.getId() == download.getId()) {
 showDownloadInList(download);
 }
 }

 @Override
 public void onCompleted(@NotNull Download download) {

 }

 @Override
 public void onError(@NotNull Download download) {
 Error error = download.getError();
 }

 @Override
 public void onProgress(@NotNull Download download, long etaInMilliSeconds, long downloadedBytesPerSecond) {
 if (request.getId() == download.getId()) {
 updateDownload(download, etaInMilliSeconds);
 }
 int progress = download.getProgress();
 }

 @Override
 public void onPaused(@NotNull Download download) {

 }

 @Override
 public void onResumed(@NotNull Download download) {

 }

 @Override
 public void onCancelled(@NotNull Download download) {

 }

 @Override
 public void onRemoved(@NotNull Download download) {

 }

 @Override
 public void onDeleted(@NotNull Download download) {

 }
};

fetch.addListener(fetchListener);

//Remove listener when done.
fetch.removeListener(fetchListener);
</code></pre>
This example code is taken from the owner page all credit goes to <a href="https://github.com/tonyofrancis" rel="nofollow noreferrer">Tonyo Francis</a>

I am trying to write a simple application that gets updated. For this I need a simple function that can download a file and show the current progress in a <code>ProgressDialog</code>. I know how to do the <code>ProgressDialog</code>, but I'm not sure how to display the current progress and how to download the file in the first place.

Download a file with Android, and showing the progress in a ProgressDialog

翻译质量差，导致语言生硬或混乱。

没有提供实际的解决方法或示例。

解答不清晰，无法理解或解决问题。

页面排版不美观，阅读体验差。

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我正在尝试编写一个简单的应用程序来进行更新。为此，我需要一个可以下载文件并在ProgressDialog中显示当前进度的简单函数。我知道如何做ProgressDialog，但我不知道如何显示当前的进度，以及如何首先下载文件。

问下载一个使用Android的文件，并显示ProgressDialog中的进度
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问下载一个使用Android的文件，并显示ProgressDialog中的进度EN

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问下载一个使用Android的文件，并显示ProgressDialog中的进度
EN