URL url = new URL("http://download.thinkbroadband.com/20MB.zip");
URLConnection connection = url.openConnection();
File fileThatExists = new File(path);
OutputStream output = new FileOutputStream(path, true);
connection.setRequestProperty("Range", "bytes=" + fileThatExists.length() + "-");
connection.connect();
int lenghtOfFile = connection.getContentLength();
InputStream input = new BufferedInputStream(url.openStream());
byte data[] = new byte[1024];
long total = 0;
while ((count = input.read(data)) != -1) {
total += count;
output.write(data, 0 , count);
}
在这段代码中,我尝试恢复下载。目标文件大小为20MB。但是当我在10mb上停止下载,然后继续下载,我得到文件大小为30MB的文件。它似乎继续写入文件,但不能从服务器下载部分。Wget -c可以很好地处理这个文件。如何恢复文件下载?
发布于 2011-06-13 00:21:44
HttpURLConnection connection = (HttpURLConnection) url.openConnection();
if(ISSUE_DOWNLOAD_STATUS.intValue()==ECMConstant.ECM_DOWNLOADING){
File file=new File(DESTINATION_PATH);
if(file.exists()){
downloaded = (int) file.length();
connection.setRequestProperty("Range", "bytes="+(file.length())+"-");
}
}else{
connection.setRequestProperty("Range", "bytes=" + downloaded + "-");
}
connection.setDoInput(true);
connection.setDoOutput(true);
progressBar.setMax(connection.getContentLength());
in = new BufferedInputStream(connection.getInputStream());
fos=(downloaded==0)? new FileOutputStream(DESTINATION_PATH): new FileOutputStream(DESTINATION_PATH,true);
bout = new BufferedOutputStream(fos, 1024);
byte[] data = new byte[1024];
int x = 0;
while ((x = in.read(data, 0, 1024)) >= 0) {
bout.write(data, 0, x);
downloaded += x;
progressBar.setProgress(downloaded);
}
这不是我的代码,但它可以工作。
发布于 2012-06-14 18:28:22
我猜您面临的问题是在url.openConnection()
之后调用url.openStream()
。
url.openStream()
等同于url.openConnection().getInputStream()
。因此,您将请求url两次。特别是第二次,它没有指定range属性。因此,下载总是从头开始。
您应该用connection.getInputStream()
替换url.openStream()
。
发布于 2018-06-05 13:21:53
这是我用来下载文件的块,更新用户界面的进度。
/*
* @param callback = To update the UI with appropriate action
* @param fileName = Name of the file by which downloaded file will be saved.
* @param downloadURL = File downloading URL
* @param filePath = Path where file will be saved
* @param object = Any object you want in return after download is completed to do certain operations like insert in DB or show toast
*/
public void startDownload(final IDownloadCallback callback, String fileName, String downloadURL, String filePath, Object object) {
callback.onPreExecute(); // Callback to tell that the downloading is going to start
int count = 0;
File outputFile = null; // Path where file will be downloaded
try {
File file = new File(filePath);
file.mkdirs();
long range = 0;
outputFile = new File(file, fileName);
/**
* Check whether the file exists or not
* If file doesn't exists then create the new file and range will be zero.
* But if file exists then get the length of file which will be the starting range,
* from where the file will be downloaded
*/
if (!outputFile.exists()) {
outputFile.createNewFile();
range = 0;
} else {
range = outputFile.length();
}
//Open the Connection
URL url = new URL(downloadURL);
URLConnection con = url.openConnection();
// Set the range parameter in header and give the range from where you want to start the downloading
con.setRequestProperty("Range", "bytes=" + range + "-");
/**
* The total length of file will be the total content length given by the server + range.
* Example: Suppose you have a file whose size is 1MB and you had already downloaded 500KB of it.
* Then you will pass in Header as "Range":"bytes=500000".
* Now the con.getContentLength() will be 500KB and range will be 500KB.
* So by adding the two you will get the total length of file which will be 1 MB
*/
final long lenghtOfFile = (int) con.getContentLength() + range;
FileOutputStream fileOutputStream = new FileOutputStream(outputFile, true);
InputStream inputStream = con.getInputStream();
byte[] buffer = new byte[1024];
long total = range;
/**
* Download the save the content into file
*/
while ((count = inputStream.read(buffer)) != -1) {
total += count;
int progress = (int) (total * 100 / lenghtOfFile);
EntityDownloadProgress entityDownloadProgress = new EntityDownloadProgress();
entityDownloadProgress.setProgress(progress);
entityDownloadProgress.setDownloadedSize(total);
entityDownloadProgress.setFileSize(lenghtOfFile);
callback.showProgress(entityDownloadProgress);
fileOutputStream.write(buffer, 0, count);
}
//Close the outputstream
fileOutputStream.close();
// Disconnect the Connection
if (con instanceof HttpsURLConnection) {
((HttpsURLConnection) con).disconnect();
} else if (con instanceof HttpURLConnection) {
((HttpURLConnection) con).disconnect();
}
inputStream.close();
/**
* If file size is equal then return callback as success with downlaoded filepath and the object
* else return failure
*/
if (lenghtOfFile == outputFile.length()) {
callback.onSuccess(outputFile.getAbsolutePath(), object);
} else {
callback.onFailure(object);
}
} catch (Exception e) {
e.printStackTrace();
callback.onFailure(object);
}
}
接口IDownloadCallback {
void onPreExecute(); // Callback to tell that the downloading is going to start
void onFailure(Object o); // Failed to download file
void onSuccess(String path, Object o); // Downloaded file successfully with downloaded path
void showProgress(EntityDownloadProgress entityDownloadProgress); // Show progress
}
公共类EntityDownloadProgress {
int progress; // range from 1-100
long fileSize;// Total size of file to be downlaoded
long downloadedSize; // Size of the downlaoded file
public void setProgress(int progress) {this.progress = progress;}
public void setFileSize(long fileSize) {this.fileSize = fileSize;}
public void setDownloadedSize(long downloadedSize) {this.downloadedSize = downloadedSize;}
}
https://stackoverflow.com/questions/6237079
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