blocks|key|3065036|text|ActivityManager类是查看哪些进程正在运行的合适工具。|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|3065037|要在后台运行，通常需要使用Service。|3065038|entityMap|0|LINK|mutability|MUTABLE|url|http://developer.android.com/reference/android/app/ActivityManager.html|1|http://developer.android.com/reference/android/app/Service.html^0|0|F|0|0|D|7|1|0^^$0|@$1|2|3|4|5|6|7|P|8|@]|9|@$A|Q|B|R|1|S]]|C|$]]|$1|D|3|E|5|6|7|T|8|@]|9|@$A|U|B|V|1|W]]|C|$]]|$1|F|3|-4|5|6|7|X|8|@]|9|@]|C|$]]]|G|$H|$5|I|J|K|C|$L|M]]|N|$5|I|J|K|C|$L|O]]]]

The <A HREF="http://developer.android.com/reference/android/app/ActivityManager.html" rel="noreferrer">ActivityManager</A> class is the appropriate tool to see which processes are running.

To run in the background, you typically want to use a <A HREF="http://developer.android.com/reference/android/app/Service.html" rel="noreferrer">Service</A>.

blocks|key|317957|text|这样做：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|317958|int+showLimit+=+20;

/*+Get+all+Tasks+available+(with+limit+set).+*/
ActivityManager+mgr+=+(ActivityManager)+getSystemService(Context.ACTIVITY_SERVICE);
List<ActivityManager.RunningTaskInfo>+allTasks+=+mgr.getRunningTasks(showLimit);
/*+Loop+through+all+tasks+returned.+*/
for+(ActivityManager.RunningTaskInfo+aTask+:+allTasks)+
{++++++++++++++++++
++++Log.i("MyApp",+"Task:+"+%2B+aTask.baseActivity.getClassName());+
++++if+(aTask.baseActivity.getClassName().equals("com.android.email.activity.MessageList"))+
++++++++running=true;
}|code-block|syntax|javascript|317959|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|$]]

Do something like this:

<pre><code>int showLimit = 20;

/* Get all Tasks available (with limit set). */
ActivityManager mgr = (ActivityManager) getSystemService(Context.ACTIVITY_SERVICE);
List&lt;ActivityManager.RunningTaskInfo&gt; allTasks = mgr.getRunningTasks(showLimit);
/* Loop through all tasks returned. */
for (ActivityManager.RunningTaskInfo aTask : allTasks) 
{ 
 Log.i("MyApp", "Task: " + aTask.baseActivity.getClassName()); 
 if (aTask.baseActivity.getClassName().equals("com.android.email.activity.MessageList")) 
 running=true;
}
</code></pre>

blocks|key|320883|text|尝试以下代码：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|320884|ActivityManager+activityManager+=+(ActivityManager)+newContext.getSystemService(+Context.ACTIVITY_SERVICE+);
List<RunningAppProcessInfo>+appProcesses+=+activityManager.getRunningAppProcesses();
for(RunningAppProcessInfo+appProcess+:+appProcesses){
++++if(appProcess.importance+==+RunningAppProcessInfo.IMPORTANCE_FOREGROUND){
++++++++Log.i("Foreground+App",+appProcess.processName);
++++}
}|code-block|syntax|javascript|320885|进程名是前台运行的应用的包名。将其与应用程序的包名进行比较。如果它是相同的，那么你的应用程序在前台运行。|320886|我希望这能回答你的问题。|320887|entityMap^0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|M|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|N|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|O|8|@]|9|@]|A|$]]|$1|I|3|J|5|6|7|P|8|@]|9|@]|A|$]]|$1|K|3|-4|5|6|7|Q|8|@]|9|@]|A|$]]]|L|$]]

Try the following code:

<pre><code>ActivityManager activityManager = (ActivityManager) newContext.getSystemService( Context.ACTIVITY_SERVICE );
List&lt;RunningAppProcessInfo&gt; appProcesses = activityManager.getRunningAppProcesses();
for(RunningAppProcessInfo appProcess : appProcesses){
 if(appProcess.importance == RunningAppProcessInfo.IMPORTANCE_FOREGROUND){
 Log.i("Foreground App", appProcess.processName);
 }
}
</code></pre>

Process name is the package name of the app running in foreground. Compare it to the package name of your application. If it is the same then your application is running on foreground.

I hope this answers your question.

blocks|key|320895|text|我不得不通过艰难的方式找到正确的解决方案。下面的代码是cyanogenmod7+(平板电脑调整)的一部分，并在Android2.3.3/+gingerbread上进行了测试。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|320896|方法：|320897|320898|getForegroundApp+-返回前台应用程序。|unordered-list-item|320899|getActivityForApp+-返回找到的应用程序的活动。|320900|isStillActive+-确定之前找到的应用程序是否仍为活动应用程序-+getForegroundApp|320901|的辅助函数|320902|这有望在所有方面回答这个问题(：|320903|private+RunningAppProcessInfo+getForegroundApp()+{
++++RunningAppProcessInfo+result=null,+info=null;

++++if(mActivityManager==null)
++++++++mActivityManager+=+(ActivityManager)mContext.getSystemService(Context.ACTIVITY_SERVICE);
++++List+<RunningAppProcessInfo>+l+=+mActivityManager.getRunningAppProcesses();
++++Iterator+<RunningAppProcessInfo>+i+=+l.iterator();
++++while(i.hasNext()){
++++++++info+=+i.next();
++++++++if(info.importance+==+RunningAppProcessInfo.IMPORTANCE_FOREGROUND
++++++++++++++++&&+!isRunningService(info.processName)){
++++++++++++result=info;
++++++++++++break;
++++++++}
++++}
++++return+result;
}

private+ComponentName+getActivityForApp(RunningAppProcessInfo+target){
++++ComponentName+result=null;
++++ActivityManager.RunningTaskInfo+info;

++++if(target==null)
++++++++return+null;

++++if(mActivityManager==null)
++++++++mActivityManager+=+(ActivityManager)mContext.getSystemService(Context.ACTIVITY_SERVICE);
++++List+<ActivityManager.RunningTaskInfo>+l+=+mActivityManager.getRunningTasks(9999);
++++Iterator+<ActivityManager.RunningTaskInfo>+i+=+l.iterator();

++++while(i.hasNext()){
++++++++info=i.next();
++++++++if(info.baseActivity.getPackageName().equals(target.processName)){
++++++++++++result=info.topActivity;
++++++++++++break;
++++++++}
++++}

++++return+result;
}

private+boolean+isStillActive(RunningAppProcessInfo+process,+ComponentName+activity)
{
++++//+activity+can+be+null+in+cases,+where+one+app+starts+another.+for+example,+astro
++++//+starting+rock+player+when+a+move+file+was+clicked.+we+dont+have+an+activity+then,
++++//+but+the+package+exits+as+soon+as+back+is+hit.+so+we+can+ignore+the+activity
++++//+in+this+case
++++if(process==null)
++++++++return+false;

++++RunningAppProcessInfo+currentFg=getForegroundApp();
++++ComponentName+currentActivity=getActivityForApp(currentFg);

++++if(currentFg!=null+&&+currentFg.processName.equals(process.processName)+&&
++++++++++++(activity==null+%7C%7C+currentActivity.compareTo(activity)==0))
++++++++return+true;

++++Slog.i(TAG,+"isStillActive+returns+false+-+CallerProcess:+"+%2B+process.processName+%2B+"+CurrentProcess:+"
++++++++++++%2B+(currentFg==null+?+"null"+:+currentFg.processName)+%2B+"+CallerActivity:"+%2B+(activity==null+?+"null"+:+activity.toString())
++++++++++++%2B+"+CurrentActivity:+"+%2B+(currentActivity==null+?+"null"+:+currentActivity.toString()));
++++return+false;
}

private+boolean+isRunningService(String+processname){
++++if(processname==null+%7C%7C+processname.isEmpty())
++++++++return+false;

++++RunningServiceInfo+service;

++++if(mActivityManager==null)
++++++++mActivityManager+=+(ActivityManager)mContext.getSystemService(Context.ACTIVITY_SERVICE);
++++List+<RunningServiceInfo>+l+=+mActivityManager.getRunningServices(9999);
++++Iterator+<RunningServiceInfo>+i+=+l.iterator();
++++while(i.hasNext()){
++++++++service+=+i.next();
++++++++if(service.process.equals(processname))
++++++++++++return+true;
++++}

++++return+false;
}|code-block|syntax|javascript|320904|entityMap^0|0|0|0|0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|W|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|X|8|@]|9|@]|A|$]]|$1|D|3|-4|5|6|7|Y|8|@]|9|@]|A|$]]|$1|E|3|F|5|G|7|Z|8|@]|9|@]|A|$]]|$1|H|3|I|5|G|7|10|8|@]|9|@]|A|$]]|$1|J|3|K|5|G|7|11|8|@]|9|@]|A|$]]|$1|L|3|M|5|6|7|12|8|@]|9|@]|A|$]]|$1|N|3|O|5|6|7|13|8|@]|9|@]|A|$]]|$1|P|3|Q|5|R|7|14|8|@]|9|@]|A|$S|T]]|$1|U|3|-4|5|6|7|15|8|@]|9|@]|A|$]]]|V|$]]

i had to figure out the right solution the hard way. the below code is part of cyanogenmod7 (the tablet tweaks) and is tested on android 2.3.3 / gingerbread. 

methods:

<ul>
<li>getForegroundApp - returns the foreground application. </li>
<li>getActivityForApp - returns the activity of the found app. </li>
<li>isStillActive - determines if a earlier found app is still the active app.</li>
<li>isRunningService - a helper function for getForegroundApp</li>
</ul>

this hopefully answers this issue in all extend (:

<pre><code>private RunningAppProcessInfo getForegroundApp() {
 RunningAppProcessInfo result=null, info=null;

 if(mActivityManager==null)
 mActivityManager = (ActivityManager)mContext.getSystemService(Context.ACTIVITY_SERVICE);
 List &lt;RunningAppProcessInfo&gt; l = mActivityManager.getRunningAppProcesses();
 Iterator &lt;RunningAppProcessInfo&gt; i = l.iterator();
 while(i.hasNext()){
 info = i.next();
 if(info.importance == RunningAppProcessInfo.IMPORTANCE_FOREGROUND
 &amp;&amp; !isRunningService(info.processName)){
 result=info;
 break;
 }
 }
 return result;
}

private ComponentName getActivityForApp(RunningAppProcessInfo target){
 ComponentName result=null;
 ActivityManager.RunningTaskInfo info;

 if(target==null)
 return null;

 if(mActivityManager==null)
 mActivityManager = (ActivityManager)mContext.getSystemService(Context.ACTIVITY_SERVICE);
 List &lt;ActivityManager.RunningTaskInfo&gt; l = mActivityManager.getRunningTasks(9999);
 Iterator &lt;ActivityManager.RunningTaskInfo&gt; i = l.iterator();

 while(i.hasNext()){
 info=i.next();
 if(info.baseActivity.getPackageName().equals(target.processName)){
 result=info.topActivity;
 break;
 }
 }

 return result;
}

private boolean isStillActive(RunningAppProcessInfo process, ComponentName activity)
{
 // activity can be null in cases, where one app starts another. for example, astro
 // starting rock player when a move file was clicked. we dont have an activity then,
 // but the package exits as soon as back is hit. so we can ignore the activity
 // in this case
 if(process==null)
 return false;

 RunningAppProcessInfo currentFg=getForegroundApp();
 ComponentName currentActivity=getActivityForApp(currentFg);

 if(currentFg!=null &amp;&amp; currentFg.processName.equals(process.processName) &amp;&amp;
 (activity==null || currentActivity.compareTo(activity)==0))
 return true;

 Slog.i(TAG, "isStillActive returns false - CallerProcess: " + process.processName + " CurrentProcess: "
 + (currentFg==null ? "null" : currentFg.processName) + " CallerActivity:" + (activity==null ? "null" : activity.toString())
 + " CurrentActivity: " + (currentActivity==null ? "null" : currentActivity.toString()));
 return false;
}

private boolean isRunningService(String processname){
 if(processname==null || processname.isEmpty())
 return false;

 RunningServiceInfo service;

 if(mActivityManager==null)
 mActivityManager = (ActivityManager)mContext.getSystemService(Context.ACTIVITY_SERVICE);
 List &lt;RunningServiceInfo&gt; l = mActivityManager.getRunningServices(9999);
 Iterator &lt;RunningServiceInfo&gt; i = l.iterator();
 while(i.hasNext()){
 service = i.next();
 if(service.process.equals(processname))
 return true;
 }

 return false;
}
</code></pre>

blocks|key|320919|text|关于"2.我的后台应用程序如何知道当前在前台运行的应用程序是什么“。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|320920|不要使用getRunningAppProcesses()方法，因为这会从我的经验中返回各种系统垃圾，并且您会得到多个具有RunningAppProcessInfo.IMPORTANCE_FOREGROUND的结果。请改用getRunningTasks()|offset|length|style|CODE|320921|这是我在我的服务中用来识别当前前台应用程序的代码，它非常简单：|320922|ActivityManager+am+=+(ActivityManager)+AppService.this.getSystemService(ACTIVITY_SERVICE);
//+The+first+in+the+list+of+RunningTasks+is+always+the+foreground+task.
RunningTaskInfo+foregroundTaskInfo+=+am.getRunningTasks(1).get(0);|code-block|syntax|javascript|320923|就这样，你就可以轻松地访问前台应用程序/活动的详细信息了：|320924|String+foregroundTaskPackageName+=+foregroundTaskInfo+.topActivity.getPackageName();
PackageManager+pm+=+AppService.this.getPackageManager();
PackageInfo+foregroundAppPackageInfo+=+pm.getPackageInfo(foregroundTaskPackageName,+0);
String+foregroundTaskAppName+=+foregroundAppPackageInfo.applicationInfo.loadLabel(pm).toString();|320925|这需要activity+menifest中的额外权限，并且可以完美地工作。|320926|<uses-permission+android:name="android.permission.GET_TASKS"+/>|320927|entityMap^0|0|4|O|1O|17|32|H|0|0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|Y|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|Z|8|@$D|10|E|11|F|G]|$D|12|E|13|F|G]|$D|14|E|15|F|G]]|9|@]|A|$]]|$1|H|3|I|5|6|7|16|8|@]|9|@]|A|$]]|$1|J|3|K|5|L|7|17|8|@]|9|@]|A|$M|N]]|$1|O|3|P|5|6|7|18|8|@]|9|@]|A|$]]|$1|Q|3|R|5|L|7|19|8|@]|9|@]|A|$M|N]]|$1|S|3|T|5|6|7|1A|8|@]|9|@]|A|$]]|$1|U|3|V|5|L|7|1B|8|@]|9|@]|A|$M|N]]|$1|W|3|-4|5|6|7|1C|8|@]|9|@]|A|$]]]|X|$]]

With regards to "2. How my background application can know what the application currently running in the foreground is." 

Do NOT use the <code>getRunningAppProcesses()</code> method as this returns all sorts of system rubbish from my experience and you'll get multiple results which have <code>RunningAppProcessInfo.IMPORTANCE_FOREGROUND</code>. Use <code>getRunningTasks()</code> instead

This is the code I use in my service to identify the current foreground application, its really easy:

<pre><code>ActivityManager am = (ActivityManager) AppService.this.getSystemService(ACTIVITY_SERVICE);
// The first in the list of RunningTasks is always the foreground task.
RunningTaskInfo foregroundTaskInfo = am.getRunningTasks(1).get(0);
</code></pre>

Thats it, then you can easily access details of the foreground app/activity:

<pre><code>String foregroundTaskPackageName = foregroundTaskInfo .topActivity.getPackageName();
PackageManager pm = AppService.this.getPackageManager();
PackageInfo foregroundAppPackageInfo = pm.getPackageInfo(foregroundTaskPackageName, 0);
String foregroundTaskAppName = foregroundAppPackageInfo.applicationInfo.loadLabel(pm).toString();
</code></pre>

This requires an additional permission in activity menifest and works perfectly.

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

blocks|key|319004|text|这对我很有效。但它只给出了主菜单名。也就是说，如果用户打开了“设置”-->“蓝牙”-->“设备名称”屏幕，RunningAppProcessInfo会将其称为“仅设置”。无法进一步深入|type|unstyled|depth|inlineStyleRanges|entityRanges|data|319005|ActivityManager+activityManager+=+(ActivityManager)+context.getSystemService(+Context.ACTIVITY_SERVICE+);
++++++++++++++++PackageManager+pm+=+context.getPackageManager();
++++++++++++++++List<RunningAppProcessInfo>+appProcesses+=+activityManager.getRunningAppProcesses();
++++++++++++++++for(RunningAppProcessInfo+appProcess+:+appProcesses)+{++++++++++++++
++++++++++++++++++++if(appProcess.importance+==+RunningAppProcessInfo.IMPORTANCE_FOREGROUND)+{
++++++++++++++++++++++++CharSequence+c+=+pm.getApplicationLabel(pm.getApplicationInfo(appProcess.processName,+PackageManager.GET_META_DATA));
++++++++++++++++++++++++Log.i("Foreground+App",+"package:+"+%2B+appProcess.processName+%2B+"+App:+"+%2B+c.toString());
++++++++++++++++++++}+++++++++++++++
++++++++++++++++}|code-block|syntax|javascript|319006|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|$]]

This worked for me. But it gives only the main menu name. That is if user has opened Settings --> Bluetooth --> Device Name screen, RunningAppProcessInfo calls it as just Settings. Not able to drill down furthur

<pre><code>ActivityManager activityManager = (ActivityManager) context.getSystemService( Context.ACTIVITY_SERVICE );
 PackageManager pm = context.getPackageManager();
 List&lt;RunningAppProcessInfo&gt; appProcesses = activityManager.getRunningAppProcesses();
 for(RunningAppProcessInfo appProcess : appProcesses) { 
 if(appProcess.importance == RunningAppProcessInfo.IMPORTANCE_FOREGROUND) {
 CharSequence c = pm.getApplicationLabel(pm.getApplicationInfo(appProcess.processName, PackageManager.GET_META_DATA));
 Log.i("Foreground App", "package: " + appProcess.processName + " App: " + c.toString());
 } 
 }
</code></pre>

blocks|key|315994|text|从棒棒糖开始，这种情况发生了变化。请在用户访问之前找到以下代码设置->安全->+(向下滚动到最后)具有usage+access+->的应用程序将权限授予我们的应用程序|type|unstyled|depth|inlineStyleRanges|entityRanges|data|315995|private+void+printForegroundTask()+{
++++String+currentApp+=+"NULL";
++++if(android.os.Build.VERSION.SDK_INT+>=+android.os.Build.VERSION_CODES.LOLLIPOP)+{
++++++++UsageStatsManager+usm+=+(UsageStatsManager)+this.getSystemService(Context.USAGE_STATS_SERVICE);
++++++++long+time+=+System.currentTimeMillis();
++++++++List<UsageStats>+appList+=+usm.queryUsageStats(UsageStatsManager.INTERVAL_DAILY,++time+-+1000*1000,+time);
++++++++if+(appList+!=+null+&&+appList.size()+>+0)+{
++++++++++++SortedMap<Long,+UsageStats>+mySortedMap+=+new+TreeMap<Long,+UsageStats>();
++++++++++++for+(UsageStats+usageStats+:+appList)+{
++++++++++++++++mySortedMap.put(usageStats.getLastTimeUsed(),+usageStats);
++++++++++++}
++++++++++++if+(mySortedMap+!=+null+&&+!mySortedMap.isEmpty())+{
++++++++++++++++currentApp+=+mySortedMap.get(mySortedMap.lastKey()).getPackageName();
++++++++++++}
++++++++}
++++}+else+{
++++++++ActivityManager+am+=+(ActivityManager)this.getSystemService(Context.ACTIVITY_SERVICE);
++++++++List<ActivityManager.RunningAppProcessInfo>+tasks+=+am.getRunningAppProcesses();
++++++++currentApp+=+tasks.get(0).processName;
++++}

++++Log.e(TAG,+"Current+App+in+foreground+is:+"+%2B+currentApp);
}|code-block|syntax|javascript|315996|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|$]]

From lollipop onwards this got changed. Please find below code, before that user has to go Settings -> Security -> (Scroll down to last) Apps with usage access -> Give the permissions to our app

<pre><code>private void printForegroundTask() {
 String currentApp = "NULL";
 if(android.os.Build.VERSION.SDK_INT &gt;= android.os.Build.VERSION_CODES.LOLLIPOP) {
 UsageStatsManager usm = (UsageStatsManager) this.getSystemService(Context.USAGE_STATS_SERVICE);
 long time = System.currentTimeMillis();
 List&lt;UsageStats&gt; appList = usm.queryUsageStats(UsageStatsManager.INTERVAL_DAILY, time - 1000*1000, time);
 if (appList != null &amp;&amp; appList.size() &gt; 0) {
 SortedMap&lt;Long, UsageStats&gt; mySortedMap = new TreeMap&lt;Long, UsageStats&gt;();
 for (UsageStats usageStats : appList) {
 mySortedMap.put(usageStats.getLastTimeUsed(), usageStats);
 }
 if (mySortedMap != null &amp;&amp; !mySortedMap.isEmpty()) {
 currentApp = mySortedMap.get(mySortedMap.lastKey()).getPackageName();
 }
 }
 } else {
 ActivityManager am = (ActivityManager)this.getSystemService(Context.ACTIVITY_SERVICE);
 List&lt;ActivityManager.RunningAppProcessInfo&gt; tasks = am.getRunningAppProcesses();
 currentApp = tasks.get(0).processName;
 }

 Log.e(TAG, "Current App in foreground is: " + currentApp);
}
</code></pre>

blocks|key|318054|text|在棒棒糖和更高的：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|318055|添加到mainfest：|318056|<uses-permission+android:name="android.permission.GET_TASKS"+/>|code-block|syntax|javascript|318057|然后做这样的事情：|318058|if(+mTaskId+<+0+)
{
++++List<AppTask>+tasks+=+mActivityManager.getAppTasks();+
++++if(+tasks.size()+>+0+)
++++++++mTaskId+=+tasks.get(+0+).getTaskInfo().id;
}|318059|entityMap^0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|O|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|P|8|@]|9|@]|A|$]]|$1|D|3|E|5|F|7|Q|8|@]|9|@]|A|$G|H]]|$1|I|3|J|5|6|7|R|8|@]|9|@]|A|$]]|$1|K|3|L|5|F|7|S|8|@]|9|@]|A|$G|H]]|$1|M|3|-4|5|6|7|T|8|@]|9|@]|A|$]]]|N|$]]

In lollipop and up:

Add to mainfest:

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

And do something like this:

<pre><code>if( mTaskId &lt; 0 )
{
 List&lt;AppTask&gt; tasks = mActivityManager.getAppTasks(); 
 if( tasks.size() &gt; 0 )
 mTaskId = tasks.get( 0 ).getTaskInfo().id;
}
</code></pre>

blocks|key|320972|text|这就是我检查我的应用程序是否在前台的方式。注意，我使用的是AsyncTask，正如官方安卓文档所建议的那样。|type|unstyled|depth|inlineStyleRanges|offset|length|style|BOLD|entityRanges|data|320973|`|320974|++++private+class+CheckIfForeground+extends+AsyncTask<Void,+Void,+Void>+{
++++@Override
++++protected+Void+doInBackground(Void...+voids)+{

++++++++ActivityManager+activityManager+=+(ActivityManager)+mContext.getSystemService(Context.ACTIVITY_SERVICE);
++++++++List<ActivityManager.RunningAppProcessInfo>+appProcesses+=+activityManager.getRunningAppProcesses();
++++++++for+(ActivityManager.RunningAppProcessInfo+appProcess+:+appProcesses)+{
++++++++++++if+(appProcess.importance+==+ActivityManager.RunningAppProcessInfo.IMPORTANCE_FOREGROUND)+{
++++++++++++++++Log.i("Foreground+App",+appProcess.processName);

++++++++++++++++if+(mContext.getPackageName().equalsIgnoreCase(appProcess.processName))+{
++++++++++++++++++++Log.i(Constants.TAG,+"foreground+true:"+%2B+appProcess.processName);
++++++++++++++++++++foreground+=+true;
++++++++++++++++++++//+close_app();
++++++++++++++++}
++++++++++++}
++++++++}
++++++++Log.d(Constants.TAG,+"foreground+value:"+%2B+foreground);
++++++++if+(foreground)+{
++++++++++++foreground+=+false;
++++++++++++close_app();
++++++++++++Log.i(Constants.TAG,+"Close+App+and+start+Activity:");

++++++++}+else+{
++++++++++++//if+not+foreground
++++++++++++close_app();
++++++++++++foreground+=+false;
++++++++++++Log.i(Constants.TAG,+"Close+App");

++++++++}

++++++++return+null;
++++}
}|code-block|syntax|javascript|320975|然后像这样执行AsyncTask。new+CheckIfForeground().execute();|CODE|320976|entityMap^0|T|9|15|4|0|0|0|H|Y|0^^$0|@$1|2|3|4|5|6|7|R|8|@$9|S|A|T|B|C]|$9|U|A|V|B|C]]|D|@]|E|$]]|$1|F|3|G|5|6|7|W|8|@]|D|@]|E|$]]|$1|H|3|I|5|J|7|X|8|@]|D|@]|E|$K|L]]|$1|M|3|N|5|6|7|Y|8|@$9|Z|A|10|B|O]]|D|@]|E|$]]|$1|P|3|-4|5|6|7|11|8|@]|D|@]|E|$]]]|Q|$]]

This is how I am checking if my app is in foreground. Note I am using AsyncTask as suggested by official Android documentation.`

`

<pre><code> private class CheckIfForeground extends AsyncTask&lt;Void, Void, Void&gt; {
 @Override
 protected Void doInBackground(Void... voids) {

 ActivityManager activityManager = (ActivityManager) mContext.getSystemService(Context.ACTIVITY_SERVICE);
 List&lt;ActivityManager.RunningAppProcessInfo&gt; appProcesses = activityManager.getRunningAppProcesses();
 for (ActivityManager.RunningAppProcessInfo appProcess : appProcesses) {
 if (appProcess.importance == ActivityManager.RunningAppProcessInfo.IMPORTANCE_FOREGROUND) {
 Log.i("Foreground App", appProcess.processName);

 if (mContext.getPackageName().equalsIgnoreCase(appProcess.processName)) {
 Log.i(Constants.TAG, "foreground true:" + appProcess.processName);
 foreground = true;
 // close_app();
 }
 }
 }
 Log.d(Constants.TAG, "foreground value:" + foreground);
 if (foreground) {
 foreground = false;
 close_app();
 Log.i(Constants.TAG, "Close App and start Activity:");

 } else {
 //if not foreground
 close_app();
 foreground = false;
 Log.i(Constants.TAG, "Close App");

 }

 return null;
 }
}
</code></pre>

and execute AsyncTask like this.<code>
new CheckIfForeground().execute();</code>

blocks|key|3278327|text|为了确定前台应用程序，你可以使用检测前台应用程序，你可以使用https://github.com/ricvalerio/foregroundappchecker。它根据设备的android版本使用不同的方法。|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|3278328|至于服务，repo还提供了您需要的代码。本质上，让android+studio为您创建服务，然后onCreate添加使用appChecker的代码片段。但是，您需要请求权限。|3278329|entityMap|0|LINK|mutability|MUTABLE|url|https://github.com/ricvalerio/foregroundappchecker^0|U|1E|0|0|0^^$0|@$1|2|3|4|5|6|7|N|8|@]|9|@$A|O|B|P|1|Q]]|C|$]]|$1|D|3|E|5|6|7|R|8|@]|9|@]|C|$]]|$1|F|3|-4|5|6|7|S|8|@]|9|@]|C|$]]]|G|$H|$5|I|J|K|C|$L|M]]]]

In order to determine the foreground application, you can use for detecting the foreground app, you can use <a href="https://github.com/ricvalerio/foregroundappchecker" rel="noreferrer">https://github.com/ricvalerio/foregroundappchecker</a>. It uses different methods depending on the android version of the device.

As for the service, the repo also provides the code you need for it. Essentially, let android studio create the service for you, and then onCreate add the snippet that uses the appChecker. You will need to request permission however.

blocks|key|319088|text|考虑到getRunningTasks()已被弃用，getRunningAppProcesses()也不可靠，我决定将StackOverflow中提到的两种方法结合起来：|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|319089|+++private+boolean+isAppInForeground(Context+context)
++++{
++++++++if+(Build.VERSION.SDK_INT+<+Build.VERSION_CODES.LOLLIPOP)
++++++++{
++++++++++++ActivityManager+am+=+(ActivityManager)+context.getSystemService(ACTIVITY_SERVICE);
++++++++++++ActivityManager.RunningTaskInfo+foregroundTaskInfo+=+am.getRunningTasks(1).get(0);
++++++++++++String+foregroundTaskPackageName+=+foregroundTaskInfo.topActivity.getPackageName();

++++++++++++return+foregroundTaskPackageName.toLowerCase().equals(context.getPackageName().toLowerCase());
++++++++}
++++++++else
++++++++{
++++++++++++ActivityManager.RunningAppProcessInfo+appProcessInfo+=+new+ActivityManager.RunningAppProcessInfo();
++++++++++++ActivityManager.getMyMemoryState(appProcessInfo);
++++++++++++if+(appProcessInfo.importance+==+IMPORTANCE_FOREGROUND+%7C%7C+appProcessInfo.importance+==+IMPORTANCE_VISIBLE)
++++++++++++{
++++++++++++++++return+true;
++++++++++++}

++++++++++++KeyguardManager+km+=+(KeyguardManager)+context.getSystemService(Context.KEYGUARD_SERVICE);
++++++++++++//+App+is+foreground,+but+screen+is+locked,+so+show+notification
++++++++++++return+km.inKeyguardRestrictedInputMode();
++++++++}
++++}|code-block|syntax|javascript|319090|entityMap^0|3|H|P|O|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|$]]

Taking into account that <code>getRunningTasks()</code> is deprecated and <code>getRunningAppProcesses()</code> is not reliable, I came to decision to combine 2 approaches mentioned in StackOverflow:

<pre><code> private boolean isAppInForeground(Context context)
 {
 if (Build.VERSION.SDK_INT &lt; Build.VERSION_CODES.LOLLIPOP)
 {
 ActivityManager am = (ActivityManager) context.getSystemService(ACTIVITY_SERVICE);
 ActivityManager.RunningTaskInfo foregroundTaskInfo = am.getRunningTasks(1).get(0);
 String foregroundTaskPackageName = foregroundTaskInfo.topActivity.getPackageName();

 return foregroundTaskPackageName.toLowerCase().equals(context.getPackageName().toLowerCase());
 }
 else
 {
 ActivityManager.RunningAppProcessInfo appProcessInfo = new ActivityManager.RunningAppProcessInfo();
 ActivityManager.getMyMemoryState(appProcessInfo);
 if (appProcessInfo.importance == IMPORTANCE_FOREGROUND || appProcessInfo.importance == IMPORTANCE_VISIBLE)
 {
 return true;
 }

 KeyguardManager km = (KeyguardManager) context.getSystemService(Context.KEYGUARD_SERVICE);
 // App is foreground, but screen is locked, so show notification
 return km.inKeyguardRestrictedInputMode();
 }
 }
</code></pre>

blocks|key|3065390|text|我将两个解决方案组合在一个方法中，它适用于我的API+24和API+21。其他的我没有测试过。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|3065391|Kotlin中的代码：|3065392|private+fun+isAppInForeground(context:+Context):+Boolean+{
++++val+appProcessInfo+=+ActivityManager.RunningAppProcessInfo()
++++ActivityManager.getMyMemoryState(appProcessInfo)
++++if+(appProcessInfo.importance+==+IMPORTANCE_FOREGROUND+%7C%7C
++++++++++++appProcessInfo.importance+==+IMPORTANCE_VISIBLE)+{
++++++++return+true
++++}+else+if+(appProcessInfo.importance+==+IMPORTANCE_TOP_SLEEPING+%7C%7C
++++++++++++appProcessInfo.importance+==+IMPORTANCE_BACKGROUND)+{
++++++++return+false
++++}

++++val+am+=+context.getSystemService(Context.ACTIVITY_SERVICE)+as+ActivityManager
++++val+foregroundTaskInfo+=+am.getRunningTasks(1)[0]
++++val+foregroundTaskPackageName+=+foregroundTaskInfo.topActivity.packageName
++++return+foregroundTaskPackageName.toLowerCase()+==+context.packageName.toLowerCase()
}|code-block|syntax|javascript|3065393|在Manifest中|3065394|
<uses-permission+android:name="android.permission.GET_TASKS"+/>|3065395|entityMap^0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|O|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|P|8|@]|9|@]|A|$]]|$1|D|3|E|5|F|7|Q|8|@]|9|@]|A|$G|H]]|$1|I|3|J|5|6|7|R|8|@]|9|@]|A|$]]|$1|K|3|L|5|F|7|S|8|@]|9|@]|A|$G|H]]|$1|M|3|-4|5|6|7|T|8|@]|9|@]|A|$]]]|N|$]]

I combined two solutions in one method and it works for me for API 24 and for API 21. Others I didn't test. 

The code in Kotlin: 

<pre><code>private fun isAppInForeground(context: Context): Boolean {
 val appProcessInfo = ActivityManager.RunningAppProcessInfo()
 ActivityManager.getMyMemoryState(appProcessInfo)
 if (appProcessInfo.importance == IMPORTANCE_FOREGROUND ||
 appProcessInfo.importance == IMPORTANCE_VISIBLE) {
 return true
 } else if (appProcessInfo.importance == IMPORTANCE_TOP_SLEEPING ||
 appProcessInfo.importance == IMPORTANCE_BACKGROUND) {
 return false
 }

 val am = context.getSystemService(Context.ACTIVITY_SERVICE) as ActivityManager
 val foregroundTaskInfo = am.getRunningTasks(1)[0]
 val foregroundTaskPackageName = foregroundTaskInfo.topActivity.packageName
 return foregroundTaskPackageName.toLowerCase() == context.packageName.toLowerCase()
}
</code></pre>

and in Manifest

<pre><code>&lt;!-- Check whether app in background or foreground --&gt;
&lt;uses-permission android:name="android.permission.GET_TASKS" /&gt;
</code></pre>

blocks|key|319143|text|当我们需要从我们自己的服务/后台线程检查我们的应用程序是否在前台时。这是我如何实现它的，它对我来说工作得很好：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|319144|public+class+TestApplication+extends+Application+implements+Application.ActivityLifecycleCallbacks+{

++++public+static+WeakReference<Activity>+foregroundActivityRef+=+null;

++++@Override
++++public+void+onActivityStarted(Activity+activity)+{
++++++++foregroundActivityRef+=+new+WeakReference<>(activity);
++++}

++++@Override
++++public+void+onActivityStopped(Activity+activity)+{
++++++++if+(foregroundActivityRef+!=+null+&&+foregroundActivityRef.get()+==+activity)+{
++++++++++++foregroundActivityRef+=+null;
++++++++}
++++}

++++//+IMPLEMENT+OTHER+CALLBACK+METHODS
}|code-block|syntax|javascript|319145|现在，要从其他类检查app是否在前台，只需调用：|319146|if(TestApplication.foregroundActivityRef!=null){
++++//+APP+IS+IN+FOREGROUND!
++++//+We+can+also+get+the+activity+that+is+currently+visible!
}|319147|更新(如+):所指出|offset|length|style|BOLD|319148|不要忘记在Application类的onCreate方法中注册回调。|CODE|319149|@Override
public+void+onCreate()+{
++++...
++++registerActivityLifecycleCallbacks(this);
}|319150|entityMap^0|0|0|0|0|0|4|5|2|0|I|8|0|0^^$0|@$1|2|3|4|5|6|7|X|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|Y|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|Z|8|@]|9|@]|A|$]]|$1|I|3|J|5|D|7|10|8|@]|9|@]|A|$E|F]]|$1|K|3|L|5|6|7|11|8|@$M|12|N|13|O|P]|$M|14|N|15|O|P]]|9|@]|A|$]]|$1|Q|3|R|5|6|7|16|8|@$M|17|N|18|O|S]]|9|@]|A|$]]|$1|T|3|U|5|D|7|19|8|@]|9|@]|A|$E|F]]|$1|V|3|-4|5|6|7|1A|8|@]|9|@]|A|$]]]|W|$]]

For cases when we need to check from our own service/background-thread whether our app is in foreground or not. This is how I implemented it, and it works fine for me:

<pre><code>public class TestApplication extends Application implements Application.ActivityLifecycleCallbacks {

 public static WeakReference&lt;Activity&gt; foregroundActivityRef = null;

 @Override
 public void onActivityStarted(Activity activity) {
 foregroundActivityRef = new WeakReference&lt;&gt;(activity);
 }

 @Override
 public void onActivityStopped(Activity activity) {
 if (foregroundActivityRef != null &amp;&amp; foregroundActivityRef.get() == activity) {
 foregroundActivityRef = null;
 }
 }

 // IMPLEMENT OTHER CALLBACK METHODS
}
</code></pre>

Now to check from other classes, whether app is in foreground or not, simply call:

<pre><code>if(TestApplication.foregroundActivityRef!=null){
 // APP IS IN FOREGROUND!
 // We can also get the activity that is currently visible!
}
</code></pre>

Update (as pointed out by <a href="https://stackoverflow.com/users/2641380/shs">SHS</a>):

Do not forget to register for the callbacks in your Application class's <code>onCreate</code> method.

<pre><code>@Override
public void onCreate() {
 ...
 registerActivityLifecycleCallbacks(this);
}
</code></pre>

blocks|key|321082|text|一个简单的解决方案是使用LiveData。创建一个单独的LiveData变量。(可能在一个普通的Kotlin文件中)。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|321083|val+foregroundHelper+=+MutableLiveData<Unit>()|code-block|syntax|javascript|321084|从活动或片段中观察：|321085|foregroundHelper.observe(this,+Observer+{})+//+for+Activity
foregroundHelper.observe(viewLifecycleOwner,+Observer+{})+//+for+Fragments|321086|现在从您的后台服务、广播接收器等：|321087|val+appIsVisibleToTheUser+=+foregroundHelper.hasActiveObservers()
//+Now+your+logic+goes.
if+(!appIsVisibleToUser)+{
+++//+App+is+in+background
+++//+So+In+my+case:
+++//+I'm+showing+Notification+to+the+user+for+the+error+happened+in+Background+Service.
}|321088|谢谢。|321089|entityMap^0|0|0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|S|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|T|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|U|8|@]|9|@]|A|$]]|$1|I|3|J|5|D|7|V|8|@]|9|@]|A|$E|F]]|$1|K|3|L|5|6|7|W|8|@]|9|@]|A|$]]|$1|M|3|N|5|D|7|X|8|@]|9|@]|A|$E|F]]|$1|O|3|P|5|6|7|Y|8|@]|9|@]|A|$]]|$1|Q|3|-4|5|6|7|Z|8|@]|9|@]|A|$]]]|R|$]]

An easy solution is to use LiveData.
Create a singleton LiveData variable. (probably in a plain Kotlin file).
<pre class="lang-kotlin prettyprint-override"><code>val foregroundHelper = MutableLiveData&lt;Unit&gt;()
</code></pre>
Observe From Activity or Fragment:
<pre class="lang-kotlin prettyprint-override"><code>foregroundHelper.observe(this, Observer {}) // for Activity
foregroundHelper.observe(viewLifecycleOwner, Observer {}) // for Fragments
</code></pre>
Now from Your Background Service, Broadcast Receiver, etc:
<pre class="lang-kotlin prettyprint-override"><code>val appIsVisibleToTheUser = foregroundHelper.hasActiveObservers()
// Now your logic goes.
if (!appIsVisibleToUser) {
 // App is in background
 // So In my case:
 // I'm showing Notification to the user for the error happened in Background Service.
}
</code></pre>
Thanks.

I wish to have one application that runs in the background, which knows when any of the built-in applications (messaging, contacts, etc) is running.

So my questions are:

<ol>
<li>How I should run my application in the background.</li>
<li>How my background application can know what the application currently running in the foreground is.</li>
</ol>

Responses from folks with experience would be greatly appreciated.

Determining the current foreground application from a background task or service

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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我希望有一个在后台运行的应用程序，它知道何时任何内置的应用程序(消息，联系人等)正在运行。所以我的问题是：我应该如何在background.How中运行我的应用程序后台应用程序可以知道当前在前台运行的应用程序是什么。有经验的人会非常感谢你的回复。

问从后台任务或服务确定当前前台应用
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问从后台任务或服务确定当前前台应用EN