[Android] background application can know what the application currently running in the foreground

這是個一個舊時代的產物,超過 Android 4.4 (API 19) 以上有另一個寫法,小於等於 4.4 請服用:

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

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

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

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);

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

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

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

<uses-permission android:name="android.permission.GET_TASKS" />

from:

https://stackoverflow.com/questions/2166961/determining-the-current-foreground-application-from-a-background-task-or-service


基於上面的例子,加強版如下:

Something like,

class ForegroundCheckTask extends AsyncTask<Context, Void, Boolean> {

  @Override
  protected Boolean doInBackground(Context... params) {
    final Context context = params[0].getApplicationContext();
    return isAppOnForeground(context);
  }

  private boolean isAppOnForeground(Context context) {
    ActivityManager activityManager = (ActivityManager) context.getSystemService(Context.ACTIVITY_SERVICE);
    List<RunningAppProcessInfo> appProcesses = activityManager.getRunningAppProcesses();
    if (appProcesses == null) {
      return false;
    }
    final String packageName = context.getPackageName();
    for (RunningAppProcessInfo appProcess : appProcesses) {
      if (appProcess.importance == RunningAppProcessInfo.IMPORTANCE_FOREGROUND && appProcess.processName.equals(packageName)) {
        return true;
      }
    }
    return false;
  }
}

// Use like this:
boolean foregroud = new ForegroundCheckTask().execute(context).get();

以上是判斷自己的APP 有沒有在前景。


增加判斷 IMPORTANCE_VISIBLE 也沒什麼用…

The neatest and not deprecated way that I’ve found so far to do this, as follows:

@Override
public boolean foregrounded() {
    ActivityManager.RunningAppProcessInfo appProcessInfo = new ActivityManager.RunningAppProcessInfo();
    ActivityManager.getMyMemoryState(appProcessInfo);
    return (appProcessInfo.importance == IMPORTANCE_FOREGROUND || appProcessInfo.importance == IMPORTANCE_VISIBLE)
}

It only works with SDK 16+.

EDIT:

I removed the following code from the solution:

KeyguardManager km = (KeyguardManager) getSystemService(Context.KEYGUARD_SERVICE);
// App is foreground, but screen is locked, so show notification
return km.inKeyguardRestrictedInputMode();

since that makes not getting the notifications if the screen locked. I had a look to the framework and the purpose of this is not entirely clear. I’d remove it. Checking the process info state would be enough 🙂


最後是透過 的方法取得正確的前景App:

ActivityManager am = (ActivityManager)context.getSystemService(Context.ACTIVITY_SERVICE);
ComponentName cn = am.getRunningTasks(1).get(0).topActivity;
String currentPackageName = cn.getPackageName();

 

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