Checking if an Android application is running in the background

Question

By background, I mean none of the application\'s activities are currently visible to the user?

Answer 1

I think this question should be more clear. When? Where? What is your specific situation you want to konw if your app is in background?

I just introduce my solution in my way.
I get this done by using the field "importance" of RunningAppProcessInfo class in every activity's onStop method in my app, which can be simply achieved by providing a BaseActivity for other activities to extend which implements the onStop method to check the value of "importance". Here is the code:

public static boolean isAppRunning(Context context) {
    ActivityManager activityManager = (ActivityManager) context
        .getSystemService(Context.ACTIVITY_SERVICE);
    List appProcesses = activityManager
        .getRunningAppProcesses();
    for (RunningAppProcessInfo appProcess : appProcesses) {
        if (appProcess.processName.equals(context.getPackageName())) {
            if (appProcess.importance != RunningAppProcessInfo.IMPORTANCE_PERCEPTIBLE) {
                return true;
            } 
        }
    }
    return false;
}