android app前後臺判斷

判斷是APP是否在後臺：

public static boolean isAppInBackground(Context context) {

        ActivityManager manager = (ActivityManager) context.getSystemService(Context.ACTIVITY_SERVICE);

        if (Build.VERSION.SDK_INT > Build.VERSION_CODES.LOLLIPOP) {

            List<ActivityManager.RunningAppProcessInfo> runningProcesses = manager.getRunningAppProcesses();

            if (!StringUtil.isListEmpty(runningProcesses)) {

                for (ActivityManager.RunningAppProcessInfo runningProcess : runningProcesses) {
                    if (runningProcess.importance == ActivityManager.RunningAppProcessInfo.IMPORTANCE_FOREGROUND) {
                        return false;
                    }
                }
            }
        } else {
            String myPackage = context.getPackageName();
            List<ActivityManager.RunningTaskInfo> task = manager.getRunningTasks(1);
            if (!StringUtil.isListEmpty(task)) {
                ComponentName info = task.get(0).topActivity;
                if (null != info) {
                    return !myPackage.equals(info.getPackageName());
                }
            }
        }
        return true;
    }

注意：在android5.0以上，只能判斷是否前後臺， 但是不能判斷app是否是在最上面的那個APP。因爲有可能有多個在前臺的APP。