Android应用中是怎么判断程序是在前台运行还是在后台运行的

public static boolean Frontdesk(Context context) { ActivityManager activityManager = (ActivityManager) context   .getSystemService(Context.ACTIVITY_SERVICE); List<ActivityManager.RunningAppProcessInfo> appProcesses = activityManager   .getRunningAppProcesses(); for (ActivityManager.RunningAppProcessInfo appProcess : appProcesses) {  if (appProcess.processName.equals(context.getPackageName())) {   Log.i(context.getPackageName(), "此appimportace ="     + appProcess.importance     + ",context.getClass().getName()="     + context.getClass().getName());   if (appProcess.importance != ActivityManager.RunningAppProcessInfo.IMPORTANCE_FOREGROUND) {    Log.i(context.getPackageName(), "处于后台"      + appProcess.processName);    return true;   } else {    Log.i(context.getPackageName(), "处于前台"      + appProcess.processName);    return false;   }  } } return false;}