Use the processLifeCyclerManager will solve your problem.
https://medium.com/trendyol-tech/android-architecture-components-processlifecycleowner-26aa905d4bc5

I have an android application, i need one function or any thing that can check if the app is closed not the activity is closed. I have an App like this, If you use App for 10 seconds, wherever you are in any activity, you will receive the notification “Time out”. I use the timer to do that, every thing work fine for the start. However, when I close app, the app must save the timeLeft for the next start. For example: If i have only 5 seconds left, then i close App. Next time i open the app, the timer will start from 5 seconds, not from 10 seconds. There are no problem if i stayed at WelcomeFirst (Activity which init the Timer), but if i go to next activity, the Timer will be canceled. I do not want that, The timer will only be canceld when the App is closed.

Is there a way to check if the App is closed or Activity is closed? I use ActivityLifecycleCallbacks and application class. I also try this function

private boolean isAppRunning() {
    ActivityManager m = (ActivityManager) this.getSystemService( ACTIVITY_SERVICE );
    List<ActivityManager.RunningTaskInfo> runningTaskInfoList =  m.getRunningTasks(10);
    Iterator<ActivityManager.RunningTaskInfo> itr = runningTaskInfoList.iterator();
    int n=0;
    while(itr.hasNext()){
        n++;
        itr.next();
    }
    if(n==1){ // App is killed
        return false;
    }

    return true; // App is in background or foreground
}

It doesn’t work.

My code

public class App extends Application implements Application.ActivityLifecycleCallbacks {

private Long START_TIME_IN_MILLIS  = 6000;
private  Boolean  mTimerRunning = false;
private Long mTimeLeftInMillis  = START_TIME_IN_MILLIS;
private  CountDownTimer mCountDownTimer;

@Override

public void onCreate() {
        super.onCreate();
       registerActivityLifecycleCallbacks(this);
    }
 @Override
    public void onActivityStarted(Activity activity) {

     //if the activity is WelcomeFirst then init the timer
      if (activity.localClassName == "WelcomeFirst") {
            SharedPreferences prefs = getSharedPreferences("prefsDay", Context.MODE_PRIVATE);
            mTimeLeftInMillis = prefs.getLong("millisLeft", 10000);
            mTimerRunning = prefs.getBoolean("timerRunning", false);
            startTimer();
        }
   
}

@Override
public void onActivityStopped(Activity activity) {

    //The code below mean if the Activity WelcomeFirst is closed then save the millisLeft for the next start.

if (activity.localClassName == "WelcomeFirst")  {
             mCountDownTimer.cancel();
              mTimerRunning = false;
            SharedPreferences prefs = getSharedPreferences("prefsDay", Context.MODE_PRIVATE);
            Editor editor = prefs.edit();
            editor.putLong("millisLeft", mTimeLeftInMillis);
            editor.putBoolean("timerRunning", mTimerRunning);
            editor.apply();
        }
       
     //I want to make the change. If The App is closed, then save the millisLeft for the next start.

     //Not the Activity is closed, then save the millisLeft for the next start
}

  private void startTimer() {
        mCountDownTimer = new CountDownTimer(mTimeLeftInMillis, 1000) {
            @Override
            public void onTick(long millisUntilFinished) {
                mTimeLeftInMillis = millisUntilFinished;
         
            }
        @Override
        public void onFinish() {
            mTimerRunning = false;
            Toast.makeText(this, "Time Out",Toast.LENGTH_SHORT).show()
        }

    }.start();
    mTimerRunning = true;
}