how to continue timer in app when come back from onRestart state

Question

i've created a small app of memory game. in that app i have created a timer that show the time that take the user to finish the game. my problem is that the timer freeze after i go to another page (like home screen) and back to the game- the time remain at the same time it was stopped.....(i khnow it related somehow to onRestarte() method but dont know what to do..) i want that the timer will continue at the same time it has been stopped. (like if the user have an incall in the middle of the game and then want to continue).

    package com.example.kineret.memorygame;



    public class Game4x4Activity extends AppCompatActivity implements     View.OnClickListener{

    TextView timerTextView;
    long startTime = 0;
    Handler timerHandler = new Handler();
    Runnable timerRunnable = new Runnable() {
        @Override
        public void run() {
            long millis = System.currentTimeMillis() - startTime;
            int seconds = (int) (millis / 1000);
            int minutes = seconds / 60;
            seconds = seconds % 60;

            timerTextView.setText(String.format("%d:%02d", minutes, seconds));
            timerHandler.postDelayed(this, 500);
        }
    };

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_game4x4);
        timerTextView = (TextView) findViewById(R.id.timerTextView4x4);
    }

    @Override
    public void onPause() {
        super.onPause();
        timerHandler.removeCallbacks(timerRunnable);
    }


    @Override
    public void onClick(View view) {

        if(newGame) {
            startTime = System.currentTimeMillis();
            timerHandler.postDelayed(timerRunnable, 0);
            newGame = false;
        }

        // rest of my code...

}

Answer 1

i have edited your code. plz try this

public class Game4x4Activity extends AppCompatActivity implements     View.OnClickListener{

    // make a new variable
    static long elapsedTime = 0;
    TextView timerTextView;
    long startTime = 0;
    Handler timerHandler = new Handler();
    Runnable timerRunnable = new Runnable() {
        @Override
        public void run() {
            // change here
            long millis = (System.currentTimeMillis() - startTime) + elapsedTime;
            int seconds = (int) (millis / 1000);
            int minutes = seconds / 60;
            seconds = seconds % 60;

            timerTextView.setText(String.format("%d:%02d", minutes, seconds));
            timerHandler.postDelayed(this, 500);
        }
    };

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_game4x4);
        timerTextView = (TextView) findViewById(R.id.timerTextView4x4);
    }

    @Override
    public void onPause() {
        // change here
        elapsedTime = elapsedTime + (System.currentTimeMillis() - startTime);
        timerHandler.removeCallbacks(timerRunnable);
        super.onPause();
    }

    @Override
    public void onResume() {
        super.onResume();
        // change here
        if(!newGame) {
            startTime = System.currentTimeMillis();
            timerHandler.postDelayed(timerRunnable, 0);
        }
    }

Answer 2

If the user gets a phone call your app will call onPause then if they finish their phone call and play your game your activity will get onResume called.

in onPause save the system time, in onResume get the latest system time. Take these away from each other (in onResume) and you will have the time that the user was not in your app, you can then add this to your timer before you restart it.

You may also have to persist this time with onSaveInstanceState at other points.