Pause the timer and then continue it

Question

Refer to the code that @Yuri posted from here. How to stop a timer after certain number of times . If I wanted to stop it because of some condition and then restart it again. How would I go about doing it?

    private final static int DELAY = 10000;
    private final Handler handler = new Handler();
    private final Timer timer = new Timer();
    private final TimerTask task = new TimerTask() {
        private int counter = 0;
        public void run() {
            handler.post(new Runnable() {
                public void run() {
                    Toast.makeText(MainActivity.this, "test", Toast.LENGTH_SHORT).show();
                }
            });
            if(++counter == 4) {
                timer.cancel();
            }

    //do some stuff in my app
   //restart the timer again

        }
    };

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        timer.schedule(task, DELAY, DELAY);

    }

Here's what I've tried , but it keeps crashing on me.

    final int DELAY = 10000;
        Timer timer;
        MyTask task;
        startManager Scanner;
        Handler handler;



        public class MyTask extends TimerTask {

            @Override
            public void run() {
                handler.post(new Runnable() {
                    public void run() {
                        //do Stuff here
                        }
        });
    }
        public class startManager {

            public startManager() {
                handler = new Handler();
                timer = new Timer();
            }

            public void start() {

                timer.schedule(task, 0, DELAY);
            }

            public void cancel() {

                timer.cancel();
                timer.purge();

            }
        }

    }

 @Override
        public void onCreate(Bundle savedInstanceState) {
            super.onCreate(savedInstanceState);
            setContentView(R.layout.activity_main);

Scanner = new startManager();
//do some stuff
 if (...)
Scanner.cancel()
//restart the timer and its task
Scanner=new startManager();
        }

Answer 1

FIgured it out, it was because I didn't initialize the task in startManager()

Answer 2

If you have already canceled one timer, you can't re-start it, you'll have to create a new one.

See this answer, it contains a video and the source code how I did something similar.

Basically there are two method: pause and resume

In pause:

public void pause() {
    this.timer.cancel();
}

In resume:

public void resume() {
    this.timer = new Timer();
    this.timer.schedule( aTask, 0, 1000 );
}

That makes the perception of pause/resume.

If your timers perform different actions based on the state of the application you may consider use the StatePattern

Fist define a abstract state:

abstract class TaskState  {
    public void run();
    public TaskState next();
}

And provide as many states as you like. The key is that one state leads you to another.

class InitialState extends TaskState {
    public void run() {
        System.out.println( "starting...");
    }
    public TaskState next() {
         return new FinalState();
    }
 }
 class FinalState extends TaskState  {
     public void run() {
         System.out.println("Finishing...");
     }
     public TaskState next(){
         return new InitialState();
    }
 }

And then you change the state in your timer.

Timer timer = new Timer();
TaskState state = new InitialState();

timer.schedule( new TimerTask() {
     public void run() {
          this.state.run();
          if( shouldChangeState() ) {
              this.state = this.state.next();
           }
     }
 }, 0, 1000 );

Finally, if what you need is to perform the same thing, but at different rates, you may consider using the TimingFramework. It is a bit more complex but let's you do cool animations, by allowing the painting of certain component take place at different rates ( instead of being linear )

Answer 3

There appears to be no way to do this: http://docs.oracle.com/javaee/6/api/javax/ejb/Timer.html

You could likely cancel the timer, then create a new one.