Repeat a task with a time delay?

Question

I have a variable in my code say it is \"status\".

I want to display some text in the application depending on this variable value. This has to be done with a speci

Answer 1

There are 3 ways to do it:

Use ScheduledThreadPoolExecutor

A bit of overkill since you don't need a pool of Thread

   //----------------------SCHEDULER-------------------------
    private final ScheduledThreadPoolExecutor executor_ =
            new ScheduledThreadPoolExecutor(1);
     ScheduledFuture schedulerFuture;
   public void  startScheduler() {
       schedulerFuture=  executor_.scheduleWithFixedDelay(new Runnable() {
            @Override
            public void run() {
                //DO YOUR THINGS
                pageIndexSwitcher.setVisibility(View.GONE);
            }
        }, 0L, 5*MILLI_SEC,  TimeUnit.MILLISECONDS);
    }


    public void  stopScheduler() {
        pageIndexSwitcher.setVisibility(View.VISIBLE);
        schedulerFuture.cancel(false);
        startScheduler();
    }

Use Timer Task

Old Android Style

    //----------------------TIMER  TASK-------------------------

    private Timer carousalTimer;
    private void startTimer() {
        carousalTimer = new Timer(); // At this line a new Thread will be created
        carousalTimer.scheduleAtFixedRate(new TimerTask() {
            @Override
            public void run() {
                //DO YOUR THINGS
                pageIndexSwitcher.setVisibility(INVISIBLE);
            }
        }, 0, 5 * MILLI_SEC); // delay
    }

    void stopTimer() {
        carousalTimer.cancel();
    }

Use Handler and Runnable

Modern Android Style

    //----------------------HANDLER-------------------------

    private Handler taskHandler = new android.os.Handler();

    private Runnable repeatativeTaskRunnable = new Runnable() {
        public void run() {
            //DO YOUR THINGS
        }
    };

   void startHandler() {
        taskHandler.postDelayed(repeatativeTaskRunnable, 5 * MILLI_SEC);
    }

    void stopHandler() {
        taskHandler.removeCallbacks(repeatativeTaskRunnable);
    }

Non-Leaky Handler with Activity / Context

Declare an inner Handler class which does not leak Memory in your Activity/Fragment class

/**
     * Instances of static inner classes do not hold an implicit
     * reference to their outer class.
     */
    private static class NonLeakyHandler extends Handler {
        private final WeakReference mActivity;

        public NonLeakyHandler(FlashActivity activity) {
            mActivity = new WeakReference(activity);
        }

        @Override
        public void handleMessage(Message msg) {
            FlashActivity activity = mActivity.get();
            if (activity != null) {
                // ...
            }
        }
    }

Declare a runnable which will perform your repetitive task in your Activity/Fragment class

   private Runnable repeatativeTaskRunnable = new Runnable() {
        public void run() {
            new Handler(getMainLooper()).post(new Runnable() {
                @Override
                public void run() {

         //DO YOUR THINGS
        }
    };

Initialize Handler object in your Activity/Fragment (here FlashActivity is my activity class)

//Task Handler
private Handler taskHandler = new NonLeakyHandler(FlashActivity.this);

To repeat a task after fix time interval

taskHandler.postDelayed(repeatativeTaskRunnable , DELAY_MILLIS);

To stop the repetition of task

taskHandler .removeCallbacks(repeatativeTaskRunnable );

UPDATE: In Kotlin:

    //update interval for widget
    override val UPDATE_INTERVAL = 1000L

    //Handler to repeat update
    private val updateWidgetHandler = Handler()

    //runnable to update widget
    private var updateWidgetRunnable: Runnable = Runnable {
        run {
            //Update UI
            updateWidget()
            // Re-run it after the update interval
            updateWidgetHandler.postDelayed(updateWidgetRunnable, UPDATE_INTERVAL)
        }

    }

 // SATART updating in foreground
 override fun onResume() {
        super.onResume()
        updateWidgetHandler.postDelayed(updateWidgetRunnable, UPDATE_INTERVAL)
    }


    // REMOVE callback if app in background
    override fun onPause() {
        super.onPause()
        updateWidgetHandler.removeCallbacks(updateWidgetRunnable);
    }