How to pause / sleep thread or process in Android?


Question

I want to make a pause between two lines of code, Let me explain a bit:

-> the user clicks a button (a card in fact) and I show it by changing the background of this button:

thisbutton.setBackgroundResource(R.drawable.icon);

-> after let's say 1 second, I need to go back to the previous state of the button by changing back its background:

thisbutton.setBackgroundResource(R.drawable.defaultcard);

-> I've tried to pause the thread between these two lines of code with:

try {
    Thread.sleep(1000);
} catch (InterruptedException e) {
    // TODO Auto-generated catch block
    e.printStackTrace();
}

However, this does not work. Maybe it's the process and not the Thread that I need to pause?

I've also tried (but it doesn't work):

new Reminder(5);

With this:

public class Reminder {

Timer timer;

        public Reminder(int seconds) {
            timer = new Timer();
            timer.schedule(new RemindTask(), seconds*1000);
        }

        class RemindTask extends TimerTask {
            public void run() {
                System.out.format("Time's up!%n");
                timer.cancel(); //Terminate the timer thread
            }
        }  
    }

How can I pause/sleep the thread or process?

1
280
1/18/2015 3:30:12 PM

Accepted Answer

One solution to this problem is to use the Handler.postDelayed() method. Some Google training materials suggest the same solution.

@Override
public void onClick(View v) {
    my_button.setBackgroundResource(R.drawable.icon);

    Handler handler = new Handler(); 
    handler.postDelayed(new Runnable() {
         @Override 
         public void run() { 
              my_button.setBackgroundResource(R.drawable.defaultcard); 
         } 
    }, 2000); 
}

However, some have pointed out that the solution above causes a memory leak because it uses a non-static inner and anonymous class which implicitly holds a reference to its outer class, the activity. This is a problem when the activity context is garbage collected.

A more complex solution that avoids the memory leak subclasses the Handler and Runnable with static inner classes inside the activity since static inner classes do not hold an implicit reference to their outer class:

private static class MyHandler extends Handler {}
private final MyHandler mHandler = new MyHandler();

public static class MyRunnable implements Runnable {
    private final WeakReference<Activity> mActivity;

    public MyRunnable(Activity activity) {
        mActivity = new WeakReference<>(activity);
    }

    @Override
    public void run() {
        Activity activity = mActivity.get();
        if (activity != null) {
            Button btn = (Button) activity.findViewById(R.id.button);
            btn.setBackgroundResource(R.drawable.defaultcard);
        }
    }
}

private MyRunnable mRunnable = new MyRunnable(this);

public void onClick(View view) {
    my_button.setBackgroundResource(R.drawable.icon);

    // Execute the Runnable in 2 seconds
    mHandler.postDelayed(mRunnable, 2000);
}

Note that the Runnable uses a WeakReference to the Activity, which is necessary in a static class that needs access to the UI.

440
5/10/2018 8:06:14 PM

You can try this one it is short

SystemClock.sleep(7000);

WARNING: Never, ever, do this on a UI thread.

Use this to sleep eg. background thread.


Full solution for your problem will be: This is available API 1

findViewById(R.id.button).setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(final View button) {
                button.setBackgroundResource(R.drawable.avatar_dead);
                final long changeTime = 1000L;
                button.postDelayed(new Runnable() {
                    @Override
                    public void run() {
                        button.setBackgroundResource(R.drawable.avatar_small);
                    }
                }, changeTime);
            }
        });

Without creating tmp Handler. Also this solution is better than @tronman because we do not retain view by Handler. Also we don't have problem with Handler created at bad thread ;)

Documentation

public static void sleep (long ms)

Added in API level 1

Waits a given number of milliseconds (of uptimeMillis) before returning. Similar to sleep(long), but does not throw InterruptedException; interrupt() events are deferred until the next interruptible operation. Does not return until at least the specified number of milliseconds has elapsed.

Parameters

ms to sleep before returning, in milliseconds of uptime.

Code for postDelayed from View class:

/**
 * <p>Causes the Runnable to be added to the message queue, to be run
 * after the specified amount of time elapses.
 * The runnable will be run on the user interface thread.</p>
 *
 * @param action The Runnable that will be executed.
 * @param delayMillis The delay (in milliseconds) until the Runnable
 *        will be executed.
 *
 * @return true if the Runnable was successfully placed in to the
 *         message queue.  Returns false on failure, usually because the
 *         looper processing the message queue is exiting.  Note that a
 *         result of true does not mean the Runnable will be processed --
 *         if the looper is quit before the delivery time of the message
 *         occurs then the message will be dropped.
 *
 * @see #post
 * @see #removeCallbacks
 */
public boolean postDelayed(Runnable action, long delayMillis) {
    final AttachInfo attachInfo = mAttachInfo;
    if (attachInfo != null) {
        return attachInfo.mHandler.postDelayed(action, delayMillis);
    }
    // Assume that post will succeed later
    ViewRootImpl.getRunQueue().postDelayed(action, delayMillis);
    return true;
}

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