Android: How to detect double-tap?

You can use the GestureDetector. See the following code:

public class MyView extends View {

    GestureDetector gestureDetector;

    public MyView(Context context, AttributeSet attrs) {
        super(context, attrs);
                // creating new gesture detector
        gestureDetector = new GestureDetector(context, new GestureListener());
    }

    // skipping measure calculation and drawing

        // delegate the event to the gesture detector
    @Override
    public boolean onTouchEvent(MotionEvent e) {
        return gestureDetector.onTouchEvent(e);
    }


    private class GestureListener extends GestureDetector.SimpleOnGestureListener {

        @Override
        public boolean onDown(MotionEvent e) {
            return true;
        }
        // event when double tap occurs
        @Override
        public boolean onDoubleTap(MotionEvent e) {
            float x = e.getX();
            float y = e.getY();

            Log.d("Double Tap", "Tapped at: (" + x + "," + y + ")");

            return true;
        }
    }
}

You can override other methods of the listener to get single taps, flinges and so on.

combining "Bughi" "DoubleClickListner" and "Jayant Arora" Timer in one contained class:

public abstract class DoubleClickListener implements OnClickListener {

    private Timer timer = null;  //at class level;
    private int DELAY   = 400;

    private static final long DOUBLE_CLICK_TIME_DELTA = 300;//milliseconds

    long lastClickTime = 0;

    @Override
    public void onClick(View v) {
        long clickTime = System.currentTimeMillis();
        if (clickTime - lastClickTime < DOUBLE_CLICK_TIME_DELTA){
            processDoubleClickEvent(v);
        } else {
            processSingleClickEvent(v);
        }
        lastClickTime = clickTime;
    }



    public void processSingleClickEvent(final View v){

        final Handler handler=new Handler();
        final Runnable mRunnable=new Runnable(){
            public void run(){
                onSingleClick(v); //Do what ever u want on single click

            }
        };

        TimerTask timertask=new TimerTask(){
            @Override
            public void run(){
                handler.post(mRunnable);
            }
        };
        timer=new Timer();
        timer.schedule(timertask,DELAY);

    }

    public void processDoubleClickEvent(View v){
        if(timer!=null)
        {
            timer.cancel(); //Cancels Running Tasks or Waiting Tasks.
            timer.purge();  //Frees Memory by erasing cancelled Tasks.
        }
        onDoubleClick(v);//Do what ever u want on Double Click
    }

    public abstract void onSingleClick(View v);

    public abstract void onDoubleClick(View v);
}

and can be called as :

view.setOnClickListener(new DoubleClickListener() {

            @Override
            public void onSingleClick(View v) {

            }

            @Override
            public void onDoubleClick(View v) {

            }
        });

As a lightweight alternative to GestureDetector you can use this class

public abstract class DoubleClickListener implements OnClickListener {

    private static final long DOUBLE_CLICK_TIME_DELTA = 300;//milliseconds

    long lastClickTime = 0;

    @Override
    public void onClick(View v) {
        long clickTime = System.currentTimeMillis();
        if (clickTime - lastClickTime < DOUBLE_CLICK_TIME_DELTA){
            onDoubleClick(v);
        } else {
            onSingleClick(v);
        }
        lastClickTime = clickTime;
    }

    public abstract void onSingleClick(View v);
    public abstract void onDoubleClick(View v);
}

Example:

    view.setOnClickListener(new DoubleClickListener() {

        @Override
        public void onSingleClick(View v) {

        }

        @Override
        public void onDoubleClick(View v) {

        }
    });

Why aren't you using a Long Press? Or are you using that already for something else? The advantages of a Long Press over a Double Touch:

• Long Press is a recommeded interaction in the UI Guidelines, Double Touch is not.
• It's what users expect; a user might not find a Double Touch action as they won't go looking for it
• It's already handled in the API.
• Implementing a Double Touch will affect handling of Single Touches, because you'll have to wait to see if every Single Touch turns into a Double Touch before you can process it.