[java] Detecting a long press with Android

The solution by MSquare works only if you hold a specific pixel, but that's an unreasonable expectation for an end user unless they use a mouse (which they don't, they use fingers).

So I added a bit of a threshold for the distance between the DOWN and the UP action in case there was a MOVE action inbetween.

final Handler longPressHandler = new Handler();
Runnable longPressedRunnable = new Runnable() {
    public void run() {
        Log.e(TAG, "Long press detected in long press Handler!");
        isLongPressHandlerActivated = true;
    }
};

private boolean isLongPressHandlerActivated = false;

private boolean isActionMoveEventStored = false;
private float lastActionMoveEventBeforeUpX;
private float lastActionMoveEventBeforeUpY;

@Override
public boolean dispatchTouchEvent(MotionEvent event) {
    if(event.getAction() == MotionEvent.ACTION_DOWN) {
        longPressHandler.postDelayed(longPressedRunnable, 1000);
    }
    if(event.getAction() == MotionEvent.ACTION_MOVE || event.getAction() == MotionEvent.ACTION_HOVER_MOVE) {
        if(!isActionMoveEventStored) {
            isActionMoveEventStored = true;
            lastActionMoveEventBeforeUpX = event.getX();
            lastActionMoveEventBeforeUpY = event.getY();
        } else {
            float currentX = event.getX();
            float currentY = event.getY();
            float firstX = lastActionMoveEventBeforeUpX;
            float firstY = lastActionMoveEventBeforeUpY;
            double distance = Math.sqrt(
                    (currentY - firstY) * (currentY - firstY) + ((currentX - firstX) * (currentX - firstX)));
            if(distance > 20) {
                longPressHandler.removeCallbacks(longPressedRunnable);
            }
        }
    }
    if(event.getAction() == MotionEvent.ACTION_UP) {
        isActionMoveEventStored = false;
        longPressHandler.removeCallbacks(longPressedRunnable);
        if(isLongPressHandlerActivated) {
            Log.d(TAG, "Long Press detected; halting propagation of motion event");
            isLongPressHandlerActivated = false;
            return false;
        }
    }
    return super.dispatchTouchEvent(event);
}