MotionEvent.ACTION_UP not called

Also note that under certain circumstances (eg. screen rotations) the gesture may be cancelled, in which case a MotionEvent.ACTION_UP will NOT be sent. Instead a MotionEvent.ACTION_CANCEL is sent instead. Therefore a normal action switch statement should look something like this:

switch (event.getActionMasked()) {
    case MotionEvent.ACTION_DOWN:
        // check if we want to handle touch events, return true
        // else don't handle further touch events, return false
    break;

    // ... handle other cases

    case MotionEvent.ACTION_UP:
    case MotionEvent.ACTION_CANCEL:
        // finish handling touch events
        // note that these methods won't be called if 'false' was returned
        // from any previous events related to the gesture
    break;
}

You should return true; in case MotionEvent.ACTION_DOWN:, so the MotionEvent.ACTION_UP will be handled.

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As explained on View.OnTouchListener:

Returns:

True if the listener has consumed the event, false otherwise.

MotionEvent.ACTION_UP Won't get called until the MotionEvent.ACTION_DOWN occurred, a logical explanation for this is that it's impossible for an ACTION_UP to occur if an ACTION_DOWN never occurred before it.

This logic enables the developer to block further events after ACTION_DOWN.