Android : How to implement longpress manually in touch event?

Question

Short version: I want a way to start a time-based counter on an onTouchEvent, and test to see if a certain amount of time has passed before responding, as a manual LongTouch detection.

Explanation: I have a custom imageView that slides in/out of screen on two-fingered flings. I want to add drag events to it, but these need to be quicker than a longpress. I can delay the drag event by using a counter that updates once per onTouchEvent and only triggers the drag on, say, 10 counts, but the counter only updates on touch events and the finger must be moving.

How can I create a time-based counter, an Activity level field that's incremented 60 times a second or somesuch?

Answer 1

I'm not sure from you question, but it seems that you're trying to implement a catch long click event in your onTouchListener except you need to perform some kind of logic before the ACTION_UP event happens? If so, that's the same exact problem I was having. I also tried using System.nanoTime() but I found a less tricky method. You CAN use a timer, you just have to schedule it on the first ACTION_DOWN event and cancel it when anything adverse happens (like an ACTION_UP which means it's wasn't a long press but just a click, or an ACTION_MOVE with a displacement over a certain threshold). Something like the following:

layout.seyOnTouchListener(new OnTouchListener(){
    private Timer longpressTimer; //won't depend on a motion event to fire
    private final int longpressTimeDownBegin = 500; //0.5 s
    private Point previousPoint;

    switch(event.getAction()){

    case MotionEvent.ACTION_DOWN:{
        longPressTimer = new Timer();
        longpressTimer.schedule(new TimerTask(){
            //whatever happens on a longpress
        }, longpressTimeDownBegin);
        return true; //the parent was also handling long clicks
    }
    case MotionEvent.ACTION_MOVE:{
        Point currentPoint = new Point((int)event.getX(), (int)event.getY());

        if(previousPoint == null){
            previousPoint = currentPoint;
        }
        int dx = Math.abs(currentPoint.x - previousPoint.x);
        int dy = Math.abs(currentPoint.y - previousPoint.y);
        int s = (int) Math.sqrt(dx*dx + dy*dy);
        boolean isActuallyMoving = s >= minDisToMove; //we're moving

        if(isActuallyMoving){ //only restart timer over if we're actually moving (threshold needed because everyone's finger shakes a little)
            cancelLongPress();
            return false; //didn't trigger long press (will be treated as scroll)
        }
        else{ //finger shaking a little, so continue to wait for possible long press
            return true; //still waiting for potential long press
        }
    }
    default:{
        cancelLongPress();
        return false;
    }
    }
}