kentcdodds kentcdodds - 2 months ago 17
Android Question

How to detect swipe direction between left/right and up/down

My Question: How do I detect when a user moves their finger up/down vs left/right (and how do I know which direction of those groups their finger moved)?

My Situation: I want to change the brightness of my app when they move their finger up and down (up = brighter, down = darker), and I want to switch between activities and/or views based on their left/right swipe.

Answer

You simply have to extend SimpleOnGestureListener class,

Declare this in your class,

    private static final int SWIPE_MIN_DISTANCE = 120;
private static final int SWIPE_MAX_OFF_PATH = 250;
private static final int SWIPE_THRESHOLD_VELOCITY = 200;

As an example for horizontal swipe you can see the below code,

 class MyGestureDetector extends SimpleOnGestureListener {
    @Override
    public boolean onFling(MotionEvent e1, MotionEvent e2, float velocityX,
            float velocityY) {
        try {
            if (Math.abs(e1.getY() - e2.getY()) > SWIPE_MAX_OFF_PATH){
                return false;
            }
            // right to left swipe
            if (e1.getX() - e2.getX() > SWIPE_MIN_DISTANCE
                    && Math.abs(velocityX) > SWIPE_THRESHOLD_VELOCITY) {
                onLeftSwipe();
            } 
            // left to right swipe
            else if (e2.getX() - e1.getX() > SWIPE_MIN_DISTANCE
                    && Math.abs(velocityX) > SWIPE_THRESHOLD_VELOCITY) {
                onRightSwipe();
            }
        } catch (Exception e) {

        }
        return false;
      }
   }

You can do this similarly for vertical swipe purpose.

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