Detecting up-down, left-right swipe on Android with greater accuracy.

28 Apr 2014

This probably is the simplest way to detect the exact swipe direction on Android. We split the screen into four quadrants and then use the MotionEvents to calculate the angle of swipe. The code is pretty self explanatory.

class SwipeGestureDetector extends SimpleOnGestureListener {

    @Override 
    public boolean onFling(MotionEvent e1, MotionEvent e2, 
        float velocityX, float velocityY) {

        switch (getSlope(e1.getX(), e1.getY(), e2.getX(), e2.getY())) {
        case 1:
            Log.d(LOGTAG, "top");
            return true;
        case 2:
            Log.d(LOGTAG, "left");
            return true;
        case 3:
            Log.d(LOGTAG, "down");
            return true;
        case 4:
            Log.d(LOGTAG, "right");
            return true;
        }
        return false;
    }

    private int getSlope(float x1, float y1, float x2, float y2) {
        Double angle = Math.toDegrees(Math.atan2(y1 - y2, x2 - x1));
        if (angle > 45 && angle <= 135)
        // top
        return 1;
        if (angle >= 135 && angle < 180 || angle < -135 && angle > -180)
        // left
        return 2;
        if (angle < -45 && angle>= -135)
        // down
        return 3;
        if (angle > -45 && angle <= 45)
        // right
        return 4;
        return 0;
    }

To check out how to use this SwipeGestureDetector class with the relevant view, check out this post.