How to implement Swipe action in Android

출처(source) : http://www.codeshogun.com/blog/2009/04/16/how-to-implement-swipe-action-in-android/

To implement swipe action in Android, such as the one used in iPhone homescreen unlock, actually Android SDK provides native support for gestures. Swipe is actually called Fling ^_^

You will need to extend SimpleOnGestureListener to implement your own handling on swipe/fling action:

class MyGestureDetector extends SimpleOnGestureListener {
@Override
public boolean onFling(MotionEvent e1, MotionEvent e2, float velocityX, float velocityY) {
}


To determine if it’s a valid swipe, you will need to make sure the fling falls into an almost straight path, with at least certain length of touch duration, so it’s a continuous touch, and with certain velocity of course.

So let’s define some constants:

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;


The max off path is to make sure the fling still falls within a somewhat straight path.

If onFling() method, you can do this:

if(e1.getX() - e2.getX() > SWIPE_MIN_DISTANCE && Math.abs(velocityX) > SWIPE_THRESHOLD_VELOCITY) {
viewFlipper.setInAnimation(slideLeftIn);
viewFlipper.setOutAnimation(slideLeftOut);
viewFlipper.showNext();
} else if (e2.getX() - e1.getX() > SWIPE_MIN_DISTANCE && Math.abs(velocityX) > SWIPE_THRESHOLD_VELOCITY) {
viewFlipper.setInAnimation(slideRightIn);
viewFlipper.setOutAnimation(slideRightOut);
viewFlipper.showPrevious();
}


The viewFlipper is used to show how fling/swipe make the view animation/transition from one to the other.

At last, you need to make sure in your activity, you catch the gesture event by overriding onTouch() method:

@Override
public boolean onTouchEvent(MotionEvent event) {
if (gestureDetector.onTouchEvent(event))
return true;
else
return false;
}


Here’s a screenshot of the view in transition:

Android Swipe View Flipper in Action

The sample source is attached here.