Advanced event handling

We've seen how to process onTouchEvent(), but we can also detect some gestures or more complex interactions. Android provides us with the GestureDetector to help us detect some gestures. There is even a GestureDetectorCompat on the support library to provide this support to older versions of Android.

For more information on the GestureDetector, please check the Android documentation.

Detecting gestures

Let's change the code we've been building to use GestureDetector. We'll also use a Scroller implementation to scroll smoothly between values. We can modify the constructor to create the Scroller object and the GestureDetector with an implementation of a GestureDetector.OnGestureListener:

private GestureDetector gestureListener; 
private Scroller angleScroller; 
 
public CircularActivityIndicator(Context context, AttributeSet attributeSet) { 
    super(context, attributeSet); 
 
    ... 
     
    selectedAngle = 280; 
    pressed = false; 
 
    angleScroller = new Scroller...