// Abort any active scroll animations and invalidate.
mScroller.forceFinished(true);
// There is also a compatibility version:
// ViewCompat.postInvalidateOnAnimation
postInvalidateOnAnimation();
return true;
}
@Override
public boolean onScroll(MotionEvent e1, MotionEvent e2,
float distanceX, float distanceY) {
// You don't use a scroller in onScroll because you don't need to animate
// a scroll. The scroll occurs instantly in response to touch feedback.
return false;
}
@Override
public boolean onFling(MotionEvent e1, MotionEvent e2,
float velocityX, float velocityY) {
// Before flinging, abort the current animation.
mScroller.forceFinished(true);
// Begin the scroll animation
mScroller.fling(
// Current scroll position
startX,
startY,
// Velocities, negated for natural touch response
(int) -velocityX,
(int) -velocityY,
// Minimum and maximum scroll positions. The minimum scroll
// position is generally zero and the maximum scroll position
// is generally the content size less the screen size. So if the
// content width is 1000 pixels and the screen width is 200
// pixels, the maximum scroll offset should be 800 pixels.
minX, maxX,
minY, maxY,
// The maximum overscroll bounds. This is useful when using
// the EdgeEffect class to draw overscroll "glow" overlays.
mContentRect.width() / 2,
mContentRect.height() / 2);
// Invalidate to trigger computeScroll()
postInvalidateOnAnimation();
return true;
}
};
@Override
public void computeScroll() {
super.computeScroll();
// Compute the current scroll offsets. If this returns true, then the
// scroll has not yet finished.
if (mScroller.computeScrollOffset()) {
int currX = mScroller.getCurrX();
int currY = mScroller.getCurrY();
// Actually render the scrolled viewport, or actually scroll the
// view using View.scrollTo.
// If currX or currY are outside the bounds, render the overscroll
// glow using EdgeEffect.
} else {
// The scroll has finished.
}
}</pre>
<p>For another example of scroller usage, see the <a href="http://github.com/android/platform_frameworks_support/blob/master/v4/java/android/support/v4/view/ViewPager.java">source code</a> for the
