How to customize ScrollView to realize damping springback by Android
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The solution is as follows:
ScrollView is required to have one and only one child View inside. When the ScrollView slides to the boundary, let the sub-View translate with the fingers according to certain rules in the ScrollView to simulate the stretching effect. When the finger is released, the sub-View is restored to its pre-stretch position to simulate the springback effect.
The complete code is as follows. For detailed principles, please see the notes.
Public class StretchScrollView extends NestedScrollView {/ / subView private View innerView; / / the y coordinate of the last gesture event private float mLastY; / / record the normal position of the subView private Rect normal = new Rect (); public StretchScrollView (Context context, AttributeSet attrs) {super (context, attrs);} @ Override protected void onFinishInflate () {initView (); super.onFinishInflate () } / * get the sublayout of ScrollView * / private void initView () {/ / remove the shadow effect setOverScrollMode (OVER_SCROLL_NEVER) when the original ScrollView scrolls to the boundary; if (getChildAt (0)! = null) {innerView = getChildAt (0) } @ Override public boolean onTouchEvent (MotionEvent ev) {switch (ev.getAction ()) {case MotionEvent.ACTION_UP: / / release the finger to recover if (! normal.isEmpty ()) {planAnimation (); normal.setEmpty (); mLastY = 0 } break; case MotionEvent.ACTION_MOVE: float currentY = ev.getY (); / / sliding distance int distanceY = (int) (mLastY-currentY) / / handle the scrolling event of the Y axis. When you scroll to the top or bottom, you need to move the layout / / this event will also be triggered when the finger touches the screen. When the value of mLastY is still 0, a large movement will be triggered immediately. Filter out this situation here if (isNeedTranslate () & & mLastY! = 0) {if (normal.isEmpty ()) {/ / save the normal layout location normal.set (innerView.getLeft (), innerView.getTop (), innerView.getRight (), innerView.getBottom () } / / move the layout to prevent distance / 2 from translating too fast innerView.layout (innerView.getLeft (), innerView.getTop ()-distanceY / 2, innerView.getRight (), innerView.getBottom ()-distanceY / 2);} mLastY = currentY Break;} return super.onTouchEvent (ev);} / * * retractive animation * / public void planAnimation () {/ / enable mobile animation TranslateAnimation animation = new TranslateAnimation (0,0, innerView.getTop (), normal.top); animation.setDuration (200C); innerView.startAnimation (animation) / / the motion tween does not really modify the position of innerView. Here you need to set the innerView to return to its normal layout position innerView.layout (normal.left, normal.top, normal.right, normal.bottom);} / * whether Y mobile layout is required * / public boolean isNeedTranslate () {int offset = innerView.getMeasuredHeight ()-getHeight (); int scrollY = getScrollY () / / Top or bottom return scrollY = = 0 | | scrollY = = offset;}} above is all the content of the article "how to customize ScrollView to achieve damping springback by Android". Thank you for reading! I believe you will gain a lot after reading this article. The editor will update different knowledge for you every day. If you want to learn more knowledge, please pay attention to the industry information channel.
