AndroidのScrollViewはドラッグバウンス効果を実現
10105 ワード
public class BounceScrollView extends ScrollView {
private View inner;// View
private float y;// y
private Rect normal = new Rect();// ( ， .)
private boolean isCount = false;//
public BounceScrollView(Context context, AttributeSet attrs) {
super(context, attrs);
}
/***
* XML . ， . onFinishInflate
* ， ， .
*/
@Override
protected void onFinishInflate() {
if (getChildCount() > 0) {
inner = getChildAt(0);
}
}
/***
* touch
*/
@Override
public boolean onTouchEvent(MotionEvent ev) {
if (inner != null) {
commOnTouchEvent(ev);
}
return super.onTouchEvent(ev);
}
/***
*
*
* @param ev
*/
public void commOnTouchEvent(MotionEvent ev) {
int action = ev.getAction();
switch (action) {
case MotionEvent.ACTION_DOWN:
break;
case MotionEvent.ACTION_UP:
// .
if (isNeedAnimation()) {
animation();
isCount = false;
}
break;
/***
* ， y ， MotionEvent.ACTION_DOWN ，
* MyScrollView touch LIstView item . .
* ， 0. .
*/
case MotionEvent.ACTION_MOVE:
final float preY = y;// y
float nowY = ev.getY();// y
int deltaY = (int) (preY - nowY);//
if (!isCount) {
deltaY = 0; // 0.
}
y = nowY;
// ，
if (isNeedMove()) {
//
if (normal.isEmpty()) {
//
normal.set(inner.getLeft(), inner.getTop(),
inner.getRight(), inner.getBottom());
}
// Log.e("jj", " ：" + inner.getLeft() + "," + inner.getTop()
// + "," + inner.getRight() + "," + inner.getBottom());
//
inner.layout(inner.getLeft(), inner.getTop() - deltaY / 2,
inner.getRight(), inner.getBottom() - deltaY / 2);
}
isCount = true;
break;
default:
break;
}
}
/***
*
*/
public void animation() {
//
TranslateAnimation ta = new TranslateAnimation(0, 0, inner.getTop(), normal.top);
ta.setDuration(200);
inner.startAnimation(ta);
//
inner.layout(normal.left, normal.top, normal.right, normal.bottom);
// Log.e("jj", " ：" + normal.left + "," + normal.top + "," + normal.right
// + "," + normal.bottom);
normal.setEmpty();
}
//
public boolean isNeedAnimation() {
return !normal.isEmpty();
}
/***
* inner.getMeasuredHeight():
*
* getHeight()：
*
* @return
*/
public boolean isNeedMove() {
int offset = inner.getMeasuredHeight() - getHeight();
int scrollY = getScrollY();
// Log.e("jj", "scrolly=" + scrollY);
// 0 ，
if (scrollY == 0 || scrollY == offset) {
return true;
}
return false;
}
}