Android进阶篇-自定义ScrollView反弹效果

public class autoScrollView extends ScrollView {
private View inner;
private float y;
private Rect normal = new Rect();

public autoScrollView(Context context) {
super(context);
// TODO Auto-generated constructor stub
}

public autoScrollView(Context context, AttributeSet attrs) {
super(context, attrs);
}

public autoScrollView(Context context, AttributeSet attrs, int defStyle) {
super(context, attrs, defStyle);
// TODO Auto-generated constructor stub
}

@Override
protected void onFinishInflate() {
if (getChildCount() > 0) {
inner = getChildAt(0);
}
}

@Override
public boolean onTouchEvent(MotionEvent ev) {
if (inner == null) {
return super.onTouchEvent(ev);
} else {
commOnTouchEvent(ev);
}

return super.onTouchEvent(ev);
}

public void commOnTouchEvent(MotionEvent ev) {
int action = ev.getAction();
switch (action) {
case MotionEvent.ACTION_DOWN:
y = ev.getY();
break;
case MotionEvent.ACTION_UP:
if (isNeedAnimation()) {
animation();
}
break;
case MotionEvent.ACTION_MOVE:
final float preX = y;
float nowY = ev.getY();
int deltaY = (int) (preX - nowY);
// 滚动
scrollBy(0, deltaY);

y = nowY;
// 当滚动到最左或者最右时就不会再滚动，这时移动布局
if (isNeedMove()) {
if (normal.isEmpty()) {
// 保存正常的布局位置
normal.set(inner.getLeft(), inner.getTop(), inner.getRight(), inner.getBottom());
}
// 移动布局
inner.layout(inner.getLeft(), inner.getTop()-deltaY/2, inner.getRight(), inner.getBottom()-deltaY/2);
}
break;

default:
break;
}
}

// 开启动画移动
public void animation() {
// 开启移动动画
TranslateAnimation ta = new TranslateAnimation(0, 0, inner.getTop(), normal.top);
ta.setDuration(200);
inner.startAnimation(ta);
// 设置回到正常的布局位置
inner.layout(normal.left, normal.top, normal.right, normal.bottom);
normal.setEmpty();
}

// 是否需要开启动画
public boolean isNeedAnimation() {
return !normal.isEmpty();
}

// 是否需要移动布局
public boolean isNeedMove() {
int offset = inner.getMeasuredHeight() - getHeight();
int scrollY = getScrollY();
if (scrollY == 0 || scrollY == offset) {
return true;
}
return false;
}
}