自定义ScrollView实现下拉反弹的效果(有点类似于下拉刷新)。

一个简单的下拉反弹效果。(网上代码整理)
通过自定义ScrollView实现。

public class BounceScrollView extends ScrollView {

    private View inner;

    private float y;

    private Rect normal = new Rect();

    private boolean isCount = false;

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


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

    public boolean onTouchEvent(MotionEvent ev) {
        if (inner != null) {
            commOnTouchEvent(ev);
        }
        return super.onTouchEvent(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;
        case MotionEvent.ACTION_MOVE:
            final float preY = y;
            float nowY = ev.getY();
            int deltaY = (int) (preY - nowY);
            if (!isCount) {
                deltaY = 0;
            }

            y = nowY;
            if (isNeedMove()) {
                if (normal.isEmpty()) {
                    normal.set(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(1000);
        inner.startAnimation(ta);

        inner.layout(normal.left, normal.top, normal.right, normal.bottom);
        normal.setEmpty();
    }


    public boolean isNeedAnimation(){
        return !normal.isEmpty();
    }


    public boolean isNeedMove(){
        int offset = inner.getMeasuredHeight() - getHeight();
        int scrollY = getScrollY();
        if (scrollY == 0 || scrollY == offset ) {
            return true;
        }
        return false;
    }

}

效果类似于listview下拉刷新。这里不配图。