ScrollView的反弹效果

来源：互联网发布：银行业发展前景知乎编辑：程序博客网时间：2024/04/29 10:13
public class ReboundScrollview extends ScrollView {    // 拖动的距离 size = 4 的意思 只允许拖动屏幕的1/4    private static final int size = 3;    private View inner;    private float y;    private Rect normal = new Rect();    public ReboundScrollview(Context context) {        super(context);    }    public ReboundScrollview(Context context, AttributeSet attrs) {        super(context, attrs);    }    public ReboundScrollview(Context context, AttributeSet attrs, int defStyle) {        super(context, attrs, defStyle);    }    @Override    protected void onFinishInflate() {        if (getChildCount() > 0) {            inner = getChildAt(0);        }    }    @Override    public void requestChildFocus(View child, View focused) {        if (focused instanceof WebView || focused instanceof ListView) {            return;        }        super.requestChildFocus(child, focused);    }    @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()) {                    // Log.v("mlguitar", "will up and animation");                    animation();                }                break;            case MotionEvent.ACTION_MOVE:                final float preY = y;                float nowY = ev.getY();                /**                 * size=4 表示 拖动的距离为屏幕的高度的1/4                 */                int deltaY = (int) (preY - nowY) / size;                // 滚动                // scrollBy(0, deltaY);                y = nowY;                // 当滚动到最上或者最下时就不会再滚动，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());                        return;                    }                    int yy = inner.getTop() - deltaY;                    // 移动布局                    inner.layout(inner.getLeft(), yy, inner.getRight(),                            inner.getBottom() - deltaY);                }                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;    }    private OnScrollViewListener scrollViewListener;    public void setOnScrollListener(OnScrollViewListener onScrollListener) {        this.scrollViewListener = onScrollListener;    }    public interface OnScrollViewListener {        void onScrollChanged(int x, int y, int oldx, int oldy);    }    @Override    protected void onScrollChanged(int x, int y, int oldx, int oldy) {        if (scrollViewListener != null) {            scrollViewListener.onScrollChanged(x, y, oldx, oldy);        }        super.onScrollChanged(x, y, oldx, oldy);    }}
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