使用ViewDragHelper 实现吸边效果

来源：互联网发布：凡科建站域名绑定编辑：程序博客网时间：2024/04/27 20:38

由于项目需求需要按钮吸边，就自己动手写了下。对于通过手势拖拽我立马就想到了ViewDragHelper这个系统工具类。有了这个类的存在我们只需要处理松开手指的逻辑处理和边界控制就行了。
下面是实现代码

public class SuctionSideView extends RelativeLayout {    private final String TAG = "SuctionSideView";    private ViewDragHelper mDragHelper; // 拖拽控制    private View mSuctionView; // 要吸边的view    private Point mAutoBackOriginPos = new Point(); // 记录子view现在的位置    private boolean isInit = false;    /**     * 1 | 2     * -----     * 3 | 4     */    private int centerX;// 屏幕中心的x值    private int centerY;// 屏幕中心的y值 根据这两个属性建立直角坐标系    public SuctionSideView(@NonNull Context context) {        super(context,null);    }    public SuctionSideView(@NonNull Context context, @Nullable AttributeSet attrs) {        super(context, attrs);        init();        addListener();    }    /**     * 初始化布局     * @throws Exception     */    private void init() {    }    /**     * 监听事件注册     */    private void addListener() {        mDragHelper = ViewDragHelper.create(this, 1.0f, new ViewDragHelper.Callback() {            @Override            public boolean tryCaptureView(View child, int pointerId) {                return child == mSuctionView;            }            @Override            public int clampViewPositionHorizontal(View child, int left, int dx) {                final int leftBound = getPaddingLeft() + UIUtil.dp2px(10);                final int rightBound = getWidth() - child.getWidth() - leftBound  - UIUtil.dp2px(10);                final int newLeft = Math.min(Math.max(left, leftBound), rightBound);                return newLeft;            }            @Override            public int getViewHorizontalDragRange(View child) {                return getMeasuredWidth() - child.getMeasuredWidth();            }            @Override            public int clampViewPositionVertical(View child, int top, int dy) {                final int topBound = getPaddingTop()  + UIUtil.dp2px(10);                final int bottomBound = getHeight() - child.getHeight() - getPaddingBottom() - UIUtil.dp2px(10);                final int newTop = Math.min(Math.max(top,topBound),bottomBound);                return newTop;            }            @Override            public int getViewVerticalDragRange(View child) {                return getMeasuredHeight() - child.getMeasuredHeight();            }            @Override            public void onViewReleased(View releasedChild, float xvel, float yvel) {                if (releasedChild == mSuctionView) {                    if (releasedChild.getLeft() < centerX) { // 往左移动                        moveTo(UIUtil.dp2px(10) + getPaddingLeft(), releasedChild.getTop());                    } else { // 往右                        moveTo(getWidth() - UIUtil.dp2px(59) - getPaddingRight(), releasedChild.getTop());                    }//                    if (releasedChild.getLeft() < centerX && releasedChild.getTop() < centerY) { // 1象限//                        if (releasedChild.getLeft() < releasedChild.getTop()) { // 往左//                            moveTo(0, releasedChild.getTop());//                        } else { // 网上//                            moveTo(releasedChild.getLeft(), 0);//                        }//                    } else if (releasedChild.getLeft() > centerX && releasedChild.getTop() < centerY) { // 2象限//                        if (getWidth() - releasedChild.getLeft() - getWidth() < getTop() - releasedChild.getHeight()) { // 往右//                            moveTo(getWidth() - releasedChild.getWidth() - getPaddingRight(), releasedChild.getTop());//                        } else { // 往上//                            moveTo(releasedChild.getLeft(), 0);//                        }//                    } else if (releasedChild.getLeft() < centerX && releasedChild.getTop() > centerY) { // 3 象限//                        if (releasedChild.getLeft() < getHeight() - releasedChild.getTop() - releasedChild.getHeight()) { // 往左//                            moveTo(0, releasedChild.getTop());//                        } else { // 往下//                            moveTo(releasedChild.getLeft(), getHeight() - releasedChild.getHeight() - getPaddingBottom());//                        }//                    } else if (releasedChild.getLeft() > centerX && releasedChild.getTop() > centerY) { // 4象限//                        if (getWidth() - releasedChild.getLeft() - releasedChild.getWidth() < getHeight() - releasedChild.getTop() - releasedChild.getHeight()) { // 向右//                            moveTo(getWidth() - releasedChild.getWidth() - getPaddingRight(), releasedChild.getTop());//                        } else { // 往下//                            moveTo(releasedChild.getLeft(), getHeight() - releasedChild.getHeight() - getPaddingBottom());//                        }////                    }                    ViewCompat.postInvalidateOnAnimation(SuctionSideView.this);                }            }        });    }    private void moveTo(int xvel, int yvel) {        mAutoBackOriginPos.x = xvel;        mAutoBackOriginPos.y = yvel;        mDragHelper.smoothSlideViewTo(mSuctionView,xvel,yvel);    }    @Override    protected void onFinishInflate() {        super.onFinishInflate();        mSuctionView = getChildAt(0);        LogUtil.i(TAG,"onFinishInflate");    }    @Override    protected void onLayout(boolean changed, int l, int t, int r, int b) {        centerX = getWidth() / 2;        centerY = getHeight() / 2;        if (!isInit) {            mAutoBackOriginPos.x = getWidth() - UIUtil.dp2px(59);            mAutoBackOriginPos.y = getHeight() - UIUtil.dp2px(75);            isInit = true;            mSuctionView.layout(mAutoBackOriginPos.x,mAutoBackOriginPos.y,mAutoBackOriginPos.x + UIUtil.dp2px(49),mAutoBackOriginPos.y + UIUtil.dp2px(65));            LogUtil.i(TAG,"mAutoBackOriginPos.x:" + mAutoBackOriginPos.x + "mAutoBackOriginPos.y" + mAutoBackOriginPos.y);        }    }    @Override    public boolean onInterceptTouchEvent(MotionEvent ev) {        return mDragHelper.shouldInterceptTouchEvent(ev);    }    @Override    public boolean onTouchEvent(MotionEvent event) {        mDragHelper.processTouchEvent(event);        return false;    }    @Override    public void computeScroll() {        if (mDragHelper.continueSettling(true)) {            invalidate();        }    }}

这里面记录下吸边控件的初始位置。

clampViewPositionHorizontal与clampViewPositionVertical这是控制吸边控件的上下左右能够活动位置

由于我的项目中值需要左右吸边所以我在

onViewReleased 里只需要判断当前控件的left超过中心线了没

其中涉及到的数字为吸边控件距左距右和控件本身的尺寸，整个代码差不多100行是不是很简单吧。
使用也非常简单用自定义好的控件包裹住需要被吸边的控件

<cn.missfresh.home.widget.SuctionSideView        android:layout_width="match_parent"        android:layout_height="match_parent"        android:layout_below="@+id/title_bar">        <ImageView            android:id="@+id/view"            android:layout_width="49dp"            android:layout_height="65dp"            android:layout_gravity="right|bottom"            android:layout_marginBottom="10dp"            android:layout_marginRight="10dp"            android:scaleType="fitXY"            android:visibility="gone" />    </cn.missfresh.home.widget.SuctionSideView>

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