滑动返回-方式2

SwipeBackLayout

项目地址：Alex-Cin/SwipeBackLayout

之前写过一个 在Activity 里面，利用dispatchTouchEvent方法，实现了滑动返回，今天写一个自定义控件，并借助ViewDragHelper实现的滑动返回

• 先看效果图

001.png

002.gif

核心代码量不多，注释很详细了

package github.alex.swipebacklayout;/** * 作者：alex * 时间：2016/8/12 11:49 *  */public class SwipeBackLayout extends FrameLayout {    private ViewDragHelper viewDragHelper;    private View rootView;    private Activity activity;    /**     * 手机屏幕的 宽度     */    private int screenWidth;    /**     * 是否 允许 执行 滑动返回操作     */    private boolean canSwipeBack;    private OnSwipeBackListener onSwipeBackListener;    public SwipeBackLayout(Context context) {        super(context);        initView();    }    public SwipeBackLayout(Context context, AttributeSet attrs) {        super(context, attrs);        initView();    }    private void initView() {        screenWidth = getScreenWidth();        canSwipeBack = true;        ViewDragHelperCallback dragHelperCallback = new ViewDragHelperCallback();        viewDragHelper = ViewDragHelper.create(this, 1.0F, dragHelperCallback);        /*跟踪左边界拖动*/        viewDragHelper.setEdgeTrackingEnabled(ViewDragHelper.EDGE_LEFT);    }    /**     * 绑定 Activity     *     * @param activity 容器 Activity     */    public SwipeBackLayout attachActivity(Activity activity) {        this.activity = activity;        ViewGroup decor = (ViewGroup) activity.getWindow().getDecorView();        View content = decor.getChildAt(0);        decor.removeView(content);        rootView = content;        addView(content);        decor.addView(this);        return this;    }    /**     * 是否 允许 执行 滑动返回操作     */    public SwipeBackLayout canSwipeBack(boolean canSwipeBack) {        this.canSwipeBack = canSwipeBack;        return this;    }    public SwipeBackLayout onSwipeBackListener(OnSwipeBackListener onSwipeBackListener) {        this.onSwipeBackListener = onSwipeBackListener;        return this;    }    @Override    public boolean onInterceptTouchEvent(MotionEvent ev) {        if (!canSwipeBack) {            return false;        }        /*拦截代理*/        return viewDragHelper.shouldInterceptTouchEvent(ev);    }    /**     * 这里必须 返回 true，否则 viewDragHelper 将会失效     */    @Override    public boolean onTouchEvent(MotionEvent event) {        if (!canSwipeBack) {            return false;        }        LogUtil.e("进来了");        /*Touch Event 代理*/        viewDragHelper.processTouchEvent(event);        //return super.onTouchEvent(event);        return true;    }    /*view 刚初始化的时候就会被调用一次*/    @Override    public void computeScroll() {        super.computeScroll();        if (!isInEditMode() && (viewDragHelper != null) && viewDragHelper.continueSettling(true)) {            /*开启自动滑动*/            ViewCompat.postInvalidateOnAnimation(this);            invalidate();        }    }    private final class ViewDragHelperCallback extends ViewDragHelper.Callback {        /**         * 手指释放的时候回调         */        public void onViewReleased(View releasedChild, float xvel, float yvel) {            LogUtil.e("进来了");            // 拖动距离大于屏幕的一半右移，拖动距离小于屏幕的一半左移            int left = releasedChild.getLeft();            if (left > getWidth() / 2) {                viewDragHelper.settleCapturedViewAt(getWidth(), 0);                invalidate();            } else {                viewDragHelper.settleCapturedViewAt(0, 0);                invalidate();            }        }        /**         * 当captureview的位置发生改变时回调         */        @Override        public void onViewPositionChanged(View changedView, int left, int top, int dx, int dy) {            super.onViewPositionChanged(changedView, left, top, dx, dy);            LogUtil.e(" 进度 = " + left * 100 / screenWidth);            if (onSwipeBackListener != null) {                onSwipeBackListener.onSwipeProgress(left * 100 / screenWidth);            }            if (left >= (screenWidth - 4)) {                finish();            }        }        /**         * 当触摸到边界时回调。         */        public void onEdgeTouched(int edgeFlags, int pointerId) {            super.onEdgeTouched(edgeFlags, pointerId);            /**捕捉要拖拽的对象*/            viewDragHelper.captureChildView(rootView, pointerId);        }        /**         * true的时候会锁住当前的边界，false则unLock。         */        public boolean onEdgeLock(int edgeFlags) {            return false;        }        /**         * 在边界拖动时回调         * 返回值为true 可以滑动 ；为false 则不能滑动         */        public void onEdgeDragStarted(int edgeFlags, int pointerId) {            /*移动子 View*/            viewDragHelper.captureChildView(rootView, pointerId);        }        public int getViewHorizontalDragRange(View child) {            return getMeasuredWidth() - child.getMeasuredWidth();        }        /**         * 尝试捕获子view， 返回true表示允许。         *         * @param child     尝试捕获的view         * @param pointerId 指示器id？         */        public boolean tryCaptureView(View child, int pointerId) {            return false;        }        /**         * 处理水平方向上的拖动，返回值就是最终确定的移动的位置。         * 实际上就是判断如果这个坐标在layout之内 那我们就返回这个坐标值。         * 除此之外就是如果你的layout设置了padding的话，         * 也可以让子view的活动范围在padding之内的.         *         * @param child 被拖动到view         * @param left  移动到达的x轴的距离         * @param dx    建议的移动的x距离         */        public int clampViewPositionHorizontal(View child, int left, int dx) {            LogUtil.e("进来了");            /*拖动限制（大于左边界）*/            return Math.max(0, left);        }    }    private void finish() {        if (onSwipeBackListener != null) {            onSwipeBackListener.onSwipeProgress(100);            onSwipeBackListener.onFinish();        }        if (activity != null) {            activity.finish();        }        if (viewDragHelper != null) {            viewDragHelper.cancel();        }        if (rootView != null) {            rootView.destroyDrawingCache();        }        viewDragHelper = null;        rootView = null;        activity = null;    }    /**     * 获得屏幕高度     */    private int getScreenWidth() {        WindowManager wm = (WindowManager) getContext().getSystemService(Context.WINDOW_SERVICE);        DisplayMetrics outMetrics = new DisplayMetrics();        wm.getDefaultDisplay().getMetrics(outMetrics);        return outMetrics.widthPixels;    }}

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