Workspace 拖拽

workspace 的事件处里流程

设置workspace 的点击事件 在Launcher里面处理

mWorkspace.setOnLongClickListener(this);

1、launcher 中的长按事件将会回调到workspace

if (!(itemUnderLongClick instanceof Folder || isAllAppsButton)) {     // User long pressed on an item     mWorkspace.startDrag(longClickCellInfo);}

2、workspace 中的回调方法

-->startDrag(cellInfo, false);-->隐藏要拖拽的   Viewchild.setVisibility(INVISIBLE);-->准备当前CellLayout 数据  layout.prepareChildForDrag(child);-->开始拖拽 beginDragShared(child, this, accessible);

3、beginDragShared

// The outline is used to visualize where the item will land if dropped    //创建拖拽阴影mDragOutline = createDragOutline(child, DRAG_BITMAP_PADDING);-->//是否要回到默认屏幕 mLauncher.onDragStarted(child);-->//创建拖拽view Bitmap  createDragBitmap(child, padding);-->//当前view 在 draylayer 上的坐标（位置）计算拖拽时的 rect -->//调用DragController 开始拖拽并返回正在拖拽时的view -->//DragView dv = mDragController.startDrag(b, dragLayerX, dragLayerY, source, child.getTag(),                DragController.DRAG_ACTION_MOVE, dragVisualizeOffset, dragRect, scale, accessible);        参数：  B：位图显示拖动图像。它将re-scaled扩大规模。  DragLayer dragLayerX ：DragLayer 上的x位置  DragLayer dragLayerY ：DragLayer 上的y位置  source源对象代表拖源自哪里（workpace）  dragInfo:与被拖动的对象相关的数据  dragAction:拖动行动:DRAG_ACTION_MOVE或  DRAG_ACTION_COPY        dragRegion:坐标内的位图b项被拖动的位置。让拖感觉更精确,例如你可以夹一个透明的边界        访问这个阻力是否应该发生在可访问性模式        dragOffset:        initialDragViewScale:-->//对正在拖拽的view 进行设置缩放 dv.setIntrinsicIconScaleFactor         (source.getIntrinsicIconScaleFactor());

4、mDragController.startDrag

 -->先隐藏输入法，假如输入法正显示 -->//对注册DragListener 监听的进行回调 通知拖拽开始 for (DragListener listener : mListeners) {     listener.onDragStart(source, dragInfo, dragAction);} -->创建拖拽对象DropTarget.DragObject(); -->创建拖拽时的View -->显示拖拽view ，并拖拽实现dragView.show(mMotionDownX, mMotionDownY);handleMoveEvent(mMotionDownX, mMotionDownY);

5、handleMoveEvent(mMotionDownX, mMotionDownY);

private void handleMoveEvent(int x, int y) {  //移动到传进来时的参数        mDragObject.dragView.move(x, y);        // Drop on someone?        final int[] coordinates = mCoordinatesTemp;  //查找放下目标        DropTarget dropTarget = findDropTarget(x, y, coordinates);        mDragObject.x = coordinates[0];        mDragObject.y = coordinates[1];        checkTouchMove(dropTarget);        // Check if we are hovering over the scroll areas              //检查如果我们滚动区域的上空        mDistanceSinceScroll += Math.hypot(mLastTouch[0] - x, mLastTouch[1] - y);        mLastTouch[0] = x;        mLastTouch[1] = y;        checkScrollState(x, y);    }-->findDropTarget();查找当前放下的target及坐标-->checkTouchMove(dropTarget);//检查触摸移动private void checkTouchMove(DropTarget dropTarget) {        if (dropTarget != null) {            if (mLastDropTarget != dropTarget) {//最后一个DropTarget 不=于当前DropTarget                 if (mLastDropTarget != null) {                    mLastDropTarget.onDragExit(mDragObject);//退出当前的                }                dropTarget.onDragEnter(mDragObject);//进入当前的            }            dropTarget.onDragOver(mDragObject);        } else {            if (mLastDropTarget != null) {                mLastDropTarget.onDragExit(mDragObject);            }        }        mLastDropTarget = dropTarget;}--> //检查是否要移别的前一屏或者后一屏checkScrollState(x, y); @Thunk void checkScrollState(int x, int y) {        final int slop = ViewConfiguration.get(mLauncher).getScaledWindowTouchSlop();//                                                     触摸窗体边沿区域判断        final int delay = mDistanceSinceScroll < slop ? RESCROLL_DELAY : SCROLL_DELAY;//         final DragLayer dragLayer = mLauncher.getDragLayer();        final int forwardDirection = mIsRtl ? SCROLL_RIGHT : SCROLL_LEFT;        final int backwardsDirection = mIsRtl ? SCROLL_LEFT : SCROLL_RIGHT;        if (x < mScrollZone) {//边缘判断            if (mScrollState == SCROLL_OUTSIDE_ZONE) {                mScrollState = SCROLL_WAITING_IN_ZONE;                if (mDragScroller.onEnterScrollArea(x, y, forwardDirection)) {//判断是否                                                            //能发生滚动                    dragLayer.onEnterScrollArea(forwardDirection);                    mScrollRunnable.setDirection(forwardDirection);                    mHandler.postDelayed(mScrollRunnable, delay);                }            }        } else if (x > mScrollView.getWidth() - mScrollZone) {//边缘判断            if (mScrollState == SCROLL_OUTSIDE_ZONE) {                mScrollState = SCROLL_WAITING_IN_ZONE;                if (mDragScroller.onEnterScrollArea(x, y, backwardsDirection)) {                    dragLayer.onEnterScrollArea(backwardsDirection);                    mScrollRunnable.setDirection(backwardsDirection);                    mHandler.postDelayed(mScrollRunnable, delay);                }            }        } else {            clearScrollRunnable();        }    }

6、MotionEvent.ACTION_UP:

PointF  isFlingingToDelete(DragSource source)//是否甩动删除dropOnFlingToDeleteTarget(dragLayerX, dragLayerY, vec);drop(dragLayerX, dragLayerY);endDrag();

7、DropTarget


onDrop：就是在放下后做的操作；
onDragEnter：进入之后的操作；
onDragOver：在目标体之上做的操作；
onDragExit：退出之后的操作；