launcher5.0-拖动讲解

图标拖动过程先长按，拖动，松开手指

launcher.java中setupViews方法，

 private void setupViews() {
        final DragController dragController = mDragController;

        mLauncherView = findViewById(R.id.launcher);
        mDragLayer = (DragLayer) findViewById(R.id.drag_layer);
        mWorkspace = (Workspace) mDragLayer.findViewById(R.id.workspace);
        mQsbDivider = findViewById(R.id.qsb_divider);
        mDockDivider = findViewById(R.id.dock_divider);

        mLauncherView.setSystemUiVisibility(View.SYSTEM_UI_FLAG_LAYOUT_FULLSCREEN);
        mWorkspaceBackgroundDrawable = getResources().getDrawable(R.drawable.workspace_bg);

        // Setup the drag layer
        mDragLayer.setup(this, dragController);

        // Setup the hotseat
        mHotseat = (Hotseat) findViewById(R.id.hotseat);
        if (mHotseat != null) {
            mHotseat.setup(this);
        }

        // Setup the workspace
        mWorkspace.setHapticFeedbackEnabled(false);
        mWorkspace.setOnLongClickListener(this);
        mWorkspace.setup(dragController);
        dragController.addDragListener(mWorkspace);

        // Get the search/delete bar
        mSearchDropTargetBar = (SearchDropTargetBar) mDragLayer.findViewById(R.id.qsb_bar);

        // Setup AppsCustomize
        mAppsCustomizeTabHost = (AppsCustomizeTabHost) findViewById(R.id.apps_customize_pane);
        mAppsCustomizeContent = (AppsCustomizePagedView)
                mAppsCustomizeTabHost.findViewById(R.id.apps_customize_pane_content);
        mAppsCustomizeContent.setup(this, dragController);

        // Setup the drag controller (drop targets have to be added in reverse order in priority)
        dragController.setDragScoller(mWorkspace);
        dragController.setScrollView(mDragLayer);
        dragController.setMoveTarget(mWorkspace);
        dragController.addDropTarget(mWorkspace);
        if (mSearchDropTargetBar != null) {
            mSearchDropTargetBar.setup(this, dragController);
        }
    }

 mWorkspace.setOnLongClickListener(this); 看 onLongClick 方法

  public boolean onLongClick(View v) {
        if (!isDraggingEnabled()) return false;
        if (isWorkspaceLocked()) return false;
        if (mState != State.WORKSPACE) return false;

        if (!(v instanceof CellLayout)) {
            v = (View) v.getParent().getParent();
        }

        resetAddInfo();
        CellLayout.CellInfo longClickCellInfo = (CellLayout.CellInfo) v.getTag();
        // This happens when long clicking an item with the dpad/trackball
        if (longClickCellInfo == null) {
            return true;
        }

        // The hotseat touch handling does not go through Workspace, and we always allow long press
        // on hotseat items.
        final View itemUnderLongClick = longClickCellInfo.cell;
        boolean allowLongPress = isHotseatLayout(v) || mWorkspace.allowLongPress();
        if (allowLongPress && !mDragController.isDragging()) {
            if (itemUnderLongClick == null) {
                // User long pressed on empty space
                mWorkspace.performHapticFeedback(HapticFeedbackConstants.LONG_PRESS,
                        HapticFeedbackConstants.FLAG_IGNORE_VIEW_SETTING);
                startWallpaper();
            } else {
                if (!(itemUnderLongClick instanceof Folder)) {
                    // User long pressed on an item
                    mWorkspace.startDrag(longClickCellInfo);
                }
            }
        }
        return true;
    }

如上：longClickCellInfo 在哪个cell中长按(桌面page或者hotseatlayout) ，itemUnderLongClick 是 被长按的view

如果 itemUnderLongClick 为空则长按空白区域 则执行startWallpaper()换壁纸，如果为非文件夹item（如app或者快捷方式）则执行

 mWorkspace.startDrag(longClickCellInfo) 拖拽。

void startDrag(CellLayout.CellInfo cellInfo) {
        View child = cellInfo.cell;

        // Make sure the drag was started by a long press as opposed to a long click.
        if (!child.isInTouchMode()) {
            return;
        }

        mDragInfo = cellInfo;
        child.setVisibility(INVISIBLE);
        CellLayout layout = (CellLayout) child.getParent().getParent();
        layout.prepareChildForDrag(child);

        child.clearFocus();
        child.setPressed(false);

        final Canvas canvas = new Canvas();

        // The outline is used to visualize where the item will land if dropped
        mDragOutline = createDragOutline(child, canvas, DRAG_BITMAP_PADDING);
        beginDragShared(child, this);
    }

createDragOutline(child, canvas, DRAG_BITMAP_PADDING) 长按后创建移动的投影边框

beginDragShared(child, this)开始拖拽移动

public void beginDragShared(View child, DragSource source) {
        Resources r = getResources();

        // The drag bitmap follows the touch point around on the screen
        final Bitmap b = createDragBitmap(child, new Canvas(), DRAG_BITMAP_PADDING);

        final int bmpWidth = b.getWidth();
        final int bmpHeight = b.getHeight();

        float scale = mLauncher.getDragLayer().getLocationInDragLayer(child, mTempXY);
        int dragLayerX =
                Math.round(mTempXY[0] - (bmpWidth - scale * child.getWidth()) / 2);
        int dragLayerY =
                Math.round(mTempXY[1] - (bmpHeight - scale * bmpHeight) / 2
                        - DRAG_BITMAP_PADDING / 2);

        Point dragVisualizeOffset = null;
        Rect dragRect = null;
        if (child instanceof BubbleTextView || child instanceof PagedViewIcon) {
            int iconSize = r.getDimensionPixelSize(R.dimen.app_icon_size);
            int iconPaddingTop = r.getDimensionPixelSize(R.dimen.app_icon_padding_top);
            int top = child.getPaddingTop();
            int left = (bmpWidth - iconSize) / 2;
            int right = left + iconSize;
            int bottom = top + iconSize;
            dragLayerY += top;
            // Note: The drag region is used to calculate drag layer offsets, but the
            // dragVisualizeOffset in addition to the dragRect (the size) to position the outline.
            dragVisualizeOffset = new Point(-DRAG_BITMAP_PADDING / 2,
                    iconPaddingTop - DRAG_BITMAP_PADDING / 2);
            dragRect = new Rect(left, top, right, bottom);
        } else if (child instanceof FolderIcon) {
            int previewSize = r.getDimensionPixelSize(R.dimen.folder_preview_size);
            dragRect = new Rect(0, 0, child.getWidth(), previewSize);
        }

        // Clear the pressed state if necessary
        if (child instanceof BubbleTextView) {
            BubbleTextView icon = (BubbleTextView) child;
            icon.clearPressedOrFocusedBackground();
        }

        mDragController.startDrag(b, dragLayerX, dragLayerY, source, child.getTag(),
                DragController.DRAG_ACTION_MOVE, dragVisualizeOffset, dragRect, scale);
        b.recycle();

        // Show the scrolling indicator when you pick up an item
        showScrollingIndicator(false);
    }

final Bitmap b = createDragBitmap(child, new Canvas(), DRAG_BITMAP_PADDING);创建了图标图片

 float scale = mLauncher.getDragLayer().getLocationInDragLayer(child, mTempXY);获取scale图标缩放比和mTempXY所方比后的左上角坐标

dragLayerX，dragLayerY 拖动图标的显示位置

执行

mDragController.startDrag(b, dragLayerX, dragLayerY, source, child.getTag(),DragController.DRAG_ACTION_MOVE, dragVisualizeOffset, dragRect, scale);
交给mDragController.startDrag去执行拖动

public void startDrag(Bitmap b, int dragLayerX, int dragLayerY,
            DragSource source, Object dragInfo, int dragAction, Point dragOffset, Rect dragRegion,
            float initialDragViewScale) {
        if (PROFILE_DRAWING_DURING_DRAG) {
            android.os.Debug.startMethodTracing("Launcher");
        }

        // Hide soft keyboard, if visible
        if (mInputMethodManager == null) {
            mInputMethodManager = (InputMethodManager)
                    mLauncher.getSystemService(Context.INPUT_METHOD_SERVICE);
        }
        mInputMethodManager.hideSoftInputFromWindow(mWindowToken, 0);

        for (DragListener listener : mListeners) {
            listener.onDragStart(source, dragInfo, dragAction);
        }

        final int registrationX = mMotionDownX - dragLayerX;
        final int registrationY = mMotionDownY - dragLayerY;

        final int dragRegionLeft = dragRegion == null ? 0 : dragRegion.left;
        final int dragRegionTop = dragRegion == null ? 0 : dragRegion.top;

        mDragging = true;

        mDragObject = new DropTarget.DragObject();

        mDragObject.dragComplete = false;
        mDragObject.xOffset = mMotionDownX - (dragLayerX + dragRegionLeft);
        mDragObject.yOffset = mMotionDownY - (dragLayerY + dragRegionTop);
        mDragObject.dragSource = source;
        mDragObject.dragInfo = dragInfo;

        mVibrator.vibrate(VIBRATE_DURATION);

        final DragView dragView = mDragObject.dragView = new DragView(mLauncher, b, registrationX,
                registrationY, 0, 0, b.getWidth(), b.getHeight(), initialDragViewScale);

        if (dragOffset != null) {
            dragView.setDragVisualizeOffset(new Point(dragOffset));
        }
        if (dragRegion != null) {
            dragView.setDragRegion(new Rect(dragRegion));
        }

        dragView.show(mMotionDownX, mMotionDownY);
        handleMoveEvent(mMotionDownX, mMotionDownY);
    }

生成当前的拖动mDragObject对象 含有拖动信息 如dragInfo 坐标信息

mMotionDownX，mMotionDownY 手指按下的坐标

 dragView.show(mMotionDownX, mMotionDownY) 显示拖动view

 其他 图标移位，图标晃动等交给  handleMoveEvent(mMotionDownX, mMotionDownY)处理 ，handleMoveEvent在onTouchEvent中也有调用，拖动中不断调用

public boolean onTouchEvent(MotionEvent ev) {
        if (!mDragging) {
            return false;
        }

        // Update the velocity tracker
        acquireVelocityTrackerAndAddMovement(ev);

        final int action = ev.getAction();
        final int[] dragLayerPos = getClampedDragLayerPos(ev.getX(), ev.getY());
        final int dragLayerX = dragLayerPos[0];
        final int dragLayerY = dragLayerPos[1];

        switch (action) {
        case MotionEvent.ACTION_DOWN:
            // Remember where the motion event started
            mMotionDownX = dragLayerX;
            mMotionDownY = dragLayerY;

            if ((dragLayerX < mScrollZone) || (dragLayerX > mScrollView.getWidth() - mScrollZone)) {
                mScrollState = SCROLL_WAITING_IN_ZONE;
                mHandler.postDelayed(mScrollRunnable, SCROLL_DELAY);
            } else {
                mScrollState = SCROLL_OUTSIDE_ZONE;
            }
            break;
        case MotionEvent.ACTION_MOVE:
            handleMoveEvent(dragLayerX, dragLayerY);

看下方法 handleMoveEvent

private void handleMoveEvent(int x, int y) {
        mDragObject.dragView.move(x, y);

        // Drop on someone?
        final int[] coordinates = mCoordinatesTemp;
        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
        mDistanceSinceScroll +=
            Math.sqrt(Math.pow(mLastTouch[0] - x, 2) + Math.pow(mLastTouch[1] - y, 2));
        mLastTouch[0] = x;
        mLastTouch[1] = y;
        checkScrollState(x, y);
    }

先分析DropTarget类  

public interface DropTarget {

   ...


    void onDrop(DragObject dragObject);

    void onDragEnter(DragObject dragObject);

    void onDragOver(DragObject dragObject);

    void onDragExit(DragObject dragObject);

    ...
}

• onDragEnter是当拖动图标到某一DropTarget(蓝色),边缘，刚刚进入DropTarget范围内的时候所调用的内容。比如说我们拖动桌面的一个快捷方式，到桌面顶端的删除区域，“删除”两字和手中的图标会变红，这些动作都是在onDragEnter回调中完成的
• onDragOver是在某一DropTarget内部移动的时候会调用的回调，比如我们把手上的图标移动到两个图标中间的时候，会发生挤位的情况（就是桌面已有图标让出空位），基本上每个ACTION_MOVE操作都会调用他。
• onDragExit是从某一DropTarget拖出时候会进行的回调，比如onDragEnter时变红的“删除”和图标会在这个调用中恢复正常。
• onDrop是松手时候发生的调用，做一些放下时候的操作，比如删除快捷方式的时候会在onDrop里面开始删除的操作。

右键 open Type Hierchy 显示 继承DropTarget 三个类 分别是 ButtonDropTarge(长按后显示的删除区域)  Folder（文件夹） Workspace （桌面区域）

接着分析handleMoveEvent

int x, int y 是当前手指拖动坐标

DropTarget dropTarget = findDropTarget(x, y, coordinates); 表示拖动到删除区域，文件夹还是在左面工作区

 checkTouchMove(dropTarget);函数

 private void checkTouchMove(DropTarget dropTarget) {
        if (dropTarget != null) {
            DropTarget delegate = dropTarget.getDropTargetDelegate(mDragObject);
            if (delegate != null) {
                dropTarget = delegate;
            }

            if (mLastDropTarget != dropTarget) {
                if (mLastDropTarget != null) {
                    mLastDropTarget.onDragExit(mDragObject);
                }
                dropTarget.onDragEnter(mDragObject);
            }
            dropTarget.onDragOver(mDragObject);
        } else {
            if (mLastDropTarget != null) {
                mLastDropTarget.onDragExit(mDragObject);
            }
        }
        mLastDropTarget = dropTarget;
    }

设置各种效果 具体在DropTarget实现类中

checkScrollState 检查是否拖动到桌面边缘 触法Scroll效果

这就是拖动过程 接下来看手指松开代码 DragControler onTouchEvent

     case MotionEvent.ACTION_UP:
            // Ensure that we've processed a move event at the current pointer location.
            handleMoveEvent(dragLayerX, dragLayerY);
            mHandler.removeCallbacks(mScrollRunnable);

            if (mDragging) {
                PointF vec = isFlingingToDelete(mDragObject.dragSource);
                if (vec != null) {
                    dropOnFlingToDeleteTarget(dragLayerX, dragLayerY, vec);
                } else {
                    drop(dragLayerX, dragLayerY);
                }
            }
            endDrag();
            break;

 PointF vec = isFlingingToDelete(mDragObject.dragSource);是否是删除图标
删除图标执行dropOnFlingToDeleteTarget(dragLayerX, dragLayerY, vec);
否则执行drop(dragLayerX, dragLayerY);