Launcher2分析——桌面（WorkSpace）图标拖拽

最新推荐文章于 2022-08-16 16:55:41 发布

淡淡的宁静

最新推荐文章于 2022-08-16 16:55:41 发布

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分类专栏：移动开发综合 android系统相关

本文链接：https://blog.youkuaiyun.com/b1480521874/article/details/79718566

本文深入分析了Launcher2中桌面图标拖拽的过程，从长按图标触发拖拽模式开始，详细阐述了DragController、DragLayer、Workspace等组件如何协同工作，实现图标的拖放操作。

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长按图标触发进入拖拽模式：

在Launcher#setupViews（）为WorkSpace绑定了onLongClickListener。所以从Launcher#onLongClick（）开始：

Launcher#onLongClick（）

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

        if (!(v instanceof CellLayout)) {
//v.getParent()为ShortcutAndWidgetContainer，v.getParent().getParent()为CellLayout
            v = (View) v.getParent().getParent();
        }

        resetAddInfo();
        CellLayout.CellInfo longClickCellInfo = (CellLayout.CellInfo) v.getTag();//获取图标View的信息，往下传
        // 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);//进入Drag模式
                }
            }
        }
        return true;
    }

WorkSpace#startDrag(CellLayout.CellInfo cellInfo)

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 = cellI