21天打卡Andoid学到的一些小知识-第十一十二天

packages/apps/Launcher3/src/com/android/launcher3/Workspace.java
@Override
public void onDragStart(DropTarget.DragObject dragObject, DragOptions options) {
if (TestProtocol.sDebugTracing) {
android.util.Log.d(TestProtocol.NO_DRAG_TAG,
"onDragStart 1");
}
if (ENFORCE_DRAG_EVENT_ORDER) {
enforceDragParity("onDragStart", 0, 0);
}
    if (mDragInfo != null && mDragInfo.cell != null && mDragInfo.cell.getParent() != null) {
        CellLayout layout = (CellLayout) mDragInfo.cell.getParent().getParent();
        if (layout != null) layout.markCellsAsUnoccupiedForView(mDragInfo.cell);
    }
    if (mOutlineProvider != null) {
        if (dragObject.dragView != null) {
            Bitmap preview = dragObject.dragView.getPreviewBitmap();
            // The outline is used to visualize where the item will land if dropped
            mOutlineProvider.generateDragOutline(preview);
        }
    }
    updateChildrenLayersEnabled();
    // Do not add a new page if it is a accessible drag which was not started by the workspace.
    // We do not support accessibility drag from other sources and instead provide a direct
    // action for move/add to homescreen.
    // When a accessible drag is started by the folder, we only allow rearranging withing the
    // folder.
    boolean addNewPage = !(options.isAccessibleDrag && dragObject.dragSource != this);
    if (addNewPage) {
        mDeferRemoveExtraEmptyScreen = false;
        addExtraEmptyScreenOnDrag();
        if (dragObject.dragInfo.itemType == LauncherSettings.Favorites.ITEM_TYPE_APPWIDGET
                && dragObject.dragSource != this) {
            // When dragging a widget from different source, move to a page which has
            // enough space to place this widget (after rearranging/resizing). We special case
            // widgets as they cannot be placed inside a folder.
            // Start at the current page and search right (on LTR) until finding a page with
            // enough space. Since an empty screen is the furthest right, a page must be found.
            int currentPage = getPageNearestToCenterOfScreen();
            for (int pageIndex = currentPage; pageIndex < getPageCount(); pageIndex++) {
                CellLayout page = (CellLayout) getPageAt(pageIndex);
                if (page.hasReorderSolution(dragObject.dragInfo)) {
                    setCurrentPage(pageIndex);
                    break;
                }
            }
        }
    }
    // Always enter the spring loaded mode
    if (TestProtocol.sDebugTracing) {
        android.util.Log.d(TestProtocol.NO_DRAG_TAG,
                "onDragStart 2");
    }
    mLauncher.getStateManager().goToState(SPRING_LOADED);
}