什么可以是SWT树节点的拖动类型

Question

我有一个SWT树，它有图像和其他文本以及多级子项。 现在我想拖动这个树节点，但我无法为此获得正确的传输类型。 所以一旦我拖动我就不会得到拖动图像。 是否有可用的默认传输类型。

以下是我的树 -

我使用了以下转移但没有工作 -

Transfer[] types = new Transfer[] {FileTransfer.getInstance(),ImageTransfer.getInstance() };

Answer 1

我仍然不完全确定你要求的是什么，但这段代码甚至适用于Image。

如果您的文字不能用作标识符，您可以提出其他内容：

private static Map<String, Image>   mapping = new HashMap<String, Image>();

public static void main(String[] args)
{
    Display display = new Display();
    final Shell shell = new Shell(display);
    shell.setText("StackOverflow");
    shell.setLayout(new FillLayout());

    Tree tree = new Tree(shell, SWT.NONE);

    Image[] images = new Image[] { display.getSystemImage(SWT.ICON_WARNING),
            display.getSystemImage(SWT.ICON_ERROR), display.getSystemImage(SWT.ICON_INFORMATION),
            display.getSystemImage(SWT.ICON_QUESTION) };

    for (int i = 0; i < 10; i++)
    {
        TreeItem item = new TreeItem(tree, SWT.NONE);
        item.setText("Item " + i);
        item.setImage(images[i % images.length]);
        mapping.put("Item " + i, images[i % images.length]);
    }

    initDnD(display, tree);

    shell.pack();
    shell.open();
    while (!shell.isDisposed())
    {
        if (!display.readAndDispatch())
            display.sleep();
    }
    display.dispose();
}

private static void initDnD(final Display display, final Tree tree)
{
    Transfer[] types = new Transfer[] { TextTransfer.getInstance() };
    int operations = DND.DROP_MOVE | DND.DROP_COPY | DND.DROP_LINK;

    final DragSource source = new DragSource(tree, operations);
    source.setTransfer(types);

    final TreeItem[] dragSourceItem = new TreeItem[1];
    source.addDragListener(new DragSourceListener()
    {
        public void dragStart(DragSourceEvent event)
        {
            TreeItem[] selection = tree.getSelection();
            if (selection.length > 0 && selection[0].getItemCount() == 0)
            {
                event.doit = true;
                dragSourceItem[0] = selection[0];
            }
            else
            {
                event.doit = false;
            }
        };

        public void dragSetData(DragSourceEvent event)
        {
            event.data = dragSourceItem[0].getText();
        }

        public void dragFinished(DragSourceEvent event)
        {
            if (event.detail == DND.DROP_MOVE)
                dragSourceItem[0].dispose();
            dragSourceItem[0] = null;
        }
    });

    DropTarget target = new DropTarget(tree, operations);
    target.setTransfer(types);
    target.addDropListener(new DropTargetAdapter()
    {
        public void dragOver(DropTargetEvent event)
        {
            event.feedback = DND.FEEDBACK_SCROLL;
            if (event.item != null)
            {
                TreeItem item = (TreeItem) event.item;
                Point pt = display.map(null, tree, event.x, event.y);
                Rectangle bounds = item.getBounds();
                if (pt.y < bounds.y + bounds.height / 3)
                {
                    event.feedback |= DND.FEEDBACK_INSERT_BEFORE;
                }
                else if (pt.y > bounds.y + 2 * bounds.height / 3)
                {
                    event.feedback |= DND.FEEDBACK_INSERT_AFTER;
                }
            }
        }

        public void drop(DropTargetEvent event)
        {
            if (event.data == null)
            {
                event.detail = DND.DROP_NONE;
                return;
            }
            String text = (String) event.data;
            if (event.item != null)
            {
                TreeItem item = (TreeItem) event.item;
                Point pt = display.map(null, tree, event.x, event.y);
                Rectangle bounds = item.getBounds();

                TreeItem[] items = tree.getItems();
                int index = 0;
                for (int i = 0; i < items.length; i++)
                {
                    if (items[i] == item)
                    {
                        index = i;
                        break;
                    }
                }

                if (pt.y < bounds.y + bounds.height / 3)
                {
                    TreeItem newItem = new TreeItem(tree, SWT.NONE, index);
                    newItem.setText(text);
                    newItem.setImage(mapping.get(text));
                }
                else if (pt.y > bounds.y + 2 * bounds.height / 3)
                {
                    TreeItem newItem = new TreeItem(tree, SWT.NONE, index + 1);
                    newItem.setText(text);
                    newItem.setImage(mapping.get(text));
                }
                else
                {
                    TreeItem newItem = new TreeItem(item, SWT.NONE);
                    newItem.setText(text);
                    newItem.setImage(mapping.get(text));
                }
            }
        }
    });
}