Question

我正在尝试在同一控件中实现treeview项的DragDrop。

我希望能够将一个项目从一个节点移动到另一个节点。

这是我当前的代码，当我运行这个时，我可以看到该项目已经开始拖动，但是windows图标不允许它被删除到Control上的任何节点。

我当前的代码

private void treeView1_ItemDrag(object sender, ItemDragEventArgs e)
{
    DoDragDrop(e.Item, DragDropEffects.Move);
}

private void treeView1_DragEnter(object sender, DragEventArgs e)
{
    e.Effect = DragDropEffects.Move;
}

private void treeView1_DragDrop(object sender, DragEventArgs e)
{
    if (e.Data.GetDataPresent(typeof(TreeNode)))
    {
        TreeNode sourceNode = e.Data.GetData(typeof(TreeView)) as TreeNode;

        var item = new TreeNode(sourceNode.Text);


        System.Drawing.Point pt = ((TreeView)sender).PointToClient(new System.Drawing.Point(e.X, e.Y));
        TreeNode DestinationNode = ((TreeView)sender).GetNodeAt(pt);

        DestinationNode.Nodes.Add(item);
        DestinationNode.Expand();
    }
}

Answer 1

只需将treeView1_DragDrop功能修改为：

即可

private void treeView1_DragDrop(object sender, DragEventArgs e)
{
    // Retrieve the client coordinates of the drop location.
    Point targetPoint = treeView1.PointToClient(new Point(e.X, e.Y));

    // Retrieve the node at the drop location.
    TreeNode targetNode = treeView1.GetNodeAt(targetPoint);

    // Retrieve the node that was dragged.
    TreeNode draggedNode = (TreeNode)e.Data.GetData(typeof(TreeNode));

    // Confirm that the node at the drop location is not 
    // the dragged node and that target node isn't null
    // (for example if you drag outside the control)
    if (!draggedNode.Equals(targetNode) && targetNode != null)
    {
        // Remove the node from its current 
        // location and add it to the node at the drop location.
        draggedNode.Remove();
        targetNode.Nodes.Add(draggedNode);

        // Expand the node at the location 
        // to show the dropped node.
        targetNode.Expand();
    }
}

Answer 2

在树形控件上设置AllowDrop=true。

Answer 3

稍微改进的版本，阻止您将节点放到自身或其任何后代上

private void treeView1_DragDrop(object sender, DragEventArgs e)
{
    TreeNode draggedNode = (MatfloNode)drgevent.Data.GetData(typeof(TreeNode));

    Point pt = this.PointToClient(new System.Drawing.Point(drgevent.X, drgevent.Y));
    TreeNode targetNode = this.GetNodeAt(pt);

    TreeNode parentNode = targetNode;

    if (draggedNode != null &&
        targetNode != null  )
    {
        bool canDrop = true;
        while (canDrop && (parentNode != null))
        {
            canDrop = !Object.ReferenceEquals(draggedNode, parentNode);
            parentNode = parentNode.Parent;
        }

        if (canDrop)
        {
            draggedNode.Remove();
            targetNode.Nodes.Add(draggedNode);
            targetNode.Expand();
        }
    }
}

Answer 4

DragDrop处理程序的一些改进和补充，以与所有其他修订一起使用。

添加了支持：

支持将节点拖放到树视图背景（底部）。节点被添加到树的底部。
注意不要放弃子节点＆＃34;例如，通过mrpurple并修饰它，使其与原始示例内联。
也使得拖动的节点在被删除后被选中。建议在此处加载已删除节点的内容用户可能会对当前显示的内容与选择的节点感到困惑。

注意：确保树视图控件上的AllowDrop = true，否则您无法删除节点。

private void treeView1_ItemDrag(object sender, ItemDragEventArgs e)
{
    DoDragDrop(e.Item, DragDropEffects.Move);
}

private void treeView1_DragEnter(object sender, DragEventArgs e)
{
    e.Effect = DragDropEffects.Move;
}

private void treeView1_DragDrop(object sender, DragEventArgs e)
{
    // Retrieve the client coordinates of the drop location.
    Point targetPoint = treeView1.PointToClient(new Point(e.X, e.Y));

    // Retrieve the node at the drop location.
    TreeNode targetNode = treeView1.GetNodeAt(targetPoint);

    // Retrieve the node that was dragged.
    TreeNode draggedNode = e.Data.GetData(typeof(TreeNode));

    // Sanity check
    if (draggedNode == null)
    {
        return;
    }

    // Did the user drop on a valid target node?
    if (targetNode == null)
    {
        // The user dropped the node on the treeview control instead
        // of another node so lets place the node at the bottom of the tree.
        draggedNode.Remove();
        treeView1.Nodes.Add(draggedNode);
        draggedNode.Expand();
    }
    else
    {
        TreeNode parentNode = targetNode;

        // Confirm that the node at the drop location is not 
        // the dragged node and that target node isn't null
        // (for example if you drag outside the control)
        if (!draggedNode.Equals(targetNode) && targetNode != null)
        {
            bool canDrop = true;

            // Crawl our way up from the node we dropped on to find out if
            // if the target node is our parent. 
            while (canDrop && (parentNode != null))
            {
                canDrop = !Object.ReferenceEquals(draggedNode, parentNode);
                parentNode = parentNode.Parent;
            }

            // Is this a valid drop location?
            if (canDrop)
            {
                // Yes. Move the node, expand it, and select it.
                draggedNode.Remove();
                targetNode.Nodes.Add(draggedNode);
                targetNode.Expand();
            }
        }
    }

    // Optional: Select the dropped node and navigate (however you do it)
    treeView1.SelectedNode = draggedNode;
    // NavigateToContent(draggedNode.Tag);
}

C＃WinForms - DragDrop在同一个TreeViewControl中

4 个答案: