Question

我有一个TreeView。我在TreeViewItems上设置了ContextMenu。当我通过右键单击某个项目并选择另一个项目（当ContextMenu打开时）打开ContextMenu时，我希望刚刚单击的项目无需任何操作即可被选中。相反，框架认为我想拖动打开ContextMenu的项目，因此调用Drop处理程序。我怎么解决这个问题。感谢

  private void TreeViewPreviewMouseMove(object sender, MouseEventArgs e)
    {
        if (e.LeftButton == MouseButtonState.Pressed && !_isDragging)
        {
            var position = e.GetPosition(sender as IInputElement);
            if (Math.Abs(position.X - _startPoint.X) > SystemParameters.MinimumHorizontalDragDistance ||
                Math.Abs(position.Y - _startPoint.Y) > SystemParameters.MinimumVerticalDragDistance)
            {
                StartDrag();
            }
        }  
    }

    private void TreeViewPreviewMouseLeftButtonDown(object sender, MouseButtonEventArgs e)
    {
        _startPoint = e.GetPosition(sender as IInputElement);
    }

    private void TemplateTreeViewDrop(object sender, DragEventArgs e)
    {
        if (_isDragging && (e.Source as TreeView) != null)
        {                
          dragQuestion = e.Data.GetData(typeof(QuestionListItem)) as QuestionListItem;
          dropQuestion = GetItemAtLocation(e.GetPosition(TemplateTreeView));
            if (dragQuestion != null && dropQuestion != null && dragQuestion!=dropQuestion)
            {
                viewModel.MoveQuestion(dragQuestion, dropQuestion);
            }
        }
        e.Handled = true;
        dragQuestion = null;
    }

    private void StartDrag()
    {
        var temp = TemplateTreeView.SelectedItem as QuestionListItem;
        if(temp == null) return;

        _isDragging = true;
        var data = new DataObject(temp);
        DragDrop.DoDragDrop(TemplateTreeView, data, DragDropEffects.Move);
        _isDragging = false;
    }

Answer 1

根据您发布的代码判断，在您的场景中永远不应该调用StartDrag方法。但很明显，因为你最终会进行掉落和放弃操作。在那里放一个断点，你应该明白为什么叫它。

旁注，此代码

_isDragging = true;
var data = new DataObject(temp);
DragDrop.DoDragDrop(TemplateTreeView, data, DragDropEffects.Move);
_isDragging = false;

不安全。你应该使用try / finally：

_isDragging = true;

try
{
    var data = new DataObject(temp);
    DragDrop.DoDragDrop(TemplateTreeView, data, DragDropEffects.Move);
}
finally
{
    _isDragging = false;
}

编辑：正如Dtex建议的那样，您也可以尝试替换您的e.GetPosition（发件人为IInputElement）; e.GetPosition的声明（System.Windows.Application.Current.MainWindow）

Answer 2

我发现了问题：在StartDrag方法中“var temp = TemplateTreeView.SelectedItem as QuestionListItem”我改变了var temp = GetItemAtLocation（e.GetPosition（TemplateTreeView））;

Answer 3

尝试在theContextMenu.IsVisible之前检查StartDrag

WPF - 树视图 - 拖放和上下文菜单问题

3 个答案: