如何单独拖动 SelectedItem 附近的列表框项

Question

我想拖动列表框选定的项目。拖动功能工作正常。我的要求是从列表框中的任何其他位置开始拖动时不应发生拖动。我做过这样的事情，但那是行不通的。请任何人建议我实现这一目标，

        private bool IsDragging { get; set; }
        private Point _startPoint { get; set; }        

        protected override void OnAttached()
        {                            
            this.AssociatedObject.PreviewMouseLeftButtonDown += AssociatedObject_PreviewMouseLeftButtonDown;
            this.AssociatedObject.PreviewMouseMove += AssociatedObject_PreviewMouseMove;

        }

        private void AssociatedObject_PreviewMouseMove(object sender, MouseEventArgs e)
        {
            if (e.LeftButton == MouseButtonState.Pressed && !IsDragging)
            {

                Point position = e.GetPosition(null);                      

                if (Math.Abs(position.X - _startPoint.X) <= SystemParameters.MinimumHorizontalDragDistance &&
                    Math.Abs(position.Y - _startPoint.Y) <= SystemParameters.MinimumVerticalDragDistance)
                {
                    StartDrag(sender);
                }
            }
        }

        private void AssociatedObject_PreviewMouseLeftButtonDown(object sender, MouseButtonEventArgs e)
        {
            _startPoint = e.GetPosition(null);
        }



        private void StartDrag(object sender)
        {

            IsDragging = true;

            if (sender is ListBox)
            {
                var listBox = (sender as ListBox);
                if (listBox != null)
                {
                    var selectedMember = listBox.SelectedItem;
                    if (selectedMember != null)
                    {
                        DragDrop.DoDragDrop(listBox, selectedMember, DragDropEffects.Copy);
                    }
                }
            }

            IsDragging = false;

        }

Please refer the screenshot

Answer 1

这样做，通过使用System.Windows.Media.VisualTreeHelper.HitTest(this, point)，它给出了鼠标下的当前元素。我想它会对你有所帮助。

private bool IsDrag { get; set; }              

        protected override void OnAttached()
        {            
            this.AssociatedObject.Drop += AssociatedObject_Drop;            
            this.AssociatedObject.PreviewMouseLeftButtonDown += AssociatedObject_PreviewMouseLeftButtonDown;
            this.AssociatedObject.PreviewMouseMove += AssociatedObject_PreviewMouseMove;

        }

        private void AssociatedObject_PreviewMouseMove(object sender, MouseEventArgs e)
        {                                  
            if (e.LeftButton == MouseButtonState.Pressed)
            {               
                if(IsDrag)
                {
                    StartDrag(sender);
                }
            }
        }

        private void AssociatedObject_PreviewMouseLeftButtonDown(object sender, MouseButtonEventArgs e)
        {
            IsDrag = false;    

            if(sender is ListBox)
            {
                Point initialPoint = e.GetPosition((UIElement)sender);
                var histPoint = VisualTreeHelper.HitTest(sender as ListBox, initialPoint);

                if (histPoint.VisualHit != null)
                {
                    if (histPoint.VisualHit is TextBlock || histPoint.VisualHit is Border)
                    {
                        IsDrag = true;
                    }
                }
            }            
        }                   

        private void StartDrag(object sender)
        {            
            if (sender is ListBox)
            {
                var listBox = (sender as ListBox);
                if (listBox != null)
                {
                    var selectedMember = listBox.SelectedItem;
                    if (selectedMember != null)
                    {
                        DragDrop.DoDragDrop(listBox, selectedMember, DragDropEffects.Copy);
                    }
                }
            }           
        }