如何单独拖动SelectedItem附近的列表框Item

Question

我想拖动列表框中选定的项目。拖动功能运行良好。我的要求是，当从列表框中的任何其他位置开始拖动时，不应该发生拖动。我曾经这样做过，但那不起作用。请有人建议我实现这一点，

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;
}

请参阅屏幕截图

Answer 1

这样做，通过使用System.Windows.Media.VisualTreeHelper.HitTest(this, point)，它在鼠标下给出当前元素。我想这会对你有所帮助。

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);
}
}
}           
}