“父窗口拖动的时候Popup不随着父窗口移动”问题的解决方案

我们用WPF用的Popup时候会发现，当 StaysOpen=True 的时候，因为Popup不会消失，在父窗口移走的时候Popup仍旧在原地。。。作者在国外网站上无意间发现了这个解决方案，拿出来给大家分享：

方法是为Popup定义一个附加属性。代码如下。

     public class PopopHelper
     {
         public static DependencyObject GetPopupPlacementTarget(DependencyObject obj)
         {
             return (DependencyObject)obj.GetValue(PopupPlacementTargetProperty);
         }

         public static void SetPopupPlacementTarget(DependencyObject obj, DependencyObject value)
         {
             obj.SetValue(PopupPlacementTargetProperty, value);
         }

         // Using a DependencyProperty as the backing store for PopupPlacementTarget.  This enables animation, styling, binding, etc...
         public static readonly DependencyProperty PopupPlacementTargetProperty =
             DependencyProperty.RegisterAttached("PopupPlacementTarget", typeof(DependencyObject), typeof(PopopHelper), new PropertyMetadata(null,OnPopupPlacementTargetChanged));

         private static void OnPopupPlacementTargetChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
         {
             if (e.NewValue != null)
             {
                 DependencyObject popupPopupPlacementTarget = e.NewValue as DependencyObject;
                 Popup pop = d as Popup;

                 Window w = Window.GetWindow(popupPopupPlacementTarget);
                 if (null != w)
                 {
                     w.LocationChanged += delegate
                     {
                         var offset = pop.HorizontalOffset;
                         pop.HorizontalOffset = offset + ;
                         pop.HorizontalOffset = offset;
                     };
                 }
             }
         }

     }

之后只需要在Popup控件上这样写即可：

     <Grid>
         <TextBox x:Name="placementTextBox"/>
         <Popup PopopHelper.PopupPlacementTarget="{Binding ElementName=placementTextBox}" />
     </Grid>

本文的示例工程可以从附件下载。

欢迎各种转载，转载请注明来自 Leaco 的博客：http://www.cnblogs.com/Leaco/p/3168540.html