---

前言

由于WPF 默认的Popup总是显示在所有窗口的前面，如何让popup 层只显示在该父级之上，并随着父级而动呢？下面来看实现。

---

一、定义类继承Popup类

public class PopupEx : Popup
{/// <summary>  /// 是否窗口随动，默认为随动（true）  /// </summary>  public bool IsPositionUpdate{get { return (bool)GetValue(IsPositionUpdateProperty); }set { SetValue(IsPositionUpdateProperty, value); }}public static readonly DependencyProperty IsPositionUpdateProperty =DependencyProperty.Register("IsPositionUpdate", typeof(bool), typeof(PopupEx), new PropertyMetadata(true, new PropertyChangedCallback(IsPositionUpdateChanged)));private static void IsPositionUpdateChanged(DependencyObject d, DependencyPropertyChangedEventArgs e){(d as PopupEx).pup_Loaded(d as PopupEx, null);}/// <summary>  /// 加载窗口随动事件  /// </summary>  public PopupEx(){this.Loaded += pup_Loaded;}/// <summary>  /// 加载窗口随动事件  /// </summary>  private void pup_Loaded(object sender, RoutedEventArgs e){Popup pup = sender as Popup;var win = VisualTreeHelper.GetParent(pup);while (win != null && (win as Window) == null){win = VisualTreeHelper.GetParent(win);}if ((win as Window) != null){(win as Window).LocationChanged -= PositionChanged;(win as Window).SizeChanged -= PositionChanged;if (IsPositionUpdate){(win as Window).LocationChanged += PositionChanged;(win as Window).SizeChanged += PositionChanged;}}}/// <summary>  /// 刷新位置  /// </summary>  private void PositionChanged(object sender, EventArgs e){try{var method = typeof(Popup).GetMethod("UpdatePosition", System.Reflection.BindingFlags.NonPublic | System.Reflection.BindingFlags.Instance);if (this.IsOpen){method.Invoke(this, null);}}catch{return;}}//是否最前默认为非最前（false）  public static DependencyProperty TopmostProperty = Window.TopmostProperty.AddOwner(typeof(Popup), new FrameworkPropertyMetadata(false, OnTopmostChanged));public bool Topmost{get { return (bool)GetValue(TopmostProperty); }set { SetValue(TopmostProperty, value); }}private static void OnTopmostChanged(DependencyObject obj, DependencyPropertyChangedEventArgs e){(obj as PopupEx).UpdateWindow();}/// <summary>  /// 重写拉开方法，置于非最前  /// </summary>  /// <param name="e"></param>  protected override void OnOpened(EventArgs e){UpdateWindow();}/// <summary>  /// 刷新Popup层级  /// </summary>  private void UpdateWindow(){var hwnd = ((HwndSource)PresentationSource.FromVisual(this.Child)).Handle;RECT rect;if (NativeMethods.GetWindowRect(hwnd, out rect)){NativeMethods.SetWindowPos(hwnd, Topmost ? -1 : -2, rect.Left, rect.Top, (int)this.Width, (int)this.Height, 0);}}[StructLayout(LayoutKind.Sequential)]public struct RECT{public int Left;public int Top;public int Right;public int Bottom;}#region P/Invoke imports & definitions  public static class NativeMethods{[DllImport("user32.dll")][return: MarshalAs(UnmanagedType.Bool)]internal static extern bool GetWindowRect(IntPtr hWnd, out RECT lpRect);[DllImport("user32", EntryPoint = "SetWindowPos")]internal static extern int SetWindowPos(IntPtr hWnd, int hwndInsertAfter, int x, int y, int cx, int cy, int wFlags);}#endregion
}

二、使用

1.在XAML头部加入链接

 xmlns:Component="clr-namespace:ZzgkChatRoom.Component"

2. 在XAML文件使用

代码如下（示例）：

  <Buttonx:Name="EmojiBtn"Grid.Column="0"Margin="0,0,0,0"HorizontalAlignment="Left"VerticalAlignment="Center"Click="EmojiBtn_Click"Content="0 2 0 0"Style="{StaticResource ChatBottomBtn}"Tag="{x:Static Icon:PackIconVaadinIconsKind.SmileyOutline}" /><Component:PopupExx:Name="EmojiPop"AllowsTransparency="True"HorizontalOffset="-40"IsOpen="False"Placement="Top"PlacementTarget="{Binding ElementName=EmojiBtn}"VerticalOffset="-5"><BorderWidth="400"Height="200"Background="#ffffff"BorderBrush="#646465"BorderThickness="1"CornerRadius="3" /></Component:PopupEx>

---

总结