WPF 实现Popup不在最上层显示、随窗口移动

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）：

  <Button
      x: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:PopupEx
    	x:Name="EmojiPop"
    	AllowsTransparency="True"
   	 	HorizontalOffset="-40"
    	IsOpen="False"
    	Placement="Top"
   	 	PlacementTarget="{Binding ElementName=EmojiBtn}"
    	VerticalOffset="-5">
    <Border
        Width="400"
        Height="200"
        Background="#ffffff"
        BorderBrush="#646465"
        BorderThickness="1"
        CornerRadius="3" />
	</Component:PopupEx>

总结