我有一个这样定义的弹出窗口：
<Popup
Name="myPopup"
StaysOpen="True"
Placement="Bottom"
PlacementRectangle="0,20,0,20"
PlacementTarget="{Binding ElementName=myPopupAnchor}">
<TextBlock ... />
</Popup>
myPopupAnchor元素添加了MouseEnter和MouseLeave事件处理程序。这两个事件处理程序切换弹出窗口的可见性。myPopupAnchor的位置被读取。如果锚点移动，弹出窗口将不会移动。PlacementTarget已更改并应重新读取吗？我可以手动设置弹出窗口的位置吗？我查看了几个选项和示例。对我来说似乎最好的方法是“推动”一个导致弹出窗口自行重新定位的属性。我使用的属性是HorizontalOffset。
我将它设置为（它本身+1），然后将其设置回原始值。我在重新定位窗口时运行的事件处理程序中执行此操作。
// Reference to the PlacementTarget.
DependencyObject myPopupPlacementTarget;
// Reference to the popup.
Popup myPopup;
Window w = Window.GetWindow(myPopupPlacementTarget);
if (null != w)
{
w.LocationChanged += delegate(object sender, EventArgs args)
{
var offset = myPopup.HorizontalOffset;
myPopup.HorizontalOffset = offset + 1;
myPopup.HorizontalOffset = offset;
};
}
当窗口移动时，弹出控件将重新定位。由于窗口和弹出控件已经在移动，水平偏移量的微小变化不会被注意到。
我仍在评估在控件在其他交互期间保持打开状态的情况下，弹出控件是否是最佳选项。我认为Ray Burns建议将这些内容放入装饰层，对某些场景来说是一个很好的方法。
<UserControl x:Class="MyNamespace.View1"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" >
<TextBlock x:Name="popupTarget" />
<Popup x:Name="myPopup"
Placement="Bottom"
PlacementTarget="{Binding ElementName=popupTarget}" >
(popup content here)
</Popup>
</UserControl>
然后在代码后台，为了避免Window.GetWindow()返回Null，需要将处理程序与已加载事件绑定，以容纳NathanAW的代码（例如，请参见Peter Walke的评论的类似stackoverflow讨论）。以下是我的UserControl代码后台的完整内容：
public partial class View1 : UserControl
{
// Constructor
public View1()
{
InitializeComponent();
// Window.GetWindow() will return Null if you try to call it here!
// Wire up the Loaded handler instead
this.Loaded += new RoutedEventHandler(View1_Loaded);
}
/// Provides a way to "dock" the Popup control to the Window
/// so that the popup "sticks" to the window while the window is dragged around.
void View1_Loaded(object sender, RoutedEventArgs e)
{
Window w = Window.GetWindow(popupTarget);
// w should not be Null now!
if (null != w)
{
w.LocationChanged += delegate(object sender2, EventArgs args)
{
var offset = myPopup.HorizontalOffset;
// "bump" the offset to cause the popup to reposition itself
// on its own
myPopup.HorizontalOffset = offset + 1;
myPopup.HorizontalOffset = offset;
};
// Also handle the window being resized (so the popup's position stays
// relative to its target element if the target element moves upon
// window resize)
w.SizeChanged += delegate(object sender3, SizeChangedEventArgs e2)
{
var offset = myPopup.HorizontalOffset;
myPopup.HorizontalOffset = offset + 1;
myPopup.HorizontalOffset = offset;
};
}
}
}
private void ppValues_Opened(object sender, EventArgs e)
{
Window win = Window.GetWindow(YourControl);
win.LocationChanged += new EventHandler(win_LocationChanged);
}
void win_LocationChanged(object sender, EventArgs e)
{
if (YourPopup.IsOpen)
{
var mi = typeof(Popup).GetMethod("UpdatePosition", System.Reflection.BindingFlags.NonPublic | System.Reflection.BindingFlags.Instance);
mi.Invoke(YourPopup, null);
}
}
private存在是有原因的... - Marcel B除了Jason Frank的回答，如果WPF UserControl最终托管在WinForms ElementHost中，则Window.GetWindow()方法无法使用。我需要找到包含我的UserControl的ScrollViewer，因为它是显示滚动条的元素。
这个通用的递归方法（修改自另一个答案）将帮助在逻辑树中找到特定类型的父级（也可以使用可视树），并在找到时返回它。
public static T FindLogicalParentOf<T>(DependencyObject child) where T: FrameworkElement
{
DependencyObject parent = LogicalTreeHelper.GetParent(child);
//Top of the tree
if (parent == null) return null;
T parentWindow = parent as T;
if (parentWindow != null)
{
return parentWindow;
}
//Climb a step up
return FindLogicalParentOf<T>(parent);
}
使用这个辅助方法来代替Window.GetWindow()，并按照Jason的答案订阅正确的事件。在ScrollViewer的情况下，它是ScrollChanged事件。
IsOpen = false;
IsOpen = true;
我修改了Jason的代码，因为如果窗口没有激活，弹出窗口已经在前景中了。Popup类中有任何选项，还是我的解决方案可以吗？
private void FullLoaded(object sender, RoutedEventArgs e) {
Window CurrentWindow = Window.GetWindow(this.Popup);
if (CurrentWindow != null) {
CurrentWindow.LocationChanged += (object innerSender, EventArgs innerArgs) => {
this.RedrawPopup();
};
CurrentWindow.SizeChanged += (object innerSender, SizeChangedEventArgs innerArgs) => {
this.RedrawPopup();
};
CurrentWindow.Activated += (object innerSender, EventArgs innerArgs) => {
if (this.m_handleDeActivatedEvents && this.m_ShowOnActivated) {
this.Popup.IsOpen = true;
this.m_ShowOnActivated = false;
}
};
CurrentWindow.Deactivated += (object innerSender, EventArgs innerArgs) => {
if (this.m_handleDeActivatedEvents && this.Popup.IsOpen) {
this.Popup.IsOpen = false;
this.m_ShowOnActivated = true;
}
};
}
}
private void RedrawPopup() {
double Offset = this.Popup.HorizontalOffset;
this.Popup.HorizontalOffset = Offset + 1;
this.Popup.HorizontalOffset = Offset;
}
class MyPopup : Popup
{
private Window _root;
public MyPopup()
{
Loaded += OnLoaded;
Unloaded += OnUnloaded;
}
private void OnLoaded(object sender, RoutedEventArgs e)
{
_root = Window.GetWindow(this);
_root.LocationChanged += OnRootLocationChanged;
}
private void OnRootLocationChanged(object sender, EventArgs e)
{
var offset = this.HorizontalOffset;
this.HorizontalOffset = offset + 1;
this.HorizontalOffset = offset;
}
private void OnUnloaded(object sender, RoutedEventArgs e)
{
_root.LocationChanged -= OnRootLocationChanged;
Loaded -= OnLoaded;
Unloaded -= OnUnloaded;
}
}
查看https://referencesource.microsoft.com/#PresentationFramework/src/Framework/System/windows/Controls/Slider.cs，我们可以看到Popup类中有一个“Reposition()”方法，它能够很好地完成工作。但问题是，该方法是内部方法，可能在未来被取消。因此，在这种情况下，可能适合使用以下不正当手段：
internal class SampleClass
{
// Popup's Reposition() method adapter.
private static readonly Action<Popup> popupReposition = InitPopupReposition();
// Reference to the PlacementTarget.
DependencyObject myPopupPlacementTarget;
// Reference to the popup.
Popup myPopup;
private void SampleMethod()
{
// ...
Window w = Window.GetWindow(myPopupPlacementTarget);
if (null != w)
{
w.LocationChanged += delegate (object? sender, EventArgs args)
{
popupReposition(myPopup);
};
}
// ...
}
private static Action<Popup> InitPopupReposition()
{
var repositionMethod = typeof(Popup).GetMethod("Reposition", BindingFlags.Instance | BindingFlags.NonPublic);
if (repositionMethod != null)
{
// Use internal method if possible.
return new Action<Popup>(popup => repositionMethod.Invoke(popup, null));
}
// Fallback in case of internal implementation change.
return new Action<Popup>(popup =>
{
var offset = popup.HorizontalOffset;
popup.HorizontalOffset = offset + 1;
popup.HorizontalOffset = offset;
});
}
}
这种方法尽可能使用内部方法，如果内部实现发生变化，则使用备用方案。
你不能这样做。当弹出窗口显示在屏幕上时，如果其父级重新定位，它不会重新定位自己。这是 Popup 控件的行为。 请查看：http://msdn.microsoft.com/en-us/library/system.windows.controls.primitives.popup.aspx
你可以使用一个 Window（WindowStyle=None）代替 Popup，这可能解决你的问题。
在以下网址下载弹出窗口位置示例：
http://msdn.microsoft.com/en-us/library/ms771558(v=VS.90).aspx
代码示例使用了CustomPopupPlacement类和Rect对象，并绑定水平和垂直偏移量以移动弹出窗口。<Popup Name="popup1" Placement="Bottom" AllowsTransparency="True"
IsOpen="{Binding ElementName=popupOpen, Path=IsChecked}"
HorizontalOffset="{Binding ElementName=HOffset, Path=Value, Mode=TwoWay}"
VerticalOffset="{Binding ElementName=VOffset, Path=Value, Mode=TwoWay}"
ComboBox实现。但是我无法弄清楚它是如何移动Popup的。虽然没有关于ComboBox如何移动Popup的指导，但你有任何想法吗？ - amiry jdmyPopup.HorizontalOffset++; myPopup.HorizontalOffset--;。 - Danny Beckett