当弹出窗口 window 打开时，Windows 标题栏的最小化、最大化和关闭按钮在单击时不起作用

Question

当我的弹出窗口 window 打开时，第一次单击最小化或最大化或关闭按钮不起作用。 第一次单击这些标题栏按钮会关闭弹出菜单并移动焦点， 然后在第二次单击 window 的 minimize/maximize/close 有效。

有什么方法可以在第一次点击时激活这些标题栏按钮吗？

MainWindow.xaml

<Button Height="54" Width="50" Margin="100,0,0,0" x:Name="btnNotification"  FontFamily="Segoe UI Symbol" FontSize="20" Content="&#x1f514;" Command="{Binding LoadNotification}" Click="btnNotification_Click"/>

<Popup Name="NotificationPopup" IsOpen="False" Closed="PopupClosed" StaysOpen="False" PlacementTarget="{Binding ElementName=btnNotification}" Placement="Bottom" VerticalOffset="20">
    <Grid x:Name="PopUpGrid" Height="560" Width="360" Background="White">
        <StackPanel Orientation="Vertical" HorizontalAlignment="Right">
            <Button  BorderBrush="Transparent" BorderThickness="0" Background="White" >
                <StackPanel Width="{Binding ActualWidth, ElementName=PopUpGrid}" Orientation="Vertical">
                    <WrapPanel>
                        <Rectangle Width="20"/>
                        <TextBlock  Text="Notifications" Width="300" HorizontalAlignment="Left" VerticalAlignment="Top" FontSize="24" FontWeight="Light" />
                        <Button Click="btnNotification_Click" >
                            <StackPanel>
                                <TextBlock Text="&#x2715;" Foreground="Black" FontWeight="ExtraLight"/>
                            </StackPanel>
                        </Button>
                    </WrapPanel>
                    <Grid>
                            <!--Datagrid-->
                    </Grid>
                </StackPanel>
            </Button>
        </StackPanel>
    </Grid>
</Popup>

MainWindow.xaml.cs

public void PopupClosed(object sender, EventArgs e)
{
    NotificationPopup.IsOpen = false;               
}

Answer 1

您试图实现的目标违反了 'normal' Windows 行为。实际上，这是由操作系统管理的。

但如果您仍想覆盖默认操作系统的行为，则需要执行一些低级别的 Windows' 消息魔术。

我为您提供了一个解决方案，这是一个简单的附件 属性，您可以将其用于所有 Popup。就这样:

<Popup local:PopupMouseEnhance.Enabled="True">
    <!-- your content here -->
</Popup>

但是，幕后发生了一些事情，所以我会尝试解释一下。这是我为您创建的附件 属性 的完整来源。阅读评论以了解发生了什么。

static class PopupMouseEnhance
{
    // This is the usual attached property stuff...
    public static bool GetEnabled(UIElement element)
    {
        return (bool)element.GetValue(EnabledProperty);
    }

    public static void SetEnabled(UIElement element, bool value)
    {
        element.SetValue(EnabledProperty, value);
    }

    public static readonly DependencyProperty EnabledProperty =
        DependencyProperty.RegisterAttached(
            "Enabled",
             typeof(bool),
             typeof(PopupMouseEnhance),
             new PropertyMetadata(false, EnabledChanged));

    // This method is called when you set the attached property value
    private static void EnabledChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
    {
        Popup popup = d as Popup;
        if (popup == null)
        {
            // We don't support anything but Popups
            throw new InvalidOperationException("This attached property can only be set on a Popup object.");
        }

        if ((bool)e.NewValue)
        {
            // if the attached property value is 'true', then enable our trick...
            popup.Opened += Popup_Opened;

            // This is to prevent memory leaks when Popups get removed from the visual tree
            popup.Unloaded += Popup_Unloaded;
        }
        else
        {
            // ... otherwise, disable
            popup.Unloaded -= Popup_Unloaded;
            popup.Opened -= Popup_Opened;
        }      
    }

    private static void Popup_Unloaded(object sender, RoutedEventArgs e)
    {
        // When a Popup is completely unloaded, unsubscribe from everything!
        // This event won't be raised on app's shutdown, but in that case
        // we don't bother with memory leaks anyway.
        Popup p = (Popup)sender;
        p.Unloaded -= Popup_Unloaded;
        p.Opened -= Popup_Opened;      
    }

    private static void Popup_Opened(object sender, EventArgs e)
    {
        Popup p = (Popup)sender;

        // Okay, the Popup is shown. Enable our tricks!
        // First, we determine the window we will monitor:
        Window w = Window.GetWindow(p);
        if (w != null)
        {
            // Then, we need a HwndSource instance of that window
            // to be able to insert our custom Message Hook
            HwndSource source = HwndSource.FromHwnd(new WindowInteropHelper(w).Handle);
            if (source != null)
            {
                // All set, enable our custom window helper!
                WindowHelper.Enable(source, w, p);
            }
        }
    }

    // Our custom helper class. The magic occurs here.
    private class WindowHelper
    {
        private readonly HwndSource mHwndSource;
        private readonly Window mWindow;

        private WindowHelper(HwndSource hwndSource, Window window)
        {
            mHwndSource = hwndSource;
            mWindow = window;
        }

        public static void Enable(HwndSource hwndSource, Window window, Popup popup)
        {
            // Create an instance of our helper class...
            WindowHelper helper = new WindowHelper(hwndSource, window);

            // ... and set a Message Hook to our custom method.
            hwndSource.AddHook(helper.WndProc);

            // Don't forget to disable the magic, when the popup is closed.
            popup.Closed += helper.Popup_Closed;
        }

        private void Popup_Closed(object sender, EventArgs e)
        {
            // The Popup is closed now - disable all!
            Popup p = (Popup)sender;
            p.Closed -= Popup_Closed;
            mHwndSource.RemoveHook(WndProc);
        }

        // This is our custom Windows messages hook.
        // This method will be called whenever our window receives a message.
        private IntPtr WndProc(IntPtr hwnd, int msg, IntPtr wParam, IntPtr lParam, ref bool handled)
        {
            // We're only interested in the WM_SETCURSOR message.
            // It will be sent to our window when the user moves the mouse
            // cursor around and clicks the mouse buttons.
            if (msg != NativeConstants.WM_SETCURSOR)
            {
                return IntPtr.Zero;
            }

            // Determine the necessary parameters.
            // See MSDN topic on WM_SETCURSOR for details.
            var mouseMessage = ((int)lParam & 0xFFFF0000) >> 16;
            var hitTest = (int)lParam & 0xFFFF;

            switch (hitTest)
            {
                // Only continue if the mouse is over
                // 'minimize', 'maximize', 'close'
                case NativeConstants.HTMINBUTTON:
                case NativeConstants.HTMAXBUTTON:
                case NativeConstants.HTCLOSE:
                    break;

                default:
                    // Otherwise, do nothing.
                    return IntPtr.Zero;
            }

            // If the user clicks outside the Popup,
            // a WM_MOUSEMOVE message will be transmitted via WM_SETCURSOR.
            // So if we've received something other - ignore that.
            if (mouseMessage != NativeConstants.WM_MOUSEMOVE)
            {
                return IntPtr.Zero;
            }

            // We need to perform these actions manually,
            // because the window will not receive the corresponding messages
            // on first mouse click (when the Popup is still open).
            switch (hitTest)
            {
                case NativeConstants.HTMINBUTTON:
                    mWindow.WindowState = WindowState.Minimized;
                    break;

                case NativeConstants.HTMAXBUTTON:
                    mWindow.WindowState = WindowState.Maximized;
                    break;

                case NativeConstants.HTCLOSE:
                    mWindow.Close();
                    break;
            }

            // We always return 0, because we don't want any side-effects
            // in the message processing.
            return IntPtr.Zero;
        }
    }

    private static class NativeConstants
    {
        public const int WM_SETCURSOR = 0x020;
        public const int WM_MOUSEMOVE = 0x200;

        public const int HTMINBUTTON = 8;
        public const int HTMAXBUTTON = 9;
        public const int HTCLOSE = 20;
    }
}

希望对您有所帮助！