更新的答案 - 05/11

Question

我在WPF中发现WindowsFormsHost的一个非常奇怪的行为。我发现如果一个WPF控件没有WindowsFormsHost作为子控件，那么IsKeyboardFocusWithinChanged fires properly - 只要WPF控件获得或失去焦点，就会触发它，并且变量{ {1}}按预期切换（当控件获得焦点时IsKeyboardFocusWithin，失去焦点时true。

但是，如果我在WPF中托管false，那么片刻之后，WPF母控件和WindowsFormHost子控件都不再触发IsKeyboardFocusWithinChanged事件。

我在MSDN文档中找不到或为什么这样，有什么原因？

这是我的代码：

MainWindow.xaml

WindowsFormHost

MainWindow.xaml.cs

<Window x:Class="WpfApplication1.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
        xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
        xmlns:local="clr-namespace:WpfApplication1"
        mc:Ignorable="d"
        Title="MainWindow" Height="350" Width="525" IsKeyboardFocusWithinChanged="Window_IsKeyboardFocusWithinChanged">
    <Grid Name="grid1">
    </Grid>
</Window>

当涉及public partial class MainWindow : Window { public MainWindow() { InitializeComponent(); host = new System.Windows.Forms.Integration.WindowsFormsHost(); var mtbDate = new System.Windows.Forms.MaskedTextBox("00/00/0000"); host.Child = mtbDate; host.IsKeyboardFocusWithinChanged += Host_IsKeyboardFocusWithinChanged; grid1.Children.Add(host); } private void Host_IsKeyboardFocusWithinChanged(object sender, DependencyPropertyChangedEventArgs e) { Console.WriteLine(host.IsKeyboardFocusWithin.ToString()+" blah"); } private System.Windows.Forms.Integration.WindowsFormsHost host; private void Window_IsKeyboardFocusWithinChanged(object sender, DependencyPropertyChangedEventArgs e) { Console.WriteLine(IsKeyboardFocusWithin.ToString()); } }的行被注释掉时，只要控件获得焦点，WindowsFormHost就是IsKeyboardFocusWithin，而当控件失去焦点时，true就会被false。

当包含WindowsFormHost的行时，IsKeyboardFocusWithin为true，直到我点击该控件，然后host.IsKeyboardFocusWithin变为false，并且IsKeyboardFocusWithin也变为false，然后，无论我做什么，IsKeyboardFocusWithinChanged事件都不会再被触发。

Answer 1

更新的答案 - 05/11

优化以前的解决方案，以支持WindowsFormsHost中的多个Window元素。此外，如果IsKeyboardFocusWithin属性为true，则更新样式以突出显示具有绿色边框的聚焦控件。

<强> MainWindow.xaml

<Window x:Class="WpfApplication1.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
        xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
        xmlns:local="clr-namespace:WpfApplication1"
        mc:Ignorable="d"
        Title="MainWindow" Height="250" Width="325">
    <Window.Resources>
        <ResourceDictionary>
            <Style TargetType="Border">
                <Setter Property="BorderThickness" Value="2" />
                <Setter Property="BorderBrush" Value="Transparent" />
                <Style.Triggers>
                    <DataTrigger Binding="{Binding RelativeSource={RelativeSource Self}, Path=Child.IsKeyboardFocusWithin}" Value="True">
                        <Setter Property="BorderBrush" Value="Green" />
                    </DataTrigger>
                </Style.Triggers>
            </Style>
        </ResourceDictionary>
    </Window.Resources>
    <Grid>
        <Grid.ColumnDefinitions>
            <ColumnDefinition />
            <ColumnDefinition />
        </Grid.ColumnDefinitions>
        <Button x:Name="hiddenBtn" Height="1" Width="1" />
        <StackPanel Grid.Column="0" x:Name="leftPanel" Margin="5">
            <Label HorizontalContentAlignment="Right">Start Date</Label>
            <Label HorizontalContentAlignment="Right">End Date</Label>
            <Label HorizontalContentAlignment="Right">Phone Number</Label>
            <Label HorizontalContentAlignment="Right">Zip Code</Label>
        </StackPanel>
        <StackPanel Grid.Column="1" x:Name="rightPanel" Margin="5">

        </StackPanel>
    </Grid>
</Window>

<强> MainWindow.xaml.cs

public partial class MainWindow : Window
{
    public MainWindow()
    {
        InitializeComponent();

        GenerateControls();
    }

    protected override void OnSourceInitialized(EventArgs e)
    {
        base.OnSourceInitialized(e);

        HwndSource source = PresentationSource.FromVisual(this) as HwndSource;
        source.AddHook(WndProc);
    }

    private const int WM_KILLFOCUS = 0x0008;
    private const int WM_ACTIVATEAPP = 0x001c;
    private const int WM_PARAM_FALSE = 0x00000000;

    private IntPtr WndProc(IntPtr hwnd, int msg, IntPtr wParam, IntPtr lParam, ref bool handled)
    {
        // Handle messages...
        if (msg == WM_KILLFOCUS)
        {
            Console.WriteLine(wParam + " " + lParam);
            //suppress kill focus message if host has keyboardfocus, else don't
            var hosts = FindVisualChildren<WindowsFormsHost>(this);
            var focusedControlHwnd = wParam.ToInt32();
            if(focusedControlHwnd != 0)
            {
                handled = hosts.Any(x => x.Child.Handle.ToInt32() == focusedControlHwnd);
            }
        }
        else if (msg == WM_ACTIVATEAPP && wParam.ToInt32() == WM_PARAM_FALSE)
        {
            //now the kill focus could be suppressed event during window switch, which we want to avoid
            //so we make sure that the host control property is updated 
            var hosts = FindVisualChildren<WindowsFormsHost>(this);
            if (hosts.Any(x => x.IsKeyboardFocusWithin))
                hiddenBtn.Focus();
        }

        return IntPtr.Zero;
    }

    private void GenerateControls()
    {
        System.Windows.Forms.MaskedTextBox maskedTextBox;
        System.Windows.Forms.Integration.WindowsFormsHost host;

        host = new System.Windows.Forms.Integration.WindowsFormsHost();
        maskedTextBox = new System.Windows.Forms.MaskedTextBox("00/00/0000");
        host.Child = maskedTextBox;
        rightPanel.Children.Add(new Border() { Child = host });

        host = new System.Windows.Forms.Integration.WindowsFormsHost();
        maskedTextBox = new System.Windows.Forms.MaskedTextBox("00/00/0000");
        host.Child = maskedTextBox;
        rightPanel.Children.Add(new Border() { Child = host });

        host = new System.Windows.Forms.Integration.WindowsFormsHost();
        maskedTextBox = new System.Windows.Forms.MaskedTextBox("(000)-000-0000");
        host.Child = maskedTextBox;
        rightPanel.Children.Add(new Border() { Child = host });

        host = new System.Windows.Forms.Integration.WindowsFormsHost();
        maskedTextBox = new System.Windows.Forms.MaskedTextBox("00000");
        host.Child = maskedTextBox;
        rightPanel.Children.Add(new Border() { Child = host });
    }

    public static IEnumerable<T> FindVisualChildren<T>(DependencyObject depObj) where T : DependencyObject
    {
        if (depObj != null)
        {
            for (int i = 0; i < VisualTreeHelper.GetChildrenCount(depObj); i++)
            {
                DependencyObject child = VisualTreeHelper.GetChild(depObj, i);
                if (child != null && child is T)
                {
                    yield return (T)child;
                }

                foreach (T childOfChild in FindVisualChildren<T>(child))
                {
                    yield return childOfChild;
                }
            }
        }
    }
}

<强>截图

上一个答案 - 05/05

正如Hans Passant在评论中提到的，这种行为是由于WindowsFormsHost和MaskedTextBox具有不同的Hwnd（s）而引起的。

第一次单击主机控件时，子控件将获得焦点，并且正确设置了IsKeyboardFocusedWithin。但是一旦子控件获得焦点，操作系统就会注意到Hwnd的差异并将kill-focus消息发送到WPF窗口 - 这反过来又将IsKeyboardFocusedWithin设置为false。

您可以做的是在WPF主窗口中添加WndProc挂钩，并禁止kill-focus消息 - 仅当主机控件的IsKeyboardFocusedWithin值为true时。

但是，有一个副作用 - 当您从WPF窗口切换时，主机控件的IsKeyboardFocusedWithin值可能保持为真。为了解决这个问题，您可以使用简单的遍历技巧在发送窗口禁用消息时移动焦点，从而根据当前状态更新属性IsKeyboardFocusedWithin。

源代码示例： 我使用StackPanel而不是Grid，以显示TextBox

public partial class MainWindow : Window
{
    public MainWindow()
    {
        InitializeComponent();

        host = new System.Windows.Forms.Integration.WindowsFormsHost();
        var mtbDate = new System.Windows.Forms.MaskedTextBox("00/00/0000");
        host.Child = mtbDate;
        host.IsKeyboardFocusWithinChanged += Host_IsKeyboardFocusWithinChanged;
        stackPanel1.Children.Add(host);

        textBox1 = new TextBox();
        stackPanel1.Children.Add(textBox1);

        textBox2 = new TextBox();
        stackPanel1.Children.Add(textBox2);
    }

    private void Host_IsKeyboardFocusWithinChanged(object sender, DependencyPropertyChangedEventArgs e)
    {
        Console.WriteLine(host.IsKeyboardFocusWithin.ToString() + " blah");
        textBox1.Text = $"Host.IsKeyboardFocusedWithin = {host.IsKeyboardFocusWithin}";
    }

    private System.Windows.Forms.Integration.WindowsFormsHost host;
    private TextBox textBox1;
    private TextBox textBox2;

    private void Window_IsKeyboardFocusWithinChanged(object sender, DependencyPropertyChangedEventArgs e)
    {
        Console.WriteLine(IsKeyboardFocusWithin.ToString());
        textBox2.Text = $"Window.IsKeyboardFocusedWithin = {IsKeyboardFocusWithin}";
    }

    protected override void OnSourceInitialized(EventArgs e)
    {
        base.OnSourceInitialized(e);

        HwndSource source = PresentationSource.FromVisual(this) as HwndSource;
        source.AddHook(WndProc);
    }

    private const int WM_KILLFOCUS = 0x0008;
    private const int WM_ACTIVATEAPP = 0x001c;
    private const int WM_PARAM_FALSE = 0x00000000;

    private IntPtr WndProc(IntPtr hwnd, int msg, IntPtr wParam, IntPtr lParam, ref bool handled)
    {
        // Handle messages...
        if (msg == WM_KILLFOCUS) 
        {
            //suppress kill focus message if host has keyboardfocus, else don't
            handled = host.IsKeyboardFocusWithin;
        }
        else if (msg == WM_ACTIVATEAPP && wParam.ToInt32() == WM_PARAM_FALSE)
        {
            //now the kill focus could be suppressed event during window switch, which we want to avoid
            //so we make sure that the host control property is updated by traversal (or any other method)
            if (host.IsKeyboardFocusWithin)
            {
                host.MoveFocus(new TraversalRequest(FocusNavigationDirection.Next));
            }
        }

        return IntPtr.Zero;
    }
}

而且，结果将如下所示：

有焦点

无焦点

WindowsFormsHost的存在导致IsKeyboardFocusWithinChanged最多被触发两次而不是更多

1 个答案:

更新的答案 - 05/11

上一个答案 - 05/05