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c# - 当焦点位于 WindowsFormsHost 内时,为什么 Keyboard.FocusedElement 为空?它打破了 WPF 命令路由

转载 作者:太空狗 更新时间:2023-10-29 23:46:20 24 4
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我有一个自定义 RoutedUICommand MyCommand 通过 ICommand.Execute 执行.顶部窗口有一个绑定(bind)来处理它:

<Window.CommandBindings>
<CommandBinding Command="local:MainWindow.MyCommand" CanExecute="CanExecuteCommmand" Executed="CommandExecuted"/>
</Window.CommandBindings>

这是此命令的唯一处理程序。我还有一个 WindowsFormsHost内部带有 WinForms 的 TextBox 控件(用于演示目的)。 当焦点在此 TextBox 内时,MyCommand 不会到达顶部窗口。当焦点位于 WPF 的 native TextBox 内时,命令处理程序按预期被调用。

我发现这是因为Keyboard.FocusedElement当焦点位于 WindowsFormsHost 内时为 null。为什么在这种情况下它是 null,是 WPF 错误还是设计功能?我错过了什么吗?

我相信命令应该到达顶部窗口,无论焦点在哪里(当它是可视化树中唯一的处理程序并且 FocusManager.IsFocusScope 设置正确时)。我有一个 related question about that .

项目源可用here .

XAML:

<Window x:Class="WpfCommandTest.MainWindow"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:local="clr-namespace:WpfCommandTest"
xmlns:wf="clr-namespace:System.Windows.Forms;assembly=System.Windows.Forms"
Title="MainWindow" Height="480" Width="640" Background="Gray">

<Window.CommandBindings>
<CommandBinding Command="local:MainWindow.MyCommand" CanExecute="CanExecuteCommmand" Executed="CommandExecuted"/>
</Window.CommandBindings>

<StackPanel Margin="20,20,20,20">
<TextBox Name="textBoxOutput" Focusable="True" IsTabStop="True" Height="150" Text="WPF TextBox&#x0a;"/>
<WindowsFormsHost Focusable="True" KeyboardNavigation.IsTabStop="True" Height="150">
<wf:TextBox x:Name="textBoxWf" Text="WinForms TextBox" />
</WindowsFormsHost>
<Button FocusManager.IsFocusScope="True" Name="btnTest" Focusable="False" IsTabStop="False" Content="Test (ICommand.Execute)" Click="btnTest_Click" Width="200"/>
<Button FocusManager.IsFocusScope="True" Focusable="False" IsTabStop="False" Content="Test (Command property)" Command="local:MainWindow.MyCommand" Width="200"/>
<Button FocusManager.IsFocusScope="True" Name="btnClearFocus" Focusable="False" IsTabStop="False" Content="Clear Focus" Click="btnClearFocus_Click" Width="200"/>
</StackPanel>

</Window>

C#:

using System;
using System.Windows;
using System.Windows.Input;

namespace WpfCommandTest
{
public partial class MainWindow : Window
{
public static readonly RoutedUICommand MyCommand = new RoutedUICommand("MyCommand", "MyCommand", typeof(MainWindow));
const string Null = "null";

public MainWindow()
{
InitializeComponent();
this.Loaded += (s, e) => textBoxOutput.Focus(); // set focus on the TextBox
}

void CanExecuteCommmand(object sender, CanExecuteRoutedEventArgs e)
{
e.CanExecute = true;
}

void CommandExecuted(object sender, ExecutedRoutedEventArgs e)
{
var routedCommand = e.Command as RoutedCommand;
var commandName = routedCommand != null ? routedCommand.Name : Null;
Log("*** Executed: {0} ***, {1}", commandName, FormatFocus());
}

void btnTest_Click(object sender, RoutedEventArgs e)
{
Log("btnTest_Click, {0}", FormatFocus());
ICommand command = MyCommand;
if (command.CanExecute(null))
command.Execute(null);
}

void btnClearFocus_Click(object sender, RoutedEventArgs e)
{
FocusManager.SetFocusedElement(this, this);
Keyboard.ClearFocus();
Log("btnClearFocus_Click, {0}", FormatFocus());
}

void Log(string format, params object[] args)
{
textBoxOutput.AppendText(String.Format(format, args) + Environment.NewLine);
textBoxOutput.CaretIndex = textBoxOutput.Text.Length;
textBoxOutput.ScrollToEnd();
}

string FormatType(object obj)
{
return obj != null ? obj.GetType().Name : Null;
}

string FormatFocus()
{
return String.Format("focus: {0}, keyboard focus: {1}",
FormatType(FocusManager.GetFocusedElement(this)),
FormatType(Keyboard.FocusedElement));
}
}
}

最佳答案

要完成互操作 Form-WPF,您需要执行以下操作:

App.xaml.cs:

    public partial class App : Application
{
protected override void OnStartup(StartupEventArgs e)
{
WindowsFormsHost.EnableWindowsFormsInterop();
base.OnStartup(e);
}
}

关于c# - 当焦点位于 WindowsFormsHost 内时,为什么 Keyboard.FocusedElement 为空?它打破了 WPF 命令路由,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/18437898/

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