WPF路由命令启用与菜单，但不与按钮 [英] WPF routed command enabling works with menu but not with a button

问题描述

在以下示例中，当文本接收到焦点而不是按钮时，将启用菜单。我已经尝试了只是按钮和文本框，但行为是一样的。

 < Window x：Class = WpfPopup.MainWindow
 xmlns =http://schemas.microsoft.com/winfx/2006/xaml/presentation
 xmlns：x =http://schemas.microsoft.com/winfx / 2006 / xaml
 Title =MainWindowHeight =350Width =525> 
< DockPanel> 
< Menu DockPanel.Dock =Top> 
< MenuItem Command =ApplicationCommands.Paste/> 
< / Menu> 
< TextBox BorderBrush =BlackBorderThickness =2Margin =25TextWrapping =Wrapx：Name =text1Height =58Width =203> 
 MenuItem将不会被启用，直到
此TextBox获取键盘焦点
< / TextBox> 
< Button Content =ButtonHeight =23Name =button1Width =93Command =ApplicationCommands.Paste/> 
< / DockPanel> 
  

解决方案>

有两种简单的解决方法：

1）使用FocusManager.IsFocusScope：

 < Button Content =ButtonHeight =23Name =button1Width =93Command =ApplicationCommands.PasteFocusManager.IsFocusScope =True/& 
  

2）手动设置按钮上的CommandTarget：

 < Button Content =ButtonHeight =23Name =button1Width =93Command =ApplicationCommands.PasteCommandTarget ={Binding ElementName = text1}/> 
  

您可能想知道为什么这适用于菜单项？如果您阅读了 FocusManager.IsFocusScope attach的属性你会得到答案：

默认情况下，Window类是一个焦点范围，菜单，
ContextMenu和ToolBar类。一个作为焦点范围的元素
将IsFocusScope设置为true。

当你不知道的时候很混乱！

In the following example the menu is enabled when the text receives the focus but not the button. I have tried it with just the button and the text box but the behaviour is the same.

<Window x:Class="WpfPopup.MainWindow"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    Title="MainWindow" Height="350" Width="525">
<DockPanel>
    <Menu DockPanel.Dock="Top">
        <MenuItem  Command="ApplicationCommands.Paste" />
    </Menu>
    <TextBox BorderBrush="Black" BorderThickness="2" Margin="25" TextWrapping="Wrap" x:Name="text1" Height="58" Width="203" >
        The MenuItem will not be enabled until
        this TextBox gets keyboard focus
    </TextBox>        
    <Button Content="Button" Height="23" Name="button1" Width="93" Command="ApplicationCommands.Paste" />
</DockPanel>

解决方案

There are two simple ways to fix this:

1) Use FocusManager.IsFocusScope:

    <Button Content="Button" Height="23" Name="button1" Width="93" Command="ApplicationCommands.Paste" FocusManager.IsFocusScope="True"/>

2) Set the CommandTarget on the button manually:

<Button Content="Button" Height="23" Name="button1" Width="93" Command="ApplicationCommands.Paste" CommandTarget="{Binding ElementName=text1}" />

You are probably wondering why this works for the menu item? If you read the documentation for FocusManager.IsFocusScope attached property you will get the answer:

By default, the Window class is a focus scope as are the Menu, ContextMenu, and ToolBar classes. An element which is a focus scope has IsFocusScope set to true.

Very confusing when you don't know that!

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