WPF routed command enabling works with menu but not with a button

问题

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>

回答1:

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!

来源：https://stackoverflow.com/questions/10683574/wpf-routed-command-enabling-works-with-menu-but-not-with-a-button

标签

wpf

command