[英]WPF: Command on listbox item context menu / menu item does not work even though it does on a button
我有一個自定義的RoutedUICommand,當綁定到按鈕的Command屬性時,它可以正常工作。 但是,當綁定到列表框項目上的ConextMenu MenuItem時,它將不起作用。 CanExecute方法不會被調用,因此該項目在上下文菜單中保持禁用狀態。 但是,CanExecute是從按鈕的綁定中調用的。
在下面的回購示例中, CrawlCommands.AddCredit
是命令。 它綁定到按鈕和ListBoxItems。 Button的行為符合預期,但ListBoxItem卻沒有。 右鍵單擊列表框項確實會顯示上下文菜單,並且菜單項的標題正確地偏離了Command,但是CanExecute從不被調用,因此它永遠不知道該命令有效,因此保持禁用狀態。
我想念什么?
<UserControl x:Class="CrawlSpace.TestCommands"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
xmlns:local="clr-namespace:CrawlSpace"
mc:Ignorable="d"
d:DesignHeight="300" d:DesignWidth="300" Background="#FF020523">
<UserControl.CommandBindings>
<CommandBinding Command="local:CrawlCommands.AddCredit" Executed="ExecutedAddCredit" CanExecute="CanExecuteAddCredit"/>
</UserControl.CommandBindings>
<Grid>
<Grid.Resources>
<local:MockData x:Key="TestData"/>
</Grid.Resources>
<Grid.Background>
<SolidColorBrush Color="DarkGray"/>
</Grid.Background>
<Grid.RowDefinitions>
<RowDefinition Height="7*"/>
<RowDefinition Height="3*"/>
</Grid.RowDefinitions>
<!-- A button with a command, this one works! -->
<Button x:Name="button" Command="local:CrawlCommands.AddCredit" Content="Add Credit" Margin="10" Grid.Row="1" Width="177"/>
<ListBox x:Name="listBox" Margin="10" Background="LightBlue" ItemsSource="{StaticResource TestData}">
<ListBox.Resources>
<!-- Define a context menu -->
<ContextMenu x:Key="ItemMenu">
<MenuItem Command="local:CrawlCommands.AddCreditBlock"/>
</ContextMenu>
<!-- Sets a context menu for each ListBoxItem in the current ListBox -->
<Style TargetType="{x:Type ListBoxItem}">
<!-- This menu item will not function even though the button verison above does -->
<Setter Property="ContextMenu" Value="{StaticResource ItemMenu}"></Setter>
</Style>
</ListBox.Resources>
<ListBox.ItemTemplate>
<DataTemplate>
<StackPanel Orientation="Horizontal">
<TextBlock Text="{Binding FirstName}"/>
</StackPanel>
</DataTemplate>
</ListBox.ItemTemplate>
</ListBox>
</Grid>
請參閱我的代碼。 對我來說很好。
<UserControl x:Class="DragDrop_Learning.UserControl1"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
mc:Ignorable="d"
xmlns:local="clr-namespace:DragDrop_Learning"
d:DesignHeight="300" d:DesignWidth="300">
<UserControl.CommandBindings>
<CommandBinding Command="local:CrawlCommands.AddCredit" Executed="ExecutedAddCredit" CanExecute="CanExecuteAddCredit"/>
<CommandBinding Command="local:CrawlCommands.AddCreditBlock" Executed="ExecutedAddCreditBlock" CanExecute="CanExecuteAddCreditBlock"/>
</UserControl.CommandBindings>
<Grid>
<Grid.Resources>
</Grid.Resources>
<Grid.Background>
<SolidColorBrush Color="DarkGray"/>
</Grid.Background>
<Grid.RowDefinitions>
<RowDefinition Height="7*"/>
<RowDefinition Height="3*"/>
</Grid.RowDefinitions>
<!-- A button with a command, this one works! -->
<Button x:Name="button" Command="local:CrawlCommands.AddCredit" Content="Add Credit" Margin="10" Grid.Row="1" Width="177"/>
<ListBox x:Name="listBox" Margin="10" Background="LightBlue" >
<ListBox.Resources>
<!-- Define a context menu -->
<ContextMenu x:Key="ItemMenu">
<MenuItem Command="local:CrawlCommands.AddCreditBlock"/>
</ContextMenu>
<!-- Sets a context menu for each ListBoxItem in the current ListBox -->
<Style TargetType="{x:Type ListBoxItem}">
<!-- This menu item will not function even though the button verison above does -->
<Setter Property="ContextMenu" Value="{StaticResource ItemMenu}"></Setter>
</Style>
</ListBox.Resources>
<ListBox.ItemTemplate>
<DataTemplate>
<StackPanel Orientation="Horizontal">
<TextBlock Text="{Binding FirstName}"/>
</StackPanel>
</DataTemplate>
</ListBox.ItemTemplate>
</ListBox>
</Grid>
public partial class UserControl1 : UserControl
{
public UserControl1()
{
InitializeComponent();
List<Person> lst = new List<Person>();
listBox.ItemsSource = lst;
lst.Add(new Person() { FirstName="Test"});
}
private void CanExecuteAddCredit(object sender, CanExecuteRoutedEventArgs e)
{
e.CanExecute = true;
}
private void ExecutedAddCredit(object sender, ExecutedRoutedEventArgs e)
{
}
private void CanExecuteAddCreditBlock(object sender, CanExecuteRoutedEventArgs e)
{
e.CanExecute = true;
}
private void ExecutedAddCreditBlock(object sender, ExecutedRoutedEventArgs e)
{
}
}
public static class CrawlCommands
{
public static readonly RoutedUICommand AddCredit = new RoutedUICommand
(
"AddCredit",
"AddCredit",
typeof(CrawlCommands)
);
public static readonly RoutedUICommand AddCreditBlock = new RoutedUICommand
(
"AddCreditBlock",
"AddCreditBlock",
typeof(CrawlCommands)
);
}
class Person
{
private string myVar;
public string FirstName
{
get { return myVar; }
set { myVar = value; }
}
}
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