Question

我正在使用Windows Phone Control工具包中的ContextMenu。想知道如何知道按下列表中的哪个列表项？似乎我可以知道选择了哪个上下文菜单，但我无法知道操作哪个列表项。请帮忙。谢谢！

        <DataTemplate x:Key="ListItemTemplate">
            <StackPanel Grid.Column="1" VerticalAlignment="Top">
                <TextBlock Tag="{Binding Index}"  Text="{Binding SName}" TextWrapping="Wrap" Style="{StaticResource PhoneTextExtraLargeStyle}" />
              <toolkit:ContextMenuService.ContextMenu>
                <toolkit:ContextMenu>
                  <toolkit:MenuItem Header="Add to playlist" Click="Move_Click"/>
                </toolkit:ContextMenu>
              </toolkit:ContextMenuService.ContextMenu>
            </StackPanel>

        private void Move_Click(object sender, RoutedEventArgs e)
    {
        String name = (string)((MenuItem)sender).Header;
        // how to know which index of the item is targeted on
    }

Answer 1

我也会推荐MVVM，但它可以简化。无需为每个对象设置ViewModel。关键是将命令绑定到ItemsControl的DataContext（例如ListBox）。

假设您的ItemTemplate用于ListBox，ListBox将其ItemsSource属性绑定到ViewModel。你的xaml看起来像这样：

<ListBox x:Name="SongsListBox" ItemsSource="{Binding Songs}">
    <ListBox.ItemTemplate>
        <DataTemplate >
            <StackPanel >
                <TextBlock Text="{Binding SName}" TextWrapping="Wrap" Style="{StaticResource PhoneTextExtraLargeStyle}" />
                <toolkit:ContextMenuService.ContextMenu>
                   <toolkit:ContextMenu>
                       <toolkit:MenuItem Header="Add to playlist" Command="{Binding DataContext.AddToPlaylistCommand, ElementName=SongsListBox}" CommandParameter="{Binding}"/>
                   </toolkit:ContextMenu>
                </toolkit:ContextMenuService.ContextMenu>
            </StackPanel>              
        </DataTemplate>
    </ListBox.ItemTemplate>
</ListBox>

您的ViewModel将具有属性Songs，该属性是模型对象的集合。它还有一个ICommand AddToPlaylistCommand。正如我said before，我最喜欢的ICommand实现是来自PNP团队的DelegateCommand。

public class ViewModel : INotifyPropertyChanged
{
    public ViewModel()
    {
        Songs = new ObservableCollection<Songs>();
        AddToPlaylistCommand = new DelegateCommand<Song>(AddToPlaylist);
    }
    public ICollection<Songs> Songs { get; set; }
    public ICommand AddToPlaylistCommand  { get; private set; }

    private void AddToPlaylist(Song song)
    {
        // I have full access to my model!
        // add the item to the playlist
    }

    // Other stuff for INotifyPropertyChanged
}

Answer 2

答案是：MVVM。不要在代码隐藏中使用事件注册，而是在ViewModel中调用命令。首先，不是绑定到Data对象，而是绑定到ViewModel（或者表示单个列表项的ViewModel，如果您在列表中）。然后，让ViewModel公开一个可以直接在数据绑定VM上调用的Command，而不是使用Click事件。

以下是我的United Nations News OSS WP7应用中的简化示例：（XAML，C#）

<DataTemplate x:Key="ArticleItemDataTemplate">
    <StackPanel>
        <toolkit:ContextMenuService.ContextMenu>
            <toolkit:ContextMenu>
                <toolkit:MenuItem Command="{Binding NavigateToArticle}" Header="read article"/>
                <toolkit:MenuItem Command="{Binding ShareViaEmail}" Header="share via email"/>
                <toolkit:MenuItem Command="{Binding ShareOnFacebook}" Header="share on facebook"/>
                <toolkit:MenuItem Command="{Binding ShareOnTwitter}" Header="share on twitter"/>
            </toolkit:ContextMenu>
        </toolkit:ContextMenuService.ContextMenu>
        <TextBlockText="{Binding Title}">
    </StackPanel>
</DataTemplate>

public ICommand ShareOnTwitter
{
    get
    {
        return new RelayCommand(() => 
            IoC.Get<ISocialShareService>().ShareOnTwitter(ShareableOnSocialNetwroks));
    }
}

public ICommand ShareOnFacebook
{
    get
    {
        return new RelayCommand(() =>
            IoC.Get<ISocialShareService>().ShareOnFacebook(ShareableOnSocialNetwroks));
    }
}

public ICommand ShareViaEmail
{
    get
    {
        return new RelayCommand(() =>
            IoC.Get<ISocialShareService>().ShareViaEmail(ShareableOnSocialNetwroks));
    }
}

这是我在Neurons WP7 OSS项目中使用的同一个想法的另一个简化示例：（XAML，C#）

    <DataTemplate x:Key="YouTubeVideoItem">
        <Grid>
            <Button >
                <toolkit:ContextMenuService.ContextMenu>
                    <toolkit:ContextMenu IsZoomEnabled="False">
                        <toolkit:MenuItem Command="{Binding NavigateToVideo}" Header="play video" />
                        <toolkit:MenuItem Command="{Binding ViewInBrowser}" Header="open in browser" />
                        <toolkit:MenuItem Command="{Binding SendInEmail}" Header="share via email" />
                        <toolkit:MenuItem Command="{Binding FacebookInBrowser}" Header="share on facebook" />
                        <toolkit:MenuItem Command="{Binding TweetInBrowser}" Header="share on twitter" />
                    </toolkit:ContextMenu>
                </toolkit:ContextMenuService.ContextMenu>
                <Custom:Interaction.Triggers>
                    <Custom:EventTrigger EventName="Click">
                        <GalaSoft_MvvmLight_Command:EventToCommand Command="{Binding NavigateToVideo}"/>
                    </Custom:EventTrigger>
                </Custom:Interaction.Triggers>
                <StackPanel Orientation="Horizontal">
                    <Image Height="90" Source="{Binding ImageUrl}" />
                    <TextBlock Width="271" Text="{Binding Title}" />
                </StackPanel>
            </Button>
        </Grid>
    </DataTemplate>

    public ICommand ViewInBrowser
    {
        get
        {
            return new RelayCommand(() =>
                TaskInvoker.OpenWebBrowser(this.ExternalLink.OriginalString)
            );
        }
    }

    public ICommand TweetInBrowser
    {
        get
        {
            return new RelayCommand(() =>
                IoC.Get<IMessenger>().Send(new NavigateToMessage(PageSources.WebBrowser, TwitterUri)));
        }
    }

    public ICommand FacebookInBrowser
    {
        get
        {
            return new RelayCommand(() =>
                IoC.Get<IMessenger>().Send(new NavigateToMessage(PageSources.WebBrowser, FacebookUri)));
        }
    }

如何使上下文菜单适用于Windows Phone？

2 个答案: