我正在制作一个 winodws 8 手机应用程序，并试图从 Windows Phone 工具包中获得一个上下文菜单。
我一直在关注本教程，但我使用的是内置于 WP8 中的长列表选择器，而不是列表框
<DataTemplate x:Key="GroceryListItemTemplate">
<StackPanel Grid.Column="1" Grid.Row="1">
<TextBlock x:Name="tbName" TextWrapping="Wrap" Text="{Binding Name}" FontSize="32"/>
<TextBlock x:Name="tbProductInfo" TextWrapping="Wrap" Text="{Binding ProductInfoLabel}" HorizontalAlignment="Left"/>
</StackPanel>
<toolkit:ContextMenuService.ContextMenu>
<toolkit:ContextMenu>
<toolkit:MenuItem Header="Edit"
Command="{Binding GroceryItemsVm.EditGroceryItemCmd, Source={StaticResource Locator}}"
CommandParameter="{Binding}"/>
<toolkit:MenuItem Header="Delete" Command="{Binding GroceryItemsVm.DeleteGroceryItemCmd, Source={StaticResource Locator}}"
CommandParameter="{Binding}"/>
</toolkit:ContextMenu>
</toolkit:ContextMenuService.ContextMenu>
</DataTemplate>
以上是我的代码的精简版
这是我的列表选择器
<phone:LongListSelector IsGroupingEnabled="True" ItemsSource="{Binding GroceryItems}" HideEmptyGroups="True" LayoutMode="List" Grid.Row="1">
<phone:LongListSelector.ItemTemplate>
<StaticResource ResourceKey="GroceryListItemTemplate"/>
</phone:LongListSelector.ItemTemplate>
</phone:LongListSelector>
这是我的 mvvm 代码
public class GroceryItemsVm : ViewModelBase
{
public GroceryItemsVm()
{
if (IsInDesignMode)
{
}
else
{
EditGroceryItemCmd = new RelayCommand<GroceryItem>(this.Edit);
DeleteGroceryItemCmd = new RelayCommand<GroceryItem>(this.Delete);
GroceryItems = // method that gets all items back as grouped.
}
}
private List<Group<GroceryItem>> groceryItems = null;
/// <summary>
/// Sets and gets the GroceryItems property.
/// Changes to that property's value raise the PropertyChanged event.
/// </summary>
public List<Group<GroceryItem>> GroceryItems
{
get
{
return groceryItems;
}
set
{
if (groceryItems == value)
{
return;
}
RaisePropertyChanging(() => GroceryItems);
groceryItems = value;
RaisePropertyChanged(() => GroceryItems);
}
}
private async void Delete(GroceryItem obj)
{
// trigged on context delete
}
private void Edit(GroceryItem obj)
{
// triggered on context edit
}
public RelayCommand<GroceryItem> EditGroceryItemCmd
{
get;
private set;
}
public RelayCommand<GroceryItem> DeleteGroceryItemCmd
{
get;
private set;
}
}
public class GroceryItem : ObservableObject
{
/// <summary>
/// The <see cref="Name" /> property's name.
/// </summary>
public const string NamePropertyName = "Name";
private string name = "";
/// <summary>
/// Sets and gets the Name property.
/// Changes to that property's value raise the PropertyChanged event.
/// </summary>
public string Name
{
get
{
return name;
}
set
{
if (name == value)
{
return;
}
RaisePropertyChanging(() => Name);
name = value;
RaisePropertyChanged(() => Name);
}
}
}
现在当我运行它时，它第一次工作，无论我选择编辑它的任何项目，都会得到正确的对象。但是，下一个对象将始终相同。选择完成后它永远不会改变它的选择。
编辑
这是一个例子。
- 运行
- 触发上下文菜单以显示超过“1”
- 点击编辑 - 注意对话框消息（会说 1）
- 点击“返回按钮”
- 触发上下文菜单以显示超过“3”
- 点击编辑 - 注意对话框消息（会说 3）
我唯一能想到的就是覆盖我要访问的页面的后退按钮，然后导航到该页面。这有点愚蠢，但这就是我能想到的。
public partial class MvvmView1 : PhoneApplicationPage
{
// Constructor
public MvvmView1()
{
InitializeComponent();
// Sample code to localize the ApplicationBar
//BuildLocalizedApplicationBar();
}
private void Button_Click(object sender, RoutedEventArgs e)
{
NavigationService.GoBack();
}
protected override void OnBackKeyPress(CancelEventArgs e)
{
NavigationService.Navigate(new Uri("/MainPage.xaml", UriKind.Relative));
}
}