Question

我想以编程方式更改FlipView的SelectedIndex。我的ViewModel看起来像这样：

public class MyViewModel : ViewModelBase {
   private int _flipViewIndex;

   public int FlipViewIndex
   {
      get { return _flipViewIndex; }
      private set { Set(ref _flipViewIndex, value); }
   }

   private string _logText;

   public string LogText
   {
      get { return _logText; }
      private set { Set(ref _logText, value); }
   }

   public async void Log(string text)
   {
      CoreDispatcher dispatcher = Windows.ApplicationModel.Core.CoreApplication.MainView.CoreWindow.Dispatcher;
      if (dispatcher.HasThreadAccess)
      {
         LogText += text + "\n";
      }
      else
      {
         await dispatcher.RunAsync(CoreDispatcherPriority.Normal, () => Log(text));
      }
   }

   public async void SetIndex(int index)
   {
      CoreDispatcher dispatcher = Windows.ApplicationModel.Core.CoreApplication.MainView.CoreWindow.Dispatcher;
      if (dispatcher.HasThreadAccess)
      {
         FlipViewIndex = index;
      }
      else
      {
         await dispatcher.RunAsync(CoreDispatcherPriority.Normal, () => SetIndex(index));
      }
   }
}

Set()提出INotifyPropertyChanged.PropertyChanged()。

我的XAML看起来像这样：

<views:BaseView>
 <Grid DataContext="{StaticResource ViewModel}">
  <FlipView SelectedIndex="{Binding FlipViewIndex}">
    <Control1 />
    <Control2 />
    <Control3 />
   </FlipView>
   <TextBlock Text="{Binding LogText}" />
  </Grid>
</views.BaseView>

View和ViewModel似乎绑定正确。当我从控制器中调用ViewModel.Log("foo")时，TextBlock的文本会更新以反映更改。

问题在于，当我致电ViewModel.SetIndex(n)时，FlipView的SelectedIndex无法更新为n，它只会保持为0.任何想法为什么会这样可能会发生什么？

Answer 1

我刚刚确认这是有效的。

<FlipView FontSize="200"
          ItemsSource="{Binding Items}"
          SelectedIndex="{Binding Index, Mode=TwoWay}" />

这样做。

<Page.BottomAppBar>
    <CommandBar>
        <AppBarButton Command="{Binding PrevCommand}"
                      Icon="Previous"
                      Label="Previous" />
        <AppBarButton Command="{Binding NextCommand}"
                      Icon="Next"
                      Label="Next" />
    </CommandBar>
</Page.BottomAppBar>

这个视图模型

public class MyViewModel : BindableBase
{
    public MyViewModel()
    {
        foreach (var item in new[] { 1, 2, 3, 4, 5, 6, 7, 8, 9 })
            this.Items.Add(item);
    }

    ObservableCollection<int> _Items = new ObservableCollection<int>();
    public ObservableCollection<int> Items { get { return _Items; } }

    int _Index = default(int);
    public int Index { get { return _Index; } set { base.SetProperty(ref _Index, value); } }

    public DelegateCommand PrevCommand
    {
        get { return new DelegateCommand(() => { this.Index--; }); }
    }

    public DelegateCommand NextCommand
    {
        get { return new DelegateCommand(() => { this.Index++; }); }
    }
}

作品。真的。

祝你好运！

WinRT FlipView.SelectedIndex绑定未响应ViewModel中的更改

1 个答案: