WPF ListView 自动选择并获取项目焦点

Question

我不知道如何在 ListView 中自动更改焦点项目。

当我将“IsSelected”属性更改为数据绑定列表中的其他元素时，我希望视图中的焦点项目能够自动更改：

当 PC/SC 读卡器修改项目时（将此视为输入），下一个元素应像这样聚焦：

我想留在 MVVM 中，因此在 ViewModel 中没有引用 View。以下是我当前的代码。

Model ：主要目的是使用 IsSelected 属性扩展 DTO 并实现 INotifyPropertyChanged

public class SmartDeviceModel : INotifyPropertyChanged
{
    public bool IsSelected;
    private DtoReader _dtoReader;

    public SmartDeviceModel(DtoReader _reader)
    {
        _dtoReader = _reader;
    }

    public string DisplayName => _dtoReader.DisplayName;

    public string Uid
    {
        get
        {
            return _dtoReader.Uid;
        }
        set
        {
            _dtoReader.Uid = value;
            OnPropertyChanged("Uid");
        }
    }

    public long RadioId
    {
        get
        {
            return _dtoReader.RadioId : _dtoMarker.RadioId;
        }
        set
        {
            _dtoReader.RadioId = value;
            OnPropertyChanged("RadioId");
        }
    }

    public event PropertyChangedEventHandler PropertyChanged;

    protected void OnPropertyChanged(string name)
    {
        PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(name));
    }
}

ViewModel 收到 PC/SC 读卡器的事件，以将来自 RFID 芯片的数据与当前选定的项目配对。当 RFID 芯片从 PC/SC Reader 中移除时，下一个元素被很好地选择但没有被聚焦。

public class ScanDeviceViewModel : BaseViewModel
{
    public BindingList<SmartDeviceModel> ReaderList { get; }
    public int SelectedReaderIndex;

    private ITagReaderInput _rfidReader;

    public ScanDeviceViewModel()
    {
        //Get Data listener for RFID Tag
        _rfidReader = new IdentivTagReader.IdentivTagReader();
        // Data Source of DTO
        SiteInteractor siteInterractor = new SiteInteractor();

        // List used for DataBinding
        ReaderList = new BindingList<SmartDeviceModel>();

        foreach (DtoReader m in SiteInteractor.GetReaders().OrderBy(x => x.DisplayName))
        {
            ReaderList.Add(new SmartDeviceModel(m));
        }

        if (ReaderList.Count() > 0)
        {
            for (var i = 0; i < ReaderList.Count(); i++)
            {
                if (String.IsNullOrEmpty(ReaderList[i].Uid))
                {
                    SelectedReaderIndex = i;
                    ReaderList[i].IsSelected = true;
                    break;
                }
            }
        }
        _rfidReader.LabelDetected += RfidTagDetected;
        _rfidReader.LabelRemoved += RfidRemoved;
    }

    private void RfidTagDetected(ITagLabel tag)
    {
        if (ReaderList[SelectedReaderIndex] != null && string.IsNullOrEmpty(ReaderList[SelectedReaderIndex].Uid))
        {
            ReaderList[SelectedReaderIndex].IsSelected = true;
            ReaderList[SelectedReaderIndex].Uid = tag.Uid;
            ReaderList[SelectedReaderIndex].RadioId = tag.RadioId;
        }

    }

    private void RfidRemoved(ITagLabel tag)
    {
       if (ReaderList[SelectedReaderIndex].Uid == tag.Uid)
        {
            ReaderList[SelectedReaderIndex].IsSelected = false;
            while (ReaderList.Count >= SelectedReaderIndex + 1)
            {
                SelectedReaderIndex++;
                if (String.IsNullOrEmpty(ReaderList[SelectedReaderIndex].Uid)){
                    ReaderList[SelectedReaderIndex].IsSelected = true;
                    break;
                }
            }
        }
    }
}

查看我正在使用“Setter”，按照here 的建议，将数据绑定到我的模型属性“IsSelected”，但我最想念的还有一些我还不明白的东西。

<ListView ItemsSource="{Binding ReaderList}"  
 Margin="5" x:Name="listViewReader" SelectionMode="Single" 
      <ListView.ItemContainerStyle>
        <Style TargetType="{x:Type ListViewItem}">
           <Setter Property="BorderBrush" Value="LightGray" />
           <Setter Property="BorderThickness" Value="0,0,0,1" />
           <Setter Property="IsSelected" Value="{Binding IsSelected}" />
        </Style>
      </ListView.ItemContainerStyle>
      <ListView.ItemTemplate>
        <DataTemplate>
          <Viewbox Grid.Row ="0" Stretch="Uniform" HorizontalAlignment="Left" VerticalAlignment="Bottom" MaxHeight="90">
              <Grid>
                 <Grid.ColumnDefinitions>
                    <ColumnDefinition Width="*"/>
                    <ColumnDefinition Width="*"/>
                 </Grid.ColumnDefinitions>
                 <Grid.RowDefinitions>
                     <RowDefinition Height="2*" />
                     <RowDefinition Height="*"/>
                 </Grid.RowDefinitions>
                 <Label Content="{Binding DisplayName}" />
                 <DockPanel  Grid.Row="1">
                   <Label Content="UID"/>
                   <Label Content="{Binding Uid}"/>
                 </DockPanel>
                 <DockPanel Grid.Row="1" Grid.Column="1">
                   <Label Content="RadioID" />
                   <Label Content="{Binding RadioId}"/>
                 </DockPanel>
              </Grid>
            </Viewbox>
          </DataTemplate>
    </ListView.ItemTemplate>
</ListView>

我尝试了几种方法like this answer，虽然项目选择得很好，但没有重点。

Answer 1

我终于明白了。以下是我当前的工作代码。

在 Model 中，我刚刚将标志 IsSelected 更改为 IsCurrent 以避免与 ListViewItem 内置属性混淆，但它可能只是一个实现细节。

public class SmartDeviceModel : INotifyPropertyChanged
{
    public bool IsCurrent;
    [...]
}

ViewModel中的BindingList与OP中的大部分相同：

public class ScanDeviceViewModel : INotifyPropertyChanged
{
   public BindingList<SmartDeviceModel> ReaderList { get; internal set; }
   [...]
}

NB : BindingList 似乎减少了 OnNotifyPropertyChange 的需求，但其他类型的 List 应该使用一点点额外的代码。我还注意到 BindingList 可能不适合大型列表场景。

View 使用上面的 ViewModel 作为 DataContext，因此将 ItemSource 绑定到 BindingList。 ListViewItem 样式设置器然后使用模型中的 IsCurrent 属性。

 <ListView ItemsSource="{Binding ReaderList}"  
    SelectionMode="Single"
    SelectionChanged="OnListViewSelectionChanged">
       <ListView.ItemContainerStyle>
              <Style TargetType="{x:Type ListViewItem}">
                   <Setter Property="IsSelected" Value="{Binding IsCurrent}" />
               </Style>
        </ListView.ItemContainerStyle>
 [...]

最后这段View下面的代码主要是根据用户输入模拟焦点，否则elemant被选中但没有焦点，可能超出可见项目范围：

private void OnListViewSelectionChanged(object sender, SelectionChangedEventArgs e)
{
    ListView listView = e.Source as ListView;
    if (listView.ItemContainerGenerator.ContainerFromItem(listView.SelectedItem) is FrameworkElement container)
    {
        container.Focus();
    }
}

Answer 2

根据 MVVM 你可以实现自定义交互行为：

1. 导入到 XAML：xmlns:b="http://schemas.microsoft.com/xaml/behaviors"（如果您使用的是 .NET Core 3.1 - 5）

2. 添加到内容主体：

   <ListView ...>
     <b:Interaction.Behaviors>
       <local:AutoScrollToLastItemBehavior />
     </b:Interaction.Behaviors>
   </ListView>
   

3. 最后添加下一个类：

   public sealed class AutoScrollToLastItemBehavior : Microsoft.Xaml.Behaviors.Behavior<ListView>
   {
   // Need to track whether we've attached to the collection changed event
   bool _collectionChangedSubscribed = false;
   
   protected override void OnAttached()
   {
       base.OnAttached();
       AssociatedObject.SelectionChanged += SelectionChanged;
   
       // The ItemSource of the listView will not be set yet, 
       // so get a method that we can hook up to later
       AssociatedObject.DataContextChanged += DataContextChanged;
   }
   
   private void SelectionChanged(object sender, SelectionChangedEventArgs e)
   {
       ScrollIntoView();
   }
   
   private void CollectionChanged(object sender, NotifyCollectionChangedEventArgs e)
   {
       ScrollIntoView();
   }
   
   private void DataContextChanged(object sender, DependencyPropertyChangedEventArgs e)
   {
       // The ObservableCollection implements the INotifyCollectionChanged interface
       // However, if this is bound to something that doesn't then just don't hook the event
       var collection = AssociatedObject.ItemsSource as INotifyCollectionChanged;
       if (collection != null && !_collectionChangedSubscribed)
       {
           // The data context has been changed, so now hook 
           // into the collection changed event
           collection.CollectionChanged += CollectionChanged;
           _collectionChangedSubscribed = true;
       }
   
   }
   
   private void ScrollIntoView()
   {
       int count = AssociatedObject.Items.Count;
       if (count > 0)
       {
           var last = AssociatedObject.Items[count - 1];
           AssociatedObject.ScrollIntoView(last);
       }
   }
   
   protected override void OnDetaching()
   {
       base.OnDetaching();
       AssociatedObject.SelectionChanged -= SelectionChanged;
       AssociatedObject.DataContextChanged -= DataContextChanged;
   
       // Detach from the collection changed event
       var collection = AssociatedObject.ItemsSource as INotifyCollectionChanged;
       if (collection != null && _collectionChangedSubscribed)
       {
           collection.CollectionChanged -= CollectionChanged;
           _collectionChangedSubscribed = false;
   
       }
   }
   }