更改DataContext不会更新列表字段

2 回答

• 0

  在您的示例中， SelectedItem 是否有两个属性 Title 和 Items ？或者 Items 是您的viewmodel中的属性？如果答案是后者，那么你可以在下面找到解决方案 .

  我不试试看 . 如果您的意思是未设置自定义控件上的 ItemsSource ，则必须将 XAML 指向正确的方向 . 如果这是您想要实现的目标，您可以在下面找到解决方案 . 我所做的是用这行代码将编译器指向正确的源代码：

  ItemsSource="{Binding DataContext.Items, RelativeSource={RelativeSource AncestorType=Window}}"
  

  在这里，您说编译器可以在窗口的 DataContext （或任何可以找到 property 的控件）中找到 Binding property .

  <StackPanel>
          <ListBox x:Name="TheList" ItemsSource="{Binding Items}" SelectedItem="{Binding SelectedItem}">
              <ListBox.ItemTemplate>
                  <DataTemplate>
                      <TextBlock Text="{Binding Title}"/>
                  </DataTemplate>
              </ListBox.ItemTemplate>
          </ListBox>
          <StackPanel DataContext="{Binding ElementName=TheList, Path=SelectedItem}">
              <TextBlock Text="{Binding Title}" FontSize="20"/>
              <local:MultiTypeDynamicTextBlock ItemsSource="{Binding DataContext.Items, RelativeSource={RelativeSource AncestorType=Window}}"/>
          </StackPanel>
      </StackPanel>
  

  希望这有帮助 .

  ---

  EDIT

  当我从 ListBox 中选择另一个时， title property 会发生变化 . 如果 Items 设置为新的 ObservableCollection ，当 SelectedItem 更改时，是否为 Items 调用 OnPropertyChanged event ？

  OnPropertyChanged("Items");
  

  回复于 2024-05-06T00:55:49+08:00
• 0

  谢谢您的帮助 . 我设法通过更新MultiTypeDynamicTextBlock来解决这个问题，如下所示：

  public class MultiTypeDynamicTextBlock : TextBlock
  {
      public interface ISection
      {
          Inline GetDisplayElement();
  
          ISection Clone();
      }
  
      public class TextOption : ISection
      {
          private Run mText;
  
          public TextOption(string aText)
          {
              mText = new Run();
              mText.Text = aText.Replace("\\n", "\n");
          }
  
          public Inline GetDisplayElement()
          {
              return mText;
          }
  
          public ISection Clone()
          {
              return new TextOption(mText.Text);
          }
      }
  
      public class LineBreakOption : ISection
      {
          public Inline GetDisplayElement()
          {
              return new LineBreak();
          }
  
          public ISection Clone()
          {
              return new LineBreakOption();
          }
      }
  
      public class SectionList
      {
          private ObservableCollection<ISection> mList;
  
          public Action CollectionChanged;
  
          public ObservableCollection<ISection> Items
          {
              get
              {
                  ObservableCollection<ISection> lRet = new ObservableCollection<ISection>();
                  foreach (ISection lCurr in mList)
                  {
                      lRet.Add(lCurr.Clone());
                  }
                  return lRet;
              }
          }
  
          public int Count { get { return mList.Count; } }
  
          public SectionList()
          {
              mList = new ObservableCollection<ISection>();
          }
  
          public void Add(ISection aValue)
          {
              mList.Add(aValue);
          }
  
          public SectionList Clone()
          {
              SectionList lRet = new SectionList();
              lRet.mList = Items;
              return lRet;
          }
      }
  
      public MultiTypeDynamicTextBlock()
      {
  
      }
  
      public static readonly DependencyProperty ItemsCollectionProperty =
          DependencyProperty.Register("ItemsCollection", typeof(SectionList), typeof(MultiTypeDynamicTextBlock),
              new UIPropertyMetadata((PropertyChangedCallback)((sender, args) =>
              {
                  MultiTypeDynamicTextBlock textBlock = sender as MultiTypeDynamicTextBlock;
                  SectionList inlines = args.NewValue as SectionList;
  
                  if (textBlock != null)
                  {
                      if ((inlines != null) && (inlines.Count > 0))
                      {
                          textBlock.ItemsCollection.CollectionChanged += textBlock.ResetInlines;
                          textBlock.Inlines.Clear();
                          foreach (ISection lCurr in textBlock.ItemsCollection.Items)
                          {
                              textBlock.Inlines.Add(lCurr.GetDisplayElement());
                          }
                      }
                      else
                      {
                          inlines = new SectionList();
                          inlines.Add(new TextOption("No value set"));
                          textBlock.ItemsCollection = inlines;
                      }
                  }
              })));
  
      public SectionList ItemsCollection
      {
          get
          {
              return (SectionList)GetValue(ItemsCollectionProperty);
          }
          set
          {
              SectionList lTemp;
              if (value == null)
              {
                  lTemp = new SectionList();
                  lTemp.Add(new TextOption("No value set for property"));
              }
              else
              {
                  lTemp = value;
              }
              SetValue(ItemsCollectionProperty, lTemp);
          }
      }
  
      private void ResetInlines()
      {
          Inlines.Clear();
          foreach (ISection lCurr in ItemsCollection.Items)
          {
              Inlines.Add(lCurr.GetDisplayElement());
          }
      }
  }
  

  并且我将Binded的字段更新为MultiTypeDynamicTextBlock.SectionList类型

  只要我使用副本（克隆）它正在工作，由于某种原因，当我不克隆它从列表中的显示删除值，如果有人知道为什么我会喜欢学习但我设法绕过它 . 窗口的XAML是：

  <StackPanel>
      <ListBox x:Name="TheList" ItemsSource="{Binding GeneralItems}" SelectedItem="{Binding SelectedItem}">
          <ListBox.ItemTemplate>
              <DataTemplate>
                  <StackPanel>
                      <TextBlock Text="{Binding Title}" FontSize="20"/>
                      <local:MultiTypeDynamicTextBlock ItemsCollection="{Binding Items}" Margin="20,0,0,0"/>
                  </StackPanel>
              </DataTemplate>
          </ListBox.ItemTemplate>
      </ListBox>
      <StackPanel DataContext="{Binding GeneralItems, Path=SelectedItem}">
          <TextBlock Text="{Binding Title}" FontSize="20"/>
          <local:MultiTypeDynamicTextBlock DataContext="{Binding Items}" ItemsCollection="{Binding}" Margin="20,0,0,0"/>
      </StackPanel>
  </StackPanel>
  

  回复于 2024-05-06T00:55:49+08:00