Windows Phone 8绑定多个选择ListView

2 回答

• 0

  我也面临着这个问题 . 当我试图在转换器中更改选择模式时，它的工作方式与预期不符 . 我发现的任何解决方法都是使用多选模式，但在添加/删除项目的CollectionChanged事件中操作 . 例如，如果我需要单一选择模式，我将选择重写为新选择的项目 .

  像这样的东西：

  private void OnSelectedPlayersChanged(object sender, NotifyCollectionChangedEventArgs e)
  {
          if (e.Action == NotifyCollectionChangedAction.Add)
          {
              if (this.SelectionMode == Mode.Once)
              {
                  SynchronizationContextProvider.UIThreadSyncContext.Post((d) =>
                  {
                      this.SelectedPlayers.Clear();
                      this.SelectedPlayers.Add((Players)e.NewItems[0]);
                  }, null);
              }
          }
  
          if (e.Action == NotifyCollectionChangedAction.Remove)
          {
              //some logic
          }
  }
  

  这是迄今为止我发现的最佳选择 . 如果你能找到更好的东西，我会乐意使用它 .

  回复于 2024-04-29T01:14:08+08:00
• 1

  我最终解决了我希望看到但仍然不完美的问题 . 我最终创建了ListView的子类，并添加了两个属性SelectedItems2和SelectionMode2 . 如果有人可以帮助调整以下代码，以便我可以重用SelectedItems和SelectionMode，这将使解决方案更接近完美 .

  子类代码

  /// <summary>
  /// Enhanced List View
  /// 
  /// SeletionMode Switching:
  /// This class enhances ListView to support changing the selection mode from None/Single to Multiple and back and having it
  /// bind the selected items without forgetting them when changing selection mode.  The base ListView will remove the selected items when switching
  /// from Multiple SelectionMode to another SelectionMode.
  /// 1) Created SelectedItems2 to bind to View Model as SelectedItems will have items removed and SelectedItems is not easy to bind to SelectedItems.
  /// 2) On SelectionChanged, remember the selected items in SelectedItems2 how the user selected or unselected them.
  /// 3) On SelectionMode set to Multiple, fill the underlying SelectedItems with the values from SelectedItems2 so that the checkboxes are checked on the ListView.
  /// 4) Use _isMergingItems flag to ignore selection changed events being fired by merging of the SelectedItem2 and SelectedItems2 collections.
  /// 
  /// Doesn't support changing SelectedItems2 bound collection while in Multiple SelectionMode yet.
  /// To do so we would need to hook the CollectionChanged event on the SelectedItems2 List object that is bound.
  /// and likely handle threading issues with the merging of SelectedItems and SelectedItems2.
  /// </summary>
  public class MyListView : ListView
  {
      private bool _isMergingItems;
  
      public MyListView()
      {
          SelectionChanged += MyListView_SelectionChanged;
      }
  
      private void MyListView_SelectionChanged(object sender, SelectionChangedEventArgs e)
      {
          // Ignore selection changed event when selection mode is not multiple.
          // This is mainly here because when changing from Multiple to Single, this event is fired and will cause
          // the items to be removed from SelectedItems2 which is not what is desired.
          if (SelectionMode != ListViewSelectionMode.Multiple) { return; }
          if (_isMergingItems) { return; }
  
          try
          {
              _isMergingItems = true;
  
              var selectedItems2List = SelectedItems2 as IList;
              if (selectedItems2List == null) { return; }
  
              foreach (var itemToAdd in e.AddedItems)
              {
                  selectedItems2List.Add(itemToAdd);
              }
  
              foreach (var itemToRemove in e.RemovedItems)
              {
                  selectedItems2List.Remove(itemToRemove);
              }
          }
          finally
          {
              _isMergingItems = false;
          }
      }
  
      #region --- Dependency Properties ---
  
      private static readonly DependencyProperty SelectionMode2Property = DependencyProperty.Register("SelectionMode2", typeof(ListViewSelectionMode), typeof(MyListView), new PropertyMetadata(ListViewSelectionMode.None, SelectionMode2Changed));
  
      public ListViewSelectionMode SelectionMode2
      {
          get { return (ListViewSelectionMode)GetValue(SelectionMode2Property); }
          set { SetValue(SelectionMode2Property, value); }
      }
  
      private static void SelectionMode2Changed(DependencyObject d, DependencyPropertyChangedEventArgs e)
      {
  
          var listView = d as MyListView;
          var value = (ListViewSelectionMode)e.NewValue;
  
          // Set the underlying selection mode property to cause the control to 
          // change to and from Multiple selection mode.
          listView.SelectionMode = value;
  
          // When Multiple selction mode, we will need to load the underlying SelectedItems of the ListView
          // so that the checkboxes are checked appropriatly.  When the selection mode is changed the underlying ListView
          // removes the selected items.
          if (value == ListViewSelectionMode.Multiple)
          {
              listView.FillUnderlyingSelectedItems();
          }
      }
  
      private static readonly DependencyProperty SelectedItems2Property = DependencyProperty.Register("SelectedItems2", typeof(object), typeof(MyListView), null);
  
      /// <summary>
      /// SelectedItems2 is used as the property to bind the selected items to the ViewModel.
      /// Using a List as the data type did not seem to work for binding.  Since ItemSource is an object on the base class
      /// object was chosen for this property as well.
      /// 
      /// However, SelectedItems2 will need to bind to IList in order for it to work properly.
      /// </summary>
      public object SelectedItems2
      {
          get { return (object)GetValue(SelectedItems2Property); }
          set { SetValue(SelectedItems2Property, value); }
      }
  
      #endregion
  
      private void FillUnderlyingSelectedItems()
      {
          var selectedItems2List = SelectedItems2 as IList;
          if (selectedItems2List == null) { return; }
  
          try
          {
              _isMergingItems = true;
  
              foreach (var item in selectedItems2List)
              {
                  SelectedItems.Add(item);
              }
          }
          finally
          {
              _isMergingItems = false;
          }
      }
  }
  

  用途：XAML

  <localUI:MyListView ItemsSource="{Binding Roster}"
            SelectedItems2="{Binding SelectedPlayers}"
            SelectionMode2="{Binding IsEditingGameRoster, Converter={StaticResource ListViewSelectionModeFromBooleanNoneOrMultipleConverter}}">
      <ListView.ItemTemplate>
          <DataTemplate>
              <!-- List View Display  Not important for describing problem. -->
          </DataTemplate>
      </ListView.ItemTemplate>
  </localUI:MyListView>
  

  用法：ViewModel

  private ObservableCollection<Player> _selectedPlayers;
  
      public ObservableCollection<Player> SelectedPlayers
      {
          get
          {
              if (_selectedPlayers == null)
              {
                  _selectedPlayers = new ObservableCollection<Player>();
              }
  
              return _selectedPlayers;
          }
      }
  

  回复于 2024-04-29T01:14:08+08:00