Beahvior

Question

我在ListView MultiSelection中遇到问题。

这是我的代码：

   private ICommand _excludeCurveCommand;


    public ICommand ExcludeCurveCommand
    {
        get
        {
            if (_excludeCurveCommand == null)
                _excludeCurveCommand = new DelegateCommand<object>(param => this.ExcludeCurveExecuted(param));

            return _excludeCurveCommand;
        }
    }

    /// <summary>
    /// Executed event for ContextMenu --> Remove click
    /// </summary>
    /// <param name="param">param is FolderItemViewModel bound as CommandParameter</param>
    private void ExcludeCurveExecuted(object param)
    {

        ICollection<object> curves = param as ICollection<object>;
        int count =  curves.Count;
    }



 < Button Content="Exclude" Command="{Binding ExcludeCurveCommand}" CommandParameter="{Binding SelectedItems,ElementName=lstView}" .../>

< ListView Name="lstView"  ItemsSource="{Binding MyList}" SelectionMode="Extended" ..../>

这里我使用了shift并从前四项中选择。但是在ExcludeCurveExecuted方法中，我总是得到一些随机数。这有什么问题。

修改 *我不想在ViewModel中使用IsSelected标志

Answer 1

对我来说，似乎您启用了ListView UI虚拟化，因为它默认启用。这意味着，ListView仅绘制UI上可见的项目。

以下是MSDN link

为了确定接口上的内容（例如您的选择）我恐怕您没有其他选择

或禁用UI虚拟化（不好）
或在ModelView上实现IsSelected标志

祝你好运。

Answer 2

您可以使用行为将所选项目同步到视图模型中的集合....

您需要在项目中添加对System.Windows.Interactivity的引用以及Xaml中的别名

Beahvior

public class MultiSelectionBehavior : Behavior<ListView>
    {
        protected override void OnAttached()
        {
            base.OnAttached();
            if (SelectedItems != null)
            {
                AssociatedObject.SelectedItems.Clear();
                foreach (var item in SelectedItems)
                {
                    AssociatedObject.SelectedItems.Add(item);
                }
            }
        }

public IList SelectedItems
{
    get { return (IList)GetValue(SelectedItemsProperty); }
    set { SetValue(SelectedItemsProperty, value); }
}

public static readonly DependencyProperty SelectedItemsProperty =
    DependencyProperty.Register("SelectedItems", typeof(IList), typeof(MultiSelectionBehavior), new UIPropertyMetadata(null, SelectedItemsChanged));

private static void SelectedItemsChanged(DependencyObject o, DependencyPropertyChangedEventArgs e)
{
    var behavior = o as MultiSelectionBehavior;
    if (behavior == null)
        return;

    var oldValue = e.OldValue as INotifyCollectionChanged;
    var newValue = e.NewValue as INotifyCollectionChanged;

    if (oldValue != null)
    {
        oldValue.CollectionChanged -= behavior.SourceCollectionChanged;
        behavior.AssociatedObject.SelectionChanged -= behavior.ListViewSelectionChanged;
    }
    if (newValue != null)
    {
        behavior.AssociatedObject.SelectedItems.Clear();
        foreach (var item in (IEnumerable)newValue)
        {
            behavior.AssociatedObject.SelectedItems.Add(item);
        }

        behavior.AssociatedObject.SelectionChanged += behavior.ListViewSelectionChanged;
        newValue.CollectionChanged += behavior.SourceCollectionChanged;
    }
}

private bool _isUpdatingTarget;
private bool _isUpdatingSource;

void SourceCollectionChanged(object sender, NotifyCollectionChangedEventArgs e)
{
    if (_isUpdatingSource)
        return;

    try
    {
        _isUpdatingTarget = true;

        if (e.OldItems != null)
        {
            foreach (var item in e.OldItems)
            {
                AssociatedObject.SelectedItems.Remove(item);
            }
        }

        if (e.NewItems != null)
        {
            foreach (var item in e.NewItems)
            {
                AssociatedObject.SelectedItems.Add(item);
            }
        }
    }
    finally
    {
        _isUpdatingTarget = false;
    }
}

private void ListViewSelectionChanged(object sender, SelectionChangedEventArgs e)
{
    if (_isUpdatingTarget)
        return;

    var selectedItems = this.SelectedItems;
    if (selectedItems == null)
        return;

    try
    {
        _isUpdatingSource = true;

        foreach (var item in e.RemovedItems)
        {
            selectedItems.Remove(item);
        }

        foreach (var item in e.AddedItems)
        {
            selectedItems.Add(item);
        }
    }
    finally
    {
        _isUpdatingSource = false;
    }
}

}

的Xaml

    <ListView ItemsSource="{Binding ItemsList}"
             DisplayMemberPath="Name"
             SelectionMode="Extended">
        <i:Interaction.Behaviors>
            <local:MultiSelectionBehavior SelectedItems="{Binding MySelectedItems}" />
        </i:Interaction.Behaviors>
    </ListView>

MySelectedItems是ViewModel中的集合

不要忘记它在ViewModel中初始化... MySelectedItems ....

您的ViewModel

private void ExcludeCurveExecuted(object param)
{                  
    int count =  MySelectedItems.Count;
}

MultiSelection在ListView中不起作用

2 个答案:

Beahvior

的Xaml

您的ViewModel