虚拟化堆栈面板MVVM +多重选择

发布于 2024-12-05 03:49:24 字数 796 浏览 2 评论 0原文

我已经实现了一种类似于这篇文章中描述的选择模式，使用 ViewModel 来存储 IsSelected 值，并将 ListViewItem.IsSelected 绑定到 ViewModel IsSelected：

<ListView.ItemContainerStyle>
    <Style TargetType="{x:Type ListViewItem}">
        <Setter Property="IsSelected" Value="{Binding Mode=TwoWay, Path=IsSelected}"/>
    </Style>
</ListView.ItemContainerStyle>

它通常可以工作，但我遇到了一个严重的问题。通过使用 VirtualizingStackPanel 作为列表视图中的面板，仅创建可见的 ListViewItem。如果我使用“Ctrl+A”选择所有项目，或者在第一个项目上使用“Shift+Ctrl+End”等快捷组合，则所有项目都会被选中，但对于不可见的项目，ViewModel 不会获取其 IsSelected设置为 true。这是合乎逻辑的，因为如果未创建 ListViewItem，绑定就无法工作。

有人遇到过同样的问题，并找到了解决方案（除了不使用 VirtualizingStackPanel 之外）？

原文

I have implemented a selection pattern similar to the one described in this post using a ViewModel to store the IsSelected value, and by binding the ListViewItem.IsSelected to the ViewModel IsSelected:

<ListView.ItemContainerStyle>
    <Style TargetType="{x:Type ListViewItem}">
        <Setter Property="IsSelected" Value="{Binding Mode=TwoWay, Path=IsSelected}"/>
    </Style>
</ListView.ItemContainerStyle>

It works in general, but I encounter a severe problem. By using the a VirtualizingStackPanel as the panel in the list view, only the visible ListViewItem are getting created. If I use "Ctrl+A" to select all items, or by using shortcut combination such "Shift+Ctrl+End" on the first item, all items get selected, but for the non visible items, the ViewModel does not get its IsSelected set to true. That is logical, because if the ListViewItem are not created, the binding can't work.

Anybody experienced the same issue, and found a solution (apart from not using a VirtualizingStackPanel)?

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扭转时空 2024-12-12 03:49:24

我在 MVVM 模式中找到了另一种处理选择的方法，它解决了我的问题。不是在视图模型中维护选择，而是从 ListView/ListBox 中检索选择，并将其作为参数传递给命令。一切都在 XAML 中完成：

<ListView 
    x:Name="_items"
    ItemsSource="{Binding Items}" ... />

<Button 
    Content="Remove Selected" 
    Command="{Binding RemoveSelectedItemsCommand}" 
    CommandParameter="{Binding ElementName=_items, Path=SelectedItems}"/>

在我的 ViewModel 中：

private void RemoveSelection(object parameter)
{
    IList selection = (IList)parameter;
    ...
}

I found another way of handling selection in the MVVM pattern, which solved my issue. Instead of maintaining the selection in the viewmodel, the selection is retrieved from the ListView/ListBox, and passed as a parameter to the Command. All done in XAML:

<ListView 
    x:Name="_items"
    ItemsSource="{Binding Items}" ... />

<Button 
    Content="Remove Selected" 
    Command="{Binding RemoveSelectedItemsCommand}" 
    CommandParameter="{Binding ElementName=_items, Path=SelectedItems}"/>

in my ViewModel:

private void RemoveSelection(object parameter)
{
    IList selection = (IList)parameter;
    ...
}

回复收藏 0 原文

甜妞爱困 2024-12-12 03:49:24

就我而言，我最终通过从 ListBox 派生 ListBoxEx 类并添加代码来响应选择更改、在项目视图模型上强制选择状态来解决此问题：

private readonly List<IListItemViewModelBase> selectedItems = new List<IListItemViewModelBase>();

protected override void OnSelectionChanged(SelectionChangedEventArgs e)
{
    base.OnSelectionChanged(e);

    bool isVirtualizing = VirtualizingStackPanel.GetIsVirtualizing(this);
    bool isMultiSelect = (SelectionMode != SelectionMode.Single);

    if (isVirtualizing && isMultiSelect)
    {
        var newSelectedItems = SelectedItems.Cast<IListItemViewModelBase>();

        foreach (var deselectedItem in this.selectedItems.Except(newSelectedItems))
        {
            deselectedItem.IsSelected = false;
        }

        this.selectedItems.Clear();
        this.selectedItems.AddRange(newSelectedItems);

        foreach (var newlySelectedItem in this.selectedItems)
        {
            newlySelectedItem.IsSelected = true;
        }
    }
}

In my case, I ended up solving this by deriving a ListBoxEx class from ListBox, and adding code to respond to selection changes, enforcing the selection state on the item view models:

private readonly List<IListItemViewModelBase> selectedItems = new List<IListItemViewModelBase>();

protected override void OnSelectionChanged(SelectionChangedEventArgs e)
{
    base.OnSelectionChanged(e);

    bool isVirtualizing = VirtualizingStackPanel.GetIsVirtualizing(this);
    bool isMultiSelect = (SelectionMode != SelectionMode.Single);

    if (isVirtualizing && isMultiSelect)
    {
        var newSelectedItems = SelectedItems.Cast<IListItemViewModelBase>();

        foreach (var deselectedItem in this.selectedItems.Except(newSelectedItems))
        {
            deselectedItem.IsSelected = false;
        }

        this.selectedItems.Clear();
        this.selectedItems.AddRange(newSelectedItems);

        foreach (var newlySelectedItem in this.selectedItems)
        {
            newlySelectedItem.IsSelected = true;
        }
    }
}

回复收藏 0 原文

吻泪 2024-12-12 03:49:24

除了不使用 VirtualizingStackPanel 之外，我唯一能想到的就是捕获这些键盘快捷键并提供修改特定范围的 ViewModel 项的方法，以便它们的 >IsSelected 属性设置为True（例如，SelectAll()、SelectFromCurrentToEnd()）。基本上绕过 ListViewItem 上的 Binding 来控制此类情况的选择。