当 ItemTemplate 有 ScrollViewer 时，Windows Phone 不设置 SelectedItem

Question

我正在使用ReorderListBox control，它允许在列表框中拖放项目。

我还使用MvvmLight、EventTrigger 和EventToCommand 类来捕获Tap 事件并执行RelayCommand 处理程序。当我有一个普通的旧 StackPanel 作为我的列表框的项目模板时，一切正常。但是，只要我将ScrollViewer 插入其中，我的SelectedItem 就会显示为空。有没有办法获取应该绑定到该滚动查看器的项目？代码如下。

视图模型

public ViewModelClass
{
    ...

    public ObservableCollection<MyItemViewModel> MyItemsSource { get; private set; }

    public RelayCommand<MyItemViewModel> EditItemCommand { get; private set; }

    public ViewModelClass()
    {
        EditItemCommand = new RelayCommand<MyItemViewModel>(OnEditItem);
    }

    private void OnEditItem(MyItemViewModel parameter)
    {
        // parameter is always null, even when I change the type of the RelayCommand to object
    }
}

XAML

<rlb:ReorderListBox x:Name="MyListBox" SelectionMode="Single" ItemsSource="{Binding MyItemsSource}" IsReorderEnabled="True">
    <i:Interaction.Triggers>
        <i:EventTrigger EventName="Tap">
            <command:EventToCommand Command="{Binding EditItemCommand}" CommandParameter="{Binding ElementName=MyListBox, Path=SelectedItem}" />
        </i:EventTrigger>
    </i:Interaction.Triggers>
    <rlb:ReorderListBox.ItemTemplate>
        <DataTemplate>
            <ScrollViewer Margin="0,4" toolkit:TiltEffect.IsTiltEnabled="True" HorizontalScrollBarVisibility="Auto" VerticalScrollBarVisibility="Disabled">
                <StackPanel Orientation="Horizontal">
                    <TextBlock Text="{Binding SomeProperty}" Style="{StaticResource BaseTextStyle}" FontSize="{StaticResource PhoneFontSizeMediumLarge}" FontFamily="Segoe WP SemiLight" VerticalAlignment="Center" />
                    <Border Background="DarkGoldenrod" Margin="3" VerticalAlignment="Center">
                        <TextBlock Margin="6,3" Text="{Binding AnotherProperty}" Foreground="White" FontFamily="Segoe WP Light" FontSize="16" VerticalAlignment="Center" TextAlignment="Right" />
                    </Border>
                </StackPanel>
            </ScrollViewer>
        </DataTemplate>
    </rlb:ReorderListBox.ItemTemplate>
</rlb:ReorderListBox>

Answer 1

试试看：

<rlb:ReorderListBox x:Name="MyListBox" SelectionMode="Single" 
                           ItemsSource="{Binding MyItemsSource}" 
                           IsReorderEnabled="True"
                           Height="400">
<i:Interaction.Triggers>
    <i:EventTrigger EventName="Tap">
        <command:EventToCommand Command="{Binding EditItemCommand}" CommandParameter="{Binding ElementName=MyListBox, Path=SelectedItem}" />
    </i:EventTrigger>
</i:Interaction.Triggers>
<rlb:ReorderListBox.Template>
    <ControlTemplate>
        <ScrollViewer Margin="0,4" toolkit:TiltEffect.IsTiltEnabled="True" HorizontalScrollBarVisibility="Auto" VerticalScrollBarVisibility="Auto">
            <ItemsPresenter />
        </ScrollViewer>
    </ControlTemplate>
</rlb:ReorderListBox.Template>
<rlb:ReorderListBox.ItemTemplate>
    <DataTemplate>
        <StackPanel Orientation="Horizontal">
            <TextBlock Text="{Binding SomeProperty}" FontSize="{StaticResource PhoneFontSizeMediumLarge}" FontFamily="Segoe WP SemiLight" VerticalAlignment="Center" />
            <Border Background="DarkGoldenrod" Margin="3" VerticalAlignment="Center">
                <TextBlock Margin="6,3" Text="{Binding AnotherProperty}" Foreground="White" FontFamily="Segoe WP Light" FontSize="16" VerticalAlignment="Center" TextAlignment="Right" />
            </Border>
        </StackPanel>
    </DataTemplate>
</rlb:ReorderListBox.ItemTemplate>

高度在这里很重要，因为您需要指定它才能使 ScrollViewer 正常工作。

但是，这使得选择工作有点糟糕？就像选择了多个项目一样...我不知道是控制本身的错误还是什么。

我会尝试使用 SelectionChanged 事件而不是 Tap 并在此处获取真实选择的项目，然后对其进行处理。