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c# - Xamarin 社区工具包 TouchEffect.Command 在 CollectionView 中不起作用

问题描述

我正在尝试在 CollectionView 中长按和短按命令。我正在使用 Xamarin.Community.ToolKit 但未调用目标 ViewModel 命令。TouchEffect 在 CollectionView 之外时有效。但不是当它在 CollectionView 内时。

下面是集合视图：

            <CollectionView x:Name="ItemsCollectionView"
                ItemsSource="{Binding FolderFiles}" 
                VerticalOptions="FillAndExpand"
                SelectionMode="{Binding SelectionModeFolderFile}"
                SelectedItems="{Binding SelectedFolderFiles}"
                >
                <CollectionView.ItemTemplate>
                    <DataTemplate>
                        
                        <Grid xct:TouchEffect.Command="{Binding ShortPressCommandSelection}"
                              xct:TouchEffect.LongPressCommand="{Binding LongPressCommandSelection}"
                              xct:TouchEffect.NativeAnimation="True"
                              >
                            <Grid.RowDefinitions>
                                <RowDefinition Height="45"></RowDefinition>
                            </Grid.RowDefinitions>
                            <Grid.ColumnDefinitions>
                                <ColumnDefinition Width="10*"></ColumnDefinition>
                                <ColumnDefinition Width="60*"></ColumnDefinition>
                                <ColumnDefinition Width="10*"></ColumnDefinition>
                                <ColumnDefinition Width="10*"></ColumnDefinition>
                                <ColumnDefinition Width="10*"></ColumnDefinition>
                            </Grid.ColumnDefinitions>


                            <Image Grid.Row="0" Grid.Column="0"  x:Name="imgFileOrFolder" Source="{Binding ImgFileOrFolderSource}"   VerticalOptions="Center" WidthRequest="15" >
                            </Image>

                            <Label Grid.Row="0" VerticalTextAlignment="Center" Grid.Column="1" Text="{Binding Name}" 
                            LineBreakMode="NoWrap" 
                            Style="{DynamicResource ListItemTextStyle}" 
                            FontSize="12" />

                            <Image Grid.Row="0" Grid.Column="2"  x:Name="imgPlay" Source="{Binding ImgPlaySource}"  VerticalOptions="Center" WidthRequest="25">
                                <Image.GestureRecognizers>
                                    <TapGestureRecognizer CommandParameter="{Binding Path}"
                                Tapped="PlayTapped" />
                                </Image.GestureRecognizers>
                            </Image>

                            <Image Grid.Row="0" Grid.Column="3"  x:Name="imgShuffle" Source="{Binding ImgShuffleSource}"  VerticalOptions="Center" WidthRequest="25">
                                <Image.GestureRecognizers>
                                    <TapGestureRecognizer CommandParameter="{Binding Path}"
                                Tapped="ShuffleTapped" />
                                </Image.GestureRecognizers>
                            </Image>

                            <Image Grid.Row="0" Grid.Column="4"  x:Name="imgMoreInfo" Source="{Binding ImgMoreInfoSource}"  VerticalOptions="Center" WidthRequest="15">
                                <Image.GestureRecognizers>
                                    <TapGestureRecognizer
                                Tapped="MoreInfoTapped" />
                                </Image.GestureRecognizers>
                            </Image>
                        </Grid>

                    </DataTemplate>
                </CollectionView.ItemTemplate>
            </CollectionView>

目标视图模型属性：

    public ICommand LongPressCommandSelection { get; set; }

    public ICommand ShortPressCommandSelection { get; set; }

构造函数：

        LongPressCommandSelection = new Command(LongPressCommand_SelectionChanged);
        ShortPressCommandSelection = new Command(ShortPressCommand_SelectionChanged);

方法：

    public void LongPressCommand_SelectionChanged()
    {
        Console.Write("selection changed");

    }

    public void ShortPressCommand_SelectionChanged()
    {
        Console.Write("selection changed");
    }

标签： c#xamarin.formslong-pressxamarin-community-toolkitxamarin.forms.collectionview

解决方案

问题不在于 TouchEffect 问题在于您的 Binding，因为在DataTemplateif BindingContextnot specified 内部会被覆盖（更改）为值 ofItemsSource而不是继承的BindingContext.

您绑定了错误的BindingContext（源），在调试过程中，如果您打开并查看“xaml 绑定失败”窗口/窗格，您将看到明确的明确错误，如LongPressCommandSelection无法在中找到FolderFiles，您应该在此指定您的绑定源案子：

<ContentPage x:Name="thisPage" ...>
...
<Grid xct:TouchEffect.LongPressCommand="{Binding Source={x:Reference thisPage}, Path=BindingContext.LongPressCommandSelection}"

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