如何解决Xamarin 社区工具包 TouchEffect.Command 在 CollectionView 中不起作用
我正在尝试在 CollectionView 中执行长按和短按命令。我正在使用 Xamarin.Community.ToolKit 但没有调用目标 viewmodel 命令。 TouchEffect 在 CollectionView 之外时有效。但不是当它在 CollectionView 中时。
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");
}
解决方法
问题不在于 TouchEffect 问题在于您的绑定,因为在 DataTemplate
中,如果未指定 BindingContext
将被覆盖(更改)为 ItemsSource
的值而不是继承了BindingContext
。
您绑定了错误的 BindingContext
(源代码),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,说明 LongPressCommandSelection
可以在 FolderFiles
中找不到,在这种情况下您应该指定您的绑定源:
<ContentPage x:Name="thisPage" ...>
...
<Grid xct:TouchEffect.LongPressCommand="{Binding Source={x:Reference thisPage},Path=BindingContext.LongPressCommandSelection}"
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