CommandParameter дает нулевое значение при использовании DataTemplate для списка в формах xamarin

Question

Я столкнулся с проблемой в CommandParameter, который находится в DataTemplate для listView.У меня есть отдельный DataTemplate для ListView, и я не могу передать путь к изображению в commandParameter при нажатии на изображение в listView.

 <?xml version="1.0" encoding="utf-8" ?>

xmlns: local = "clr-namespace: RCBazaar.Localization" xmlns:template = "clr-namespace: RCBazaar.Views.Templates" xmlns: cards = "clr-namespace: PanCardView; Assembly = PanCardView" xmlns: controls = "clr-namespace: PanCardView.Controls; Assembly = PanCardView" x: Class = "RCBazaar.Views.HomeView "Padding =" 0 "x: Name =" HomePage "> ->

<ContentPage.Content>

    <Grid  Style="{StaticResource MainGrid}">
        <Grid.RowDefinitions>
            <RowDefinition  Height="140"></RowDefinition>
            <RowDefinition  Height="Auto"></RowDefinition>
            <RowDefinition  Height="*"  ></RowDefinition>
        </Grid.RowDefinitions>

        <cards:CarouselView  Margin="0"  x:Name="carousel" Grid.Row="0"  ItemsSource="{Binding ProductImage,Mode=TwoWay}" >
            <cards:CarouselView.ItemTemplate>
                <DataTemplate>
                    <ffimageloading:CachedImage HorizontalOptions="FillAndExpand" Source="{Binding ImageName}" Style="{StaticResource CachedImageStyle}">
                    </ffimageloading:CachedImage>
                </DataTemplate>
            </cards:CarouselView.ItemTemplate>
            <controls:IndicatorsControl ToFadeDuration="1500"  BackgroundColor="Gray"/>
            <controls:LeftArrowControl  ToFadeDuration="2500" BackgroundColor="Gray" />
            <controls:RightArrowControl ToFadeDuration="2500" BackgroundColor="Gray"/>
        </cards:CarouselView>



        <Image Grid.Row="1" Margin="0,0,10,0" Source="ic_sort.png" HeightRequest="30" WidthRequest="30"  HorizontalOptions="EndAndExpand">
            <Image.GestureRecognizers>
                <TapGestureRecognizer Command="{Binding SortPopupCommand}"/>
            </Image.GestureRecognizers>
        </Image>

        <ListView IsEnabled="True"  HeightRequest="{Binding ListHeight}"  CachingStrategy="RecycleElement" x:Name="mylist" Style="{StaticResource ListviewStyle}" Grid.Row="2" SelectedItem="{Binding SelectedProduct,Mode=TwoWay}"  ItemsSource="{Binding HomeProducts}" >
            <ListView.Behaviors>
                <behaviors:EventToCommandBehavior EventName="ItemSelected"   Command="{Binding HomeProductSelectedCommand}"></behaviors:EventToCommandBehavior>
            </ListView.Behaviors>
            <ListView.ItemTemplate>
                <DataTemplate>
                    <template:ProductCell ParentBindingContext="{Binding Source={x:Reference mylist}, Path=BindingContext}"/>

                </DataTemplate>
            </ListView.ItemTemplate>
        </ListView>


        <ActivityIndicator Grid.Row="2"  VerticalOptions="Start"   IsVisible="{Binding IsBusy,Mode=TwoWay}" IsRunning="{Binding IsBusy,Mode=TwoWay}" Color="Blue"/>

    </Grid>

</ContentPage.Content>

ProductCell

<ViewCell.View>
    <Grid   RowSpacing="5" Style="{StaticResource ProductTemplateGrid}"  >
        <Grid.RowDefinitions>
            <RowDefinition Height="28*"/>
            <RowDefinition Height="Auto"/>
            <RowDefinition Height="Auto"/>
            <RowDefinition Height="Auto"/>
            <RowDefinition Height="Auto"/>
        </Grid.RowDefinitions>
        <Grid.ColumnDefinitions>
            <ColumnDefinition Width="40*"/>
            <ColumnDefinition Width="60*"/>
        </Grid.ColumnDefinitions>

        <ffimageloading:CachedImage  x:Name="img" VerticalOptions="FillAndExpand" Style="{StaticResource CachedImageStyle}" Aspect="AspectFit"  Grid.Row="0" Source="{Binding PictureBinary,Converter={StaticResource Base64StringToImageConverter}}" Grid.RowSpan="5" Grid.Column="0">
            <ffimageloading:CachedImage.GestureRecognizers>

                <TapGestureRecognizer BindingContext="{Binding Source={x:Reference mylist}, Path=ParentBindingContext}" Command="{Binding ViewImageCommand}" CommandParameter="{Binding PictureBinary}"/>
            </ffimageloading:CachedImage.GestureRecognizers>
        </ffimageloading:CachedImage>


        <Label Grid.Row="0"  Grid.Column="1" MaxLines="2" LineBreakMode="TailTruncation"  Style="{StaticResource lblDarkBody}"  Text="{Binding Name}" ></Label>

        <Label Grid.Row="1" Grid.Column="1" Text="{local:Translate SKU}" Style="{StaticResource lblNormal}"></Label>
        <Label Margin="35,0,0,0" Grid.Row="1" Grid.Column="1" Text="{Binding upc}" Style="{StaticResource lblNormal}"    />

        <Label Grid.Row="2" Grid.Column="1" Text="{local:Translate Stock}"  Style="{StaticResource lblNormal}" VerticalOptions="Center" ></Label>
        <Image Margin="45,0,0,0" Grid.Row="2" Grid.Column="1" VerticalOptions="Center" HorizontalOptions="StartAndExpand" Source="{Binding qtyonhand,Converter={StaticResource QuantityToColorConverter}}" />

        <uc:CustomRatingBar  Grid.Row="3" Grid.Column="1"  Style="{StaticResource RatingsStyle}"     x:Name="CusRatingBar"  Rating="{Binding RatingSum}" />

        <Image Grid.Row="4" Grid.Column="1"  Source="in.png" HorizontalOptions="Start" VerticalOptions="Center"/>
        <Label Margin="30,0,0,0"  Grid.Row="4" Grid.Column="1" VerticalOptions="Center" Style="{StaticResource lblEmphasis}"  Text="{Binding pricelist,StringFormat='Rs {0:#,0.#0}'}" ></Label>

        <Image Grid.Row="4" Grid.Column="1" Margin="0,0,10,0" WidthRequest="30" HeightRequest="30" VerticalOptions="Center"  Style="{StaticResource StockCachedImageStyle}"  Source="heartdark.png"  HorizontalOptions="End">

            <Image.GestureRecognizers>
                <TapGestureRecognizer BindingContext="{Binding Source={x:Reference mylist}, Path=ParentBindingContext}"  Command="{Binding AddtoWishlistCommand}" CommandParameter="{Binding .}" />
            </Image.GestureRecognizers>
        </Image>

    </Grid>
</ViewCell.View>

Answer 1

Если вы задаете для рассматриваемой страницы x:Name в своем XAML, вы можете ссылаться на исходный BindingContext (должен быть вашим ViewModel), одновременно имея доступ к самому элементу как BindingContext для параметра команды.Выглядит примерно так:

<ContentPage x:Name="MyContentPage"
....
<!--inside your DataTemple you can now reference the BindingContext of your page-->
Command="{Binding Path=BindingContext.HomeProductSelectedCommand, Source={x:Reference MyContentPage}} CommandParameter="{Binding .}"
…

В этом примере передается обязательный контекст элемента (по умолчанию это сам элемент) параметру команды