Listview中的按钮命令未触发

Question

我有一个显示 ObservableCollection 的 ListView。 Listview的每一项都有一个按钮和一个带有“AggiungiCommand”绑定的Command和一个CommandParameter。 当我单击按钮时，该命令不会触发。 这是代码：

<ContentPage xmlns: …
             x:Name="MieiAcquistiViewPage"
...
    <StackLayout CompressedLayout.IsHeadless="True">
        <StackLayout.BindingContext>
            <local:MieiAcquistiViewModel/>
        </StackLayout.BindingContext>

          <ListView x:Name="listView"
                      ItemsSource="{Binding AcquistiList}"
                      ItemTapped="listView_ItemTapped"
                      CachingStrategy="RecycleElement">

                <ListView.ItemTemplate>
                    <DataTemplate>
                        <ViewCell>
                            <Frame Style="{StaticResource frameListView}" >
                                <StackLayout Margin="-15">
                                    <Label Text="{Binding Articolo.Descrizione}" />
                                    <StackLayout Orientation="Horizontal" 
                                                 HorizontalOptions="Fill" VerticalOptions="CenterAndExpand" >

                                        <StackLayout Orientation="Horizontal"
                                                     HorizontalOptions="StartAndExpand" VerticalOptions="CenterAndExpand" >
                                            <Label Margin="10,0,0,0"
                                                       Text="{Binding Prezzo, StringFormat='{}{0:€ 0.00}'}"
                                                       HorizontalOptions="StartAndExpand" />
                                        </StackLayout>

                                        <StackLayout Orientation="Horizontal"
                                                     HorizontalOptions="End" VerticalOptions="Center">                                    

                                                <Label Text="{Binding QtaEdit}" 
                                                       TextColor="Black"
VerticalTextAlignment="Center"                                                       VerticalOptions="FillAndExpand"/>

                                            <Button x:Name="addButton" 
                                                    VerticalOptions="Center"
                                                    HorizontalOptions="Center"
                                                    Text="+"         
                                                    Command="{Binding AggiungiCommand, Source={x:Reference MieiAcquistiViewPage}}" 
    CommandParameter="{Binding .}"/>
                                        </StackLayout>
                                    </StackLayout>
                                </StackLayout>
                            </Frame>
                        </ViewCell>
                    </DataTemplate>
                </ListView.ItemTemplate>
            </ListView>
</StackLayout>
...
</ContentPage/>

在我看来 model class：

        public MieiAcquistiViewModel()
        {    
            AggiungiCommand = new Command<RigaStoricoModel>(AggiungiArticolo);            
        }

        public void AggiungiArticolo(RigaStoricoModel prodotto) 
        {
            // some stuff
        }

        public ICommand AggiungiCommand { private set; get; }

Answer 1

Command="{Binding MieiAcquistiViewModel.AggiungiCommand, Source={x:Reference MieiAcquistiViewPage}}更改为Command="{Binding BindingContext.AggiungiCommand, Source={x:Reference MieiAcquistiViewPage}} 。 请注意我如何用BindingContext.替换MieiAcquistiViewModel 。 .

假设您正在引用该页面，并且您想要访问支持该页面的视图 model 中的命令。

Answer 2

如果您已经附加了视图模型，则无需在绑定中为 AggiungiCommand 加上“MieiAcquistiViewModel”前缀。 你可以这样做：

Command="{Binding  Source={x:Reference MieiAcquistiViewPage}, Path=BindingContext.AggiungiCommand,Mode=TwoWay}" CommandParameter="{Binding .}" />