从Button命令获取ListView xamarin.forms MVVM

Question

在我的xamarin.forms应用程序中我的ListView上有一个问题,我使用MVVM模式.我希望你能帮助我.这是我的xaml:

 <ListView x:Name="MissingVolumeListView"  
                          ItemsSource="{Binding Volumes}"
                          SelectedItem ="{Binding Id}"
                             >
                            <ListView.ItemTemplate>
                                <DataTemplate>
                                    <ViewCell>
                                        <Grid x:Name="Item">
                                            <Grid.ColumnDefinitions>
                                                <ColumnDefinition Width="*"/>
                                                <ColumnDefinition Width="40"/>
                                            </Grid.ColumnDefinitions>
                                            <Label  Text="{Binding Name}" Style="{StaticResource UsualLabelTemplate}"/>
                                            <Button Grid.Column="1" x:Name="DeleteButton" Text ="-" BindingContext="{Binding Source={x:Reference MissingVolumeListView}, Path=BindingContext}"   Command="{Binding DeleteVolumeCommand}" CommandParameter="{Binding Source={x:Reference Item}, Path=BindingContext}"/>
                                        </Grid>
                                    </ViewCell>
                                </DataTemplate>
                            </ListView.ItemTemplate>
                        </ListView>

然后我在ViewModel中获取DeleteVolumeCommand:

 private ICommand _deleteVolumeCommand;
    public ICommand DeleteVolumeCommand
    {
        get
        {
            {
                if (_deleteVolumeCommand == null)
                {
                    _deleteVolumeCommand = new Command((e) =>
                    {
                        var item = (e as Volume);
                        int index = MissingVolumeListView.Items.IndexOf(item);                       
                    });
                }

                return _deleteVolumeCommand;
            }

        }
    }

正如您所看到的,当我单击ListView中的Button时,我想要的是获取所选项目.然后,我想让我的ListView获取所选项目的索引,以便从我的ListView中删除它

谢谢您的帮助

Answer 1

首先更改删除按钮XAML.

<Button Grid.Column="1" 
        Text ="-" 
        Command="{Binding Path=BindingContext.DeleteVolumeCommand, Source={x:Reference MissingVolumeListView}}" 
        CommandParameter="{Binding .}" /> 

该命令需要通过listview名称将其绑定上下文更改为视图模型.

但是,命令参数只能传递当前绑定,即列表视图项.

在视图模型中,您无法通过名称引用任何控件.而是使用列表视图将其ItemsSource绑定到的列表 - Volumes.

您可以直接删除该项目.

_deleteVolumeCommand = new Command((e) =>
{
    var item = (e as Volume);
    Volumes.Remove(item);                       
});

如果Volumes不是ObservableCollection,请记住也调用notify属性.