如何在Xamarin跨平台表单MVVM中删除列表视图项?

Question

如何删除Xamarin跨平台表单中的ListView项

<ViewCell.ContextActions>
        <MenuItem Text="Delete" IsDestructive="True" Command="Binding DleteItemCommand}" />
</ViewCell.ContextActions>

但我希望用户代码符合MVVM模式

Answer 1

所以，视图模型只是用于表示层，你需要与你的单元格而不是视图模型进行交互。执行以下步骤:

1。为单元格创建一个ViewModels的Observable集合。2. 将这个集合添加到ListView的ItemSource中。3.然后为命令添加回调方法

                    <ListView x:Name="citiesListView" ItemTapped="OnSelection">
                    <ListView.ItemTemplate>
                            <DataTemplate>
                        <ViewCell>
                            <ViewCell.ContextActions>
                                <MenuItem Clicked="DeleteAction" Text="Delete" IsDestructive="true" CommandParameter="{Binding .}" />
                            </ViewCell.ContextActions>
                            <StackLayout Padding="15,0">
                                  <Label 
                                    Text="{Binding .}"
                                    FontSize="30"
                                    VerticalTextAlignment="Center"
                                    HorizontalTextAlignment="Center"/>
                            </StackLayout>
                        </ViewCell>
                    </DataTemplate>
                </ListView.ItemTemplate>

然后在代码中:

    public partial class YourPage : ContentPage
{
    public ObservableCollection<string> YourCollection { get; set; }
    public YourPage()
    {
        InitializeComponent();
        // initialize at this point
        YourCollection = new ObservaleCollection(<Some collection of view models>);
        citiesListView.ItemsSource = YourCollection;
    }

    private void DeleteAction(object sender, System.EventArgs e)
    {
        var menuItem = ((MenuItem)sender);
        var yourViewModel = (YourViewModelType) menuItem.CommandParameter;
       YourCollection.Remove(yourViewModel);
     }

Answer 2

您可以添加ObservableCollection<YourType>，并在命令中删除元素。

var collection = new ObservableCollection<YourType>();
yourList.ItemSource = collection;
// in Command
public void OnDelete (object sender, EventArgs e) 
{
    // getting reference on menu item
    var menuItem = ((MenuItem)sender).CommandParameter;    
    // cast to underlying viewModel
    var yourObject = (YourType)menuItem;
    collection.Remove(yourObject);
}

Answer 3

是，它与MVVM模式兼容。你在ListView中有一个Cell它是viewModel的一个单一表示。使用它的方法你有下一个关系:"模型-视图模型-视图"。ObservableCollection对你在ListView的单元格中显示的ViewModels有一个引用，现在你可以很容易地删除你想要的单元格。在代码