使用 Prism 库将 ListView 项传递给命令

Question

我正在尝试根据列表视图项目数据执行方法。除此之外，触发命令的按钮应该只在列表视图项的“CanExecute”方法返回 true 时启用。

“MyCommand”和“CanExecute”这两种方法都包含在我的 ViewModel 中。不幸的是，我不确定如何将项目信息正确地传递给这两种方法以符合 PRISM 6 框架。

所以我的第一种方法是这样做：

模型

public class MyModel
{
    public string Name { get; set; }
    public string Version { get; set; }
    public int Identifier { get; set; }
}

视图模型

public class MyViewModel : BindableBase
{

    private ObservableCollection<MyModel> _models = new ObservableCollection<MyModel>();
    public ObservableCollection<MyModel> Models
    {
        get { return _models; }
        set { SetProperty(ref _models, value); }
    }

    public DelegateCommand VerifyCommand { get; set; }


    public MyViewModel()
    {
        //Add test data
        for (int i = 0; i < 5; i++)
        {
            MyModel model = new MyModel();
            model.Name = "Random Text";
            model.Version = "Random Text";
            model.Identifier = i;

            Models.Add(model);
        }

        //Doesn't work, because I don't reference to "Models"
        //How to do that?
        VerifyCommand = new DelegateCommand(DoCommand, CanExecute).ObservesProperty<string>(() => Name).ObservesProperty<string>(() => Version);
    }

    private bool CanExecute()
    {
        //Obviously this doesn't work, because "Version" and "Name" 
        //don't belong to the selected "Models" item of the listview

        //What is the "bridge", to know which item of Models was clicked (button)
        return !String.IsNullOrWhiteSpace(Version) && !String.IsNullOrWhiteSpace(Name);
    }

    private void DoCommand()
    {
        //Do something special
    }
}

看法

<ListView ItemsSource="{Binding Models}">
    <ListView.ItemTemplate>
        <DataTemplate>
            <Grid Height="Auto" Margin="0,0,0,10">
                <Grid.RowDefinitions>
                    <RowDefinition/>
                    <RowDefinition/>
                    <RowDefinition/>
                </Grid.RowDefinitions>
                <TextBox Grid.Row="0" Tag="VERSION" Text="{Binding Version, UpdateSourceTrigger=PropertyChanged}" />
                <TextBox Grid.Row="1" Tag="NAME" Text="{Binding Name, UpdateSourceTrigger=PropertyChanged}" />
                <Button Command="{Binding ElementName=root, Path=DataContext.VerifyCommand}" Content="Verify" Grid.Row="2">
            </Grid>
        </DataTemplate>
    </ListView.ItemTemplate>
</ListView>

View 和 ViewModel 之间的链接是通过使用完成的：

prism:ViewModelLocator.AutoWireViewModel="True"

在我看来（这有效）。

所以总结一下：它是如何工作的，PRISM 符合 1. 仅当 CanExecute 为 true 时才启用项目按钮 2. 执行“DoCommand”方法并将项目信息传递给该方法（按钮的根元素 -> 在这种情况下ListViewItem (MyModel)。

任何帮助将不胜感激。

Answer 1

简短回答：将命令放在项目的视图模型中。

长答案：

这是我在上面评论中的意思的一个例子。我已经省略了集合的可观察性，如果你真的需要一个可观察的模型集合和一个可观察的视图模型集合，请为大量无聊的双向同步代码做好准备......

模型：

internal class ItemModel
{
    public string Name { get; set; }
    public string Version { get; set; }
    public int Identifier { get; set; }
}

ViewModels（一个用于项目集合，即您的MyViewModel，一个用于项目）：

internal class MyCollectionViewModel : BindableBase
{
    private readonly List<ItemModel> _models = new List<ItemModel>();

    public MyCollectionViewModel()
    {
        //Add test data
        for (var i = 0; i < 5; i++)
            _models.Add( new ItemModel
            {
                // to prove that CanExecute is actually evaluated...
                Name = i == 3 ? "Random Text" : string.Empty,
                Version = "Random Text",
                Identifier = i
            } );
    }

    public IReadOnlyCollection<ItemViewModel> TheCollection => _models.Select( x => new ItemViewModel( x ) ).ToList();
}

internal class ItemViewModel : BindableBase
{
    public ItemViewModel( ItemModel item )
    {
        _item = item;
        VerifyCommand = new DelegateCommand( () =>
                                             {
                                                 /* Do something */
                                             }, () => !string.IsNullOrWhiteSpace( Version ) && !string.IsNullOrWhiteSpace( Name ) );
    }

    public string Name => _item.Name;
    public string Version => _item.Version;
    public int Identifier => _item.Identifier;

    public DelegateCommand VerifyCommand
    {
        get;
    }

    private readonly ItemModel _item;
}

看法：

<ListView ItemsSource="{Binding TheCollection}">
    <ListView.ItemTemplate>
        <DataTemplate>
            <Grid Height="Auto" Margin="0,0,0,10">
                <Grid.ColumnDefinitions>
                    <ColumnDefinition/>
                    <ColumnDefinition/>
                    <ColumnDefinition/>
                </Grid.ColumnDefinitions>
                <TextBox Grid.Column="0" Text="{Binding Version, Mode=OneWay}" />
                <TextBox Grid.Column="1" Text="{Binding Name, Mode=OneWay}" />
                <Button Grid.Column="2" Command="{Binding VerifyCommand}" Content="Verify"/>
            </Grid>
        </DataTemplate>
    </ListView.ItemTemplate>
</ListView>