从 BindableLayout 检索 ItemsSource

Question

我有一个 FlexLayout 和一个 BindableLayout。

<FlexLayout BindableLayout.ItemsSource="{Binding CardItems}" x:Name="SourceLayout" Background="green"
                    Direction="Row" Wrap="Wrap">
                <BindableLayout.ItemTemplate>
                    <DataTemplate>
                        <ContentView>
                            <Frame CornerRadius="20" Padding="0" WidthRequest="150" Margin="10"
                            HeightRequest="150"
                            BackgroundColor="{Binding ., 
                            Converter={StaticResource AlternateColorConverter}, 
                            ConverterParameter={x:Reference SourceLayout}}">
                                <StackLayout>
                                    <StackLayout.GestureRecognizers>
                                        <TapGestureRecognizer Command="{Binding Path=BindingContext.CardItemNavCommand, Source={x:Reference SourceLayout}}"
                                                              CommandParameter="{Binding NavTarget}"/>
                                    </StackLayout.GestureRecognizers>
                                    <Label Text="{Binding Text}" TextColor="Black" FontSize="20" VerticalOptions="FillAndExpand"/>
                                    <Label Text="{Binding Text}" TextColor="Black" FontSize="20" VerticalOptions="FillAndExpand"/>
                                </StackLayout>
                            </Frame>
                        </ContentView>
                    </DataTemplate>
                </BindableLayout.ItemTemplate>
            </FlexLayout>

是否可以在转换器中获取当前项目的索引，以便相应地更改颜色？我知道这可以通过 ListView 实现，因为我可以访问项目源属性但我无法从 BindableLayout.

访问资源

Answer 1

Is it possible to get the index of the current item inside the converter so I can change the color accordingly

BindableLayout是静态的class，所以我们无法从布局中获取itemsSource。

对于此功能，尝试在模型 class 中创建一个 'Identifier' 属性并设置背景色的绑定。然后获取转换器中的值class从数据集合中获取当前项的索引。根据索引指定背景颜色

查看代码：

App.xaml.cs

public partial class App : Application
{
    public static TestPageViewModel viewModel;
    public App()
    {
        InitializeComponent();

        viewModel = new TestPageViewModel();

        MainPage = new NavigationPage(new TestPage());
    }
}

Page.xaml

<StackLayout BindableLayout.ItemsSource="{Binding DataCollection}" ...>
    <BindableLayout.ItemTemplate>
        <DataTemplate>
            <Grid Padding="0,2,3,0" BackgroundColor="{Binding Identifier, Converter={StaticResource _converter}}">
                ...
            </Grid>
        </DataTemplate>
    </BindableLayout.ItemTemplate>
</StackLayout>

Page.xaml.cs

public partial class TestPage : ContentPage
{
    public TestPage()
    {
        InitializeComponent();

        BindingContext = App.viewModel;
    }
}

型号class

public class TestPageModel
{
    public string Content { get; set; }

    public string Identifier { get; set; }
}

值转换器class

public class TestPageValueConverter : IValueConverter
{
    public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
    {
        var index = GetValue(value);
        switch (index)
        {
            case 1:
                return Color.LightBlue;
                break;
            case 2:
                return Color.LightPink;
                break;
            case 3:
                return Color.LightYellow;
                break;

            default:
                break;
        }
        return Color.White;
    }

    public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
    {
        return -1;
    }

    double GetValue(object value)
    {
        var viewModel = App.viewModel;
        foreach (var item in viewModel.DataCollection)
        {
            if (item.Identifier == (string)value)
            {
                return viewModel.DataCollection.IndexOf(item) + 1;
            }
        }
        return -1;
    }
}

从 BindableLayout 检索 ItemsSource

Retrieving ItemsSource from a BindableLayout

data-binding

xaml

xamarin

xamarin.forms