如何将嵌套的 BindableLayout.ItemsSource 中的项目索引绑定到 CommandParameter - Xamarin [英] How to bind index of item in nested BindableLayout.ItemsSource to CommandParameter - Xamarin

问题描述

我想弄清楚如何从 XAML 中的列表中获取索引.

I'm trying to figure out how you can get the index from a list inside XAML.

背景

一个产品有多个规格类别/组，其中包含规格详细信息.

A product has multiple specification categories/groups which contain the specification details.

• 产品&Ingrediënten 是规范组.
• Land van afkomst:荷兰是规格详情

• Product & Ingrediënten are the specification groups.
• Land van afkomst : Nederland are the specs details

在 XAML 代码中，我使用了嵌套列表.应用程序需要传递索引，以便用户可以正确删除和添加规范.

In the XAML code, I'm using a nested list. The application needs to pass the Index so the users can delete and add specifications correctly.

绑定源=0"处的索引/>&命令参数=0"需要传递而不是0".

The index at Binding Source="0" /> & CommandParameter="0" needs to be passed instead of "0".

<StackLayout BindableLayout.ItemsSource="{Binding Product.Specifications}">
    <BindableLayout.ItemTemplate>
        <DataTemplate>
            <StackLayout>
                <Entry Text="{Binding Title, Mode=TwoWay}" />
                <StackLayout BindableLayout.ItemsSource="{Binding SpecificationDetails}">
                    <BindableLayout.ItemTemplate>
                        <DataTemplate>
                            <Grid>
                                <Grid.ColumnDefinitions>
                                    <ColumnDefinition Width=".44*" />
                                    <ColumnDefinition Width=".44*" />
                                    <ColumnDefinition Width=".12*" />
                                </Grid.ColumnDefinitions>
                                <Entry Grid.Row="0"
                                       Grid.Column="0"
                                       Text="{Binding Title}"
                                       Style="{StaticResource spec-entry-style}" />
                                <Entry Grid.Row="0"
                                       Grid.Column="1"
                                       Text="{Binding Description}"
                                       Style="{StaticResource spec-entry-style}" />
                                <!-- Delete specification detail -->
                                <Button Grid.Column="2"
                                        Text="X"
                                        Style="{StaticResource cancel-button-style}"
                                        Command="{Binding Path=BindingContext.DeleteSpecificationEntryCommand, Source={x:Reference Page}}">
                                    <Button.CommandParameter>
                                        <MultiBinding Converter="{StaticResource SpecsConverter}">
                                            <Binding Source="0" />
                                            <Binding Path="." />
                                        </MultiBinding>
                                    </Button.CommandParameter>
                                </Button>
                            </Grid>
                        </DataTemplate>
                    </BindableLayout.ItemTemplate>
                </StackLayout>
                <!-- Add specification detail -->
                <Button Text="Voeg specificatie toe"
                        Command="{Binding AddSpecicifationEntriesCommand}"
                        CommandParameter="0"
                        HorizontalOptions="Start" />
            </StackLayout>
        </DataTemplate>
    </BindableLayout.ItemTemplate>
</StackLayout>

<!-- Add Specification group -->
<Button Text="Voeg nieuwe specificatie toe"
        Command="{Binding AddNewSpecificationGroupCommand}" />

规格组模型:

public class SpecificationDbViewModel : INotifyPropertyChanged
{
    private int _id;
    private string _title;
    private ObservableCollection<SpecificationDetailDbViewModel> _specificationDetails;

    public int Id
    {
        get => _id;
        set 
        { 
            _id = value;
            RaisePropertyChanged(nameof(Id));
        }
    }

    public string Title
    {
        get => _title;
        set
        {
            _title = value;
            RaisePropertyChanged(nameof(Title));
        }
    }

    public ObservableCollection<SpecificationDetailDbViewModel> SpecificationDetails
    {
        get => _specificationDetails;
        set
        {
            _specificationDetails = value;
            RaisePropertyChanged(nameof(Title));
        }
    }


    public event PropertyChangedEventHandler PropertyChanged;

    public void RaisePropertyChanged(string propertyName)
    {
        PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));
    }
}

规格详细型号:

public class SpecificationDetailDbViewModel : INotifyPropertyChanged
{
    private int _id;
    private string _title;
    private string _description;

    public int Id
    {
        get => _id;
        set
        {
            _id = value;
            RaisePropertyChanged(nameof(Id));
        }
    }

    public string Title
    {
        get => _title;
        set
        {
            _title = value;
            RaisePropertyChanged(nameof(Title));
        }
    }
    public string Description
    {
        get => _description;
        set
        {
            _description = value;
            RaisePropertyChanged(nameof(Description));
        }
    }

    public event PropertyChangedEventHandler PropertyChanged;

    public void RaisePropertyChanged(string propertyName)
    {
        PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));
    }
}

我正在使用 MultiBinder 转换器将多个值传递给命令.删除规范的 ViewModel 中的 1 个方法:

I'm using a MultiBinder converter to pass multiple values to the command. 1 method inside the ViewModel that removes the specifications:

private void ExecuteDeleteSpecificationEntryCommand(SpecificationDetailWithIndex specificationDetailWithIndex)
{
    Product.Specifications[specificationDetailWithIndex.Index].SpecificationDetails.Remove(specificationDetailWithIndex.SpecificationDetailDbViewModel);
}

推荐答案

1. 不要打扰您的索引，只需将 THE 对象作为命令的参数发回即可.

Command="{...}"  //same binding
CommandParameter="{Binding .}"  //new line

1. 并在您的 ViewModel 中使用正确的参数定义您的命令.

    public ICommand<SpecificationDetailDbViewModel> DeleteSpecificationEntryCommand => new Command<SpecificationDetailDbViewModel>(ExecuteDeleteSpecificationEntryCommand);

    private void ExecuteDeleteSpecificationDetailEntryCommand(SpecificationDetailDbViewModel item)
    {
        //remvoe item from collection
        Product.Specifications?.Remove(item);
    }

您还可以使用 组在列表视图中顺便说一句.

And you can also use groups in the list view btw.

这篇关于如何将嵌套的 BindableLayout.ItemsSource 中的项目索引绑定到 CommandParameter - Xamarin的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！