如何发送一个参数到ContentView?

Question

我正在尝试创建一个包含XamarinCommunityToolkit的TabView的ContentPage。

让我们说标签定义了类别的ObservableCollection，每个TabViewItem应该加载一个ContentView并传递一个GroupId作为参数/属性，然后我使用该GroupId来过滤产品列表。

传递参数给ContentView的最好方法是什么?

更新:

我已经尝试使用bindableproperty，但是，在调试器中，我可以看到收到的newValue，但没有显示在标签:

MainPage.xaml

<?xml version="1.0" encoding="utf-8" ?>
<ContentPage xmlns="http://xamarin.com/schemas/2014/forms"
xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
xmlns:d="http://xamarin.com/schemas/2014/forms/design"
xmlns:mc="http://schemas.openxmlformats.org/markup- 
compatibility/2006"
xmlns:xct="http://xamarin.com/schemas/2020/toolkit"
mc:Ignorable="d"
x:Class="mynamespace.Views.MainPage"
Title="{Binding Title}"
xmlns:local="clr-namespace:mynamespace.Views"
xmlns:vm="clr-namespace:mynamespace.ViewModels"
xmlns:model="clr-namespace:mynamespace.Models"  
x:Name="MainPage">
<ContentPage.Content>
<xct:TabView Grid.Row="0"
TabStripPlacement="Top"
TabStripBackgroundColor="White"
TabStripHeight="48"
TabIndicatorColor="Orange"
TabIndicatorHeight="2"
TabItemsSource="{Binding Categories}">
<xct:TabView.TabViewItemDataTemplate>
<DataTemplate>
<Grid>
<Label Text="{Binding Name}"
FontAttributes="Bold"
VerticalOptions="Center"
Padding="6, 0"/>
</Grid>
</DataTemplate>
</xct:TabView.TabViewItemDataTemplate>
<xct:TabView.TabContentDataTemplate>
<DataTemplate>
<local:GroupView GroupId="{Binding Id}" />
</DataTemplate>
</xct:TabView.TabContentDataTemplate>
</xct:TabView>
</ContentPage.Content>

GroupView.xaml.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using Xamarin.Forms;
using Xamarin.Forms.Xaml;
namespace mynamespace.Views
{
public partial class GroupView : ContentView
{        
public  string GroupId
{
get { return (string)GetValue(GroupIdProperty); }
set { SetValue(GroupIdProperty, value); }
}
public static readonly BindableProperty GroupIdProperty = BindableProperty.Create(
nameof(GroupId),
typeof(string),
typeof(GroupView),
"Default_V",
defaultBindingMode: BindingMode.OneWay,
propertyChanged: GroupIdChanged
);
private static void GroupIdChanged(BindableObject bindable, object oldValue, object newValue)
{
var control = (ProductListPage)bindable;
control.GroupId = newValue?.ToString();

}
public GroupView()
{
InitializeComponent();
BindingContext = this;
}
}
}

GroupView.xaml

<?xml version="1.0" encoding="UTF-8"?>
<ContentView xmlns="http://xamarin.com/schemas/2014/forms" 
xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
x:Class="mynamespace.Views.GroupView">
<ContentView.Content>
<StackLayout>
<Label Text="{Binding GroupId}" /> <!-- Shows nothing -->
</StackLayout>
</ContentView.Content>
</ContentView>

目录类:

public class Category
{
private string id;
private string name;
private string description;
public string Id { get => id; set => id = value; }
public string Name { get => name; set => name = value; }
public string Description { get => description; set => description = value; }
}

ProductListViewModel.cs

public class ProductListViewModel : BaseViewModel
{
public string GroupId { get; set; }
public ProductListViewModel()
{
}
public ProductListViewModel(string groupId)
{
GroupId = groupId;
}
}

更新:

[0:] Binding: 'GroupId' property not found on 'mynamespace.Models.Category', target property: 'Xamarin.Forms.Label.Text'

Answer 1

不要在自定义控件内部分配绑定。你可以这样做:

public partial class GroupView : ContentView
{
GroupViewModel _viewModel;

public string GroupId
{
get { return (string)GetValue(GroupIdProperty); }
set { SetValue(GroupIdProperty, value); }
}
public static readonly BindableProperty GroupIdProperty = BindableProperty.Create(
nameof(GroupId),
typeof(string),
typeof(GroupView),
"Default_V",
defaultBindingMode: BindingMode.OneWay,
propertyChanged: GroupIdChanged
);
private static void GroupIdChanged(BindableObject bindable, object oldValue, object newValue)
{
var control = (GroupView)bindable;
control.GroupId = (string)newValue;
control.label.Text = control.GroupId;

}
public GroupView()
{
InitializeComponent();
}
}

<?xml version="1.0" encoding="UTF-8"?>
<ContentView xmlns="http://xamarin.com/schemas/2014/forms" 
xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
x:Class="mynamespace.Views.GroupView">
<ContentView.Content>
<StackLayout>
<Label x:Name="label"  /> 
</StackLayout>
</ContentView.Content>
</ContentView>