为什么当我尝试访问绑定对象的属性时 Xamarin 不呈现任何内容？

Question

此处展示了我的 Xamarin MVVM 应用程序页面之一。它的XAML代码如下：

<?xml version="1.0" encoding="utf-8" ?>
<ContentPage ...>
    <ContentPage.Content>
        <RefreshView Command="{Binding Load}" IsRefreshing="{Binding IsBusy, Mode=TwoWay}">
           <ScrollView>
              <Label Text="{Binding MyClass.MyProperty}"/>    
           </ScrollView>
        </RefreshView>
    </ContentPage.Content>
</ContentPage>

这是背后的代码：

namespace MyNamespace {
   public partial class MyPage {
      private readonly MyModel _viewModel;
      
      public NewsDetailPage() {
         InitializeComponent();
         BindingContext = _viewModel = new MyModel();
      }

      protected override void OnAppearing() {
         base.OnAppearing();
         _viewModel.OnAppearing();
      }
   }
}

这是视图模型：

namespace MyOtherNamespace {
   public class MyModel {
      private string _myProperty;

      public MyModel() {
         MyClass = new MyClass ();
         Load= new Command(async () => await GetFromAPI("one"));
      }

      public Command Load { get; set; }
      public MyClass MyClass { get; set; }
      
      public string MyProperty{
         get => _myProperty;
         set {
            _date= _myProperty;
            SetProperty(ref _myProperty, value);
         }
      }

      public void OnAppearing() {
         IsBusy = true;
      }


      public async Task GetFromAPI(string x) {
         // News = load from a Web API and populates the MyProperty property
      }
}

最后，MyTypeclass定义为：

public class MyClass {
   public string MyProperty { get; set; }
}

我不明白为什么 <Label Text="{Binding MyClass.MyProperty}"/> 什么也没显示，即使我在调试过程中检查过属性 gest 从视图的 GetFromAPI() 方法中正确填充型号。

Answer 1

在 MyClass 中实现 INotifyPropertyChanged 接口，它在我这边有效：

public class MyModel
{
    public MyModel()
    {
        MyClass = new MyClass();
        MyClass.MyProperty = "abc";

        Load = new Command(async () => await GetFromAPI("one"));            
    }

    public Command Load { get; set; }
    public MyClass MyClass { get; set; }

    public bool IsBusy { get; private set; }

    public void OnAppearing()
    {
        IsBusy = true;
    }

    public async Task GetFromAPI(string x)
    {
        // News = load from a Web API and populates the MyProperty property

        MyClass.MyProperty = "efg";
    }
}

public class MyClass : INotifyPropertyChanged
{
    public event PropertyChangedEventHandler PropertyChanged;

    private string myProperty { get; set; }

    public string MyProperty
    {
        set
        {
            if (myProperty != value)
            {
                myProperty = value;

                if (PropertyChanged != null)
                {
                    PropertyChanged(this, new PropertyChangedEventArgs("MyProperty"));
                }
            }
        }
        get
        {
            return myProperty;
        }
    }
}

为什么当我尝试访问绑定对象的属性时 Xamarin 不呈现任何内容？

Why Xamarin renders nothing when I try to access a property of the binded object?

c#

data-binding

xaml

binding

xamarin

为什么当我尝试访问绑定对象的 属性 时 Xamarin 不呈现任何内容？

Why Xamarin renders nothing when I try to access a property of the binded object?

c#

data-binding

xaml

binding

xamarin

为什么当我尝试访问绑定对象的属性时 Xamarin 不呈现任何内容？