xamarin - Prism :在 ViewModel 中设置值后 View 没有更新？

Question

我无法从 ViewModel 将值绑定(bind)到 View，我可以看到值正在设置(ServiceList)

这是 Xaml

XAML:

<Label
                    Grid.Row="0"
                    FontFamily="{StaticResource BoldFont}"
                    FontSize="{StaticResource NormalFontSize}"
                    HorizontalOptions="StartAndExpand"
                    Text="{Binding Heading, Mode=TwoWay}"
                    TextColor="Black"
                    VerticalOptions="CenterAndExpand" />

页面 View 模型:

    private string _Heading;
        public string Heading
        {
            get { return _Heading; }
            set { _Heading = value; SetProperty(ref _Heading, value); }
        }

async void LoadData(Service service)
        {
            Dictionary<string, string> data = new Dictionary<string, string>();
            if (App.Current.Properties.ContainsKey("user_id"))
                data.Add("user_id", App.Current.Properties["user_id"].ToString());
            data.Add("subcategory", service.id.ToString());
            data.Add("city", "ABC");
            UserResponse = await HomeService.GetServices(data);
            if (UserResponse.status == 200)
            {
                Heading = "529 Interior Decorators in Las Vegas";
            }
        }

Answer 1

这是因为 SetProperty只加注 PropertyChanged如果值实际发生变化。通过预先设置它，您可以防止这种情况发生，并且 View 无法知道它应该更新。

你想写:

public string Heading
{
    get { return _Heading; }
    set { SetProperty(ref _Heading, value); }
}

注意缺少的 _Heading = value;