Xamarin 对象数据绑定

Question

我正在使用 Xamarin 创建一个应用程序，我正在从一个 api 获取数据并尝试在我的视图中显示它，在我的 ListView 中更具体

这是我的xaml 文件

<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"

         mc:Ignorable="d"
         x:Class="Reciper2.View.RecetaView">
<ContentPage.Content>
    <StackLayout>
        <Label Text="Prueba de compartir datos xamarin"
               VerticalOptions="Start"
               HorizontalOptions="Center">

        </Label>
        <Label Text="{Binding nombreReceta, StringFormat='Recetas de {0:F0}'}"
            VerticalOptions="Center" 
            HorizontalOptions="CenterAndExpand" />
        <Image Source="{Binding fotoReceta}"
               VerticalOptions="Center"
               HorizontalOptions="CenterAndExpand">
        </Image>
        <ListView     x:Name="listadoRecetas"
                      VerticalOptions="Center"
                      HorizontalOptions="StartAndExpand"
                      ItemsSource="{Binding RecetasList}">
            <ListView.ItemTemplate>
                <DataTemplate>
                    <TextCell Detail="{Binding nombre}"
                              Text="{Binding calorias}">

                    </TextCell>
                </DataTemplate>
            </ListView.ItemTemplate>
        </ListView>
    </StackLayout>
</ContentPage.Content>

我的xaml.cs 文件就是这个。

ObservableCollection<RecetaModel> recetasList = new ObservableCollection<RecetaModel>();
    public ObservableCollection<RecetaModel> RecetasList { get { return recetasList; } }


    public RecetaView()
    {
        InitializeComponent();
        this.BindingContext = this;
        listadoRecetas.ItemsSource = recetasList;
        getRecipes();


    }
   /* protected async override void OnAppearing()
     {
         getRecipes();
         base.OnAppearing();
     }*/
    public async void getRecipes()
    {

        var tipoReceta = this.BindingContext as RecetasModel;
        if(tipoReceta != null)
        {


             HttpWebRequest request = (HttpWebRequest)HttpWebRequest.Create(new Uri(url));
             request.ContentType = "application/json";
             request.Method = "GET";


             using (WebResponse response =  await request.GetResponseAsync())
             {
                using (Stream stream = response.GetResponseStream())
                {
                    JsonValue jsonDoc = await Task.Run(() => JsonObject.Load(stream));
                    var jsonString = jsonDoc.ToString();
                    dynamic objetoRecetas = JsonConvert.DeserializeObject(jsonString);
                    var listadoRecetas = objetoRecetas.hits;
                    foreach(dynamic receta in listadoRecetas)
                        {
                        dynamic rec = receta.recipe;
                        string nombre = rec.label;
                        string imagen = rec.image;
                        string calorias = rec.calories;
                        recetasList.Add(new RecetaModel { nombre = nombre, imagen= imagen, calorias = calorias});
                        }
                    // await DisplayAlert("Alert", jsonDoc, "OK");
                 }
             }

        }
    }

这是我的RecetaModel 课程。

 public class RecetaModel
{
    public string nombre { get; set; }
    public string imagen { get; set; }
    public string calorias { get; set; }

}

但在我看来没有任何显示。 知道我做错了什么吗？ 提前致谢。

Answer 1

由于某种原因，这在 OnAppearing 事件中调用我的方法时有效

public RecetaView()
    {
        InitializeComponent();
        this.BindingContext = this;
        listadoRecetas.ItemsSource = recetasList;

    }
    protected async override void OnAppearing()
     {
         getRecipes();
         base.OnAppearing();
     }