Xamarin.Forms + ReactiveUI + Xamvvm僅在iOS上查看不更新

Question

我們正在使用Xamarin.Forms和ReactiveUI構建一個跨平臺的應用程序。 該應用程序結構是基於下面的例子：

https://github.com/GiusepeCasagrande/reactive-dev-days-lab

Android版正常工作，但是，在iOS模擬器，當你運行命令「SyncSpeakers」，命令成功執行，視圖閃爍但列表不填充。

任何人都可以理解爲什麼會發生這種情況嗎？ 我是否應該放棄使用xammvvm進行路由並切換到別的東西？

用於揚聲器的視圖模型的代碼如下：

using System; 
using System.Collections.Generic; 
using System.Diagnostics; 
using System.Linq; 
using System.Reactive; 
using System.Reactive.Linq; 
using DevDaysSpeakers.Model; 
using DevDaysSpeakers.Services; 
using ReactiveUI; 
using Xamarin.Forms; 
using Xamvvm; 

namespace DevDaysSpeakers.ViewModel 
{ 
    public class SpeakersViewModel: BasePageModelRxUI 
    { 
     public ReactiveList<Speaker> Speakers { get; } = new ReactiveList<Speaker>(); 

     Speaker speaker; 
     public Speaker Speaker 
     { 
      get { return speaker; } 
      set { this.RaiseAndSetIfChanged(ref speaker, value); } 
     } 

     public ReactiveCommand<Unit, IEnumerable<Speaker>> GetSpeakers { get; } 

     public ReactiveCommand GoToDetails { get; } 

     readonly ObservableAsPropertyHelper<bool> busy; 
     public bool IsBusy => busy.Value; 

     public SpeakersViewModel() 
      : this(null) 
     { 

     } 

     public SpeakersViewModel(AzureService azureService = null) 
     { 
      var service = azureService ?? DependencyService.Get<AzureService>(); 

      GetSpeakers = ReactiveCommand.CreateFromTask(_ => service.GetSpeakers()); 

      GetSpeakers 
       .ObserveOn(RxApp.MainThreadScheduler) 
       .SubscribeOn(RxApp.MainThreadScheduler) 
       .Subscribe(speakers => 
       { 
        Speakers.Clear(); 
        Speakers.AddRange(speakers); 
       }); 

      GetSpeakers.IsExecuting 
       .ToProperty(this, vm => vm.IsBusy, out busy); 

      GetSpeakers.ThrownExceptions 
       .Subscribe(error => Application.Current.MainPage.DisplayAlert("Error!", error.Message, "OK")); 

      // go to details page when Speaker is set 
      this.WhenAnyValue(vm => vm.Speaker) 
       .Where(speaker => speaker != null) 
       .Subscribe(speaker => this.PushPageFromCacheAsync<DetailsViewModel>(vm => vm.Speaker = speaker)); 

      this.ThrownExceptions 
       .Subscribe(ex => 
      { 
       Debug.WriteLine(ex.Message); 
      }); 
     } 
    } 
} 

的XAML爲視圖：

<?xml version="1.0" encoding="utf-8"?> 
<reactive:ReactiveContentPage xmlns="http://xamarin.com/schemas/2014/forms" 
    xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml" 
    xmlns:reactive="clr-namespace:ReactiveUI.XamForms;assembly=ReactiveUI.XamForms" 
    xmlns:xamvvm="clr-namespace:Xamvvm;assembly=Xamvvm.Forms.RxUI" 
    xmlns:local="clr-namespace:DevDaysSpeakers.ViewModel;assembly=DevDaysSpeakers" 
    x:Class="DevDaysSpeakers.View.SpeakersPage" 
    x:TypeArguments="local:SpeakersViewModel" 
    Title="Speakers" 
    x:Name="ThePage"> 
    <reactive:ReactiveContentPage.Padding> 
     <OnPlatform x:TypeArguments="Thickness" iOS="0, 20, 0, 0" /> 
    </reactive:ReactiveContentPage.Padding> 
    <reactive:ReactiveContentPage.Content> 
     <StackLayout Spacing="0"> 
      <Button x:Name="SyncSpeakers" Text="Sync Speakers" /> 
      <ActivityIndicator x:Name="IsBusy" /> 
      <ListView x:Name="ListViewSpeakers"> 
       <ListView.ItemTemplate> 
        <DataTemplate> 
         <ImageCell Text="{Binding Name}" Detail="{Binding Title}" ImageSource="{Binding Avatar}" /> 
        </DataTemplate> 
       </ListView.ItemTemplate> 
      </ListView> 
     </StackLayout> 
    </reactive:ReactiveContentPage.Content> 
</reactive:ReactiveContentPage> 

代碼的視圖的背後

using System.Reactive.Disposables; 
using DevDaysSpeakers.ViewModel; 
using ReactiveUI; 
using Xamvvm; 

namespace DevDaysSpeakers.View 
{ 
    public partial class SpeakersPage 
     : IBasePageRxUI<SpeakersViewModel> 
    { 
     public SpeakersPage() 
     { 
      InitializeComponent(); 

      this.WhenActivated(disposables => 
      { 
       this.OneWayBind(ViewModel, x => x.Speakers, x => x.ListViewSpeakers.ItemsSource).DisposeWith(disposables); 
       this.OneWayBind(ViewModel, x => x.GetSpeakers, x => x.SyncSpeakers.Command).DisposeWith(disposables); 
       this.OneWayBind(ViewModel, x => x.IsBusy, x => x.IsBusy.IsVisible).DisposeWith(disposables); 
       this.OneWayBind(ViewModel, x => x.IsBusy, x => x.IsBusy.IsEnabled).DisposeWith(disposables); 
       this.Bind(ViewModel, x => x.Speaker, x => x.ListViewSpeakers.SelectedItem).DisposeWith(disposables); 
      }); 
     } 
    } 
} 

Project.json爲iOS

{ 
    "supports": {}, 
    "dependencies": { 
    "Microsoft.Azure.Mobile.Client.SQLiteStore": "3.1.0", 
    "Microsoft.Bcl.Build": "1.0.21", 
    "reactiveui-events-xamforms": "7.1.0", 
    "reactiveui-xamforms": "7.1.0", 
    "SQLitePCLRaw.bundle_e_sqlite3": "1.1.2", 
    "Xam.Plugins.TextToSpeech": "2.0.0", 
    "Xamarin.Forms": "2.3.3.180", 
    "Xamvvm.Forms.RxUI": "1.0.2" 
    }, 
    "frameworks": { 
    ".NETPortable,Version=v4.5,Profile=Profile7": {} 
    } 
} 

Answer 1

這是一個Xamarin.Forms錯誤。你可以看到的討論在這裏https://github.com/reactiveui/ReactiveUI/issues/806

這裏是錯誤本身：https://bugzilla.xamarin.com/show_bug.cgi?id=31415

在第一個鏈接，你可以找到一些解決方法，一個非常簡單的只是改變ReactiveList一個的ObservableCollection。