Mvvmcross: kann keine Präferenzaktivität erstellen

Question

Ich arbeite an einem Xamarin-Projekt, das mit MvvmCross läuft. Ich versuche eine Einstellungsansicht in Android hinzuzufügen, aber ich kann es nicht zum Laufen bringen.

Wenn ich versuche, auf die MvxPreferenceFragment zu navigieren, erhalte ich folgende Fehler:

[0:] mvx:Diagnostic: 12.11 Activity host with ViewModelType PreferenceTest.Droid.Activities.MainPreferenceActivity is not CurrentTopActivity. Showing Activity before showing Fragment for PreferenceTest.Core.ViewModels.Fragments.PreferenceViewModel 
An unhandled exception occured. 

09-26 13:54:45.753 I/MonoDroid(12779): UNHANDLED EXCEPTION: 
09-26 13:54:45.810 I/MonoDroid(12779): System.Collections.Generic.KeyNotFoundException: Could not find view for PreferenceTest.Droid.Activities.MainPreferenceActivity 
09-26 13:54:45.810 I/MonoDroid(12779): at MvvmCross.Core.Views.MvxViewsContainer.GetViewType (System.Type viewModelType) [0x0006a] in C:\projects\mvvmcross\MvvmCross\Core\Core\Views\MvxViewsContainer.cs:72 
09-26 13:54:45.810 I/MonoDroid(12779): at MvvmCross.Droid.Support.V7.AppCompat.MvxAppCompatViewPresenter.ShowHostActivity (MvvmCross.Droid.Views.Attributes.MvxFragmentPresentationAttribute attribute) [0x00000] in C:\projects\mvvmcross\MvvmCross-AndroidSupport\MvvmCross.Droid.Support.V7.AppCompat\MvxAppCompatViewPresenter.cs:166 
09-26 13:54:45.810 I/MonoDroid(12779): at MvvmCross.Droid.Support.V7.AppCompat.MvxAppCompatViewPresenter.ShowFragment (System.Type view, MvvmCross.Droid.Views.Attributes.MvxFragmentPresentationAttribute attribute, MvvmCross.Core.ViewModels.MvxViewModelRequest request) [0x0007d] in C:\projects\mvvmcross\MvvmCross-AndroidSupport\MvvmCross.Droid.Support.V7.AppCompat\MvxAppCompatViewPresenter.cs:196 
09-26 13:54:45.810 I/MonoDroid(12779): at MvvmCross.Droid.Views.MvxAndroidViewPresenter.<RegisterAttributeTypes>b__39_2 (System.Type view, MvvmCross.Core.Views.MvxBasePresentationAttribute attribute, MvvmCross.Core.ViewModels.MvxViewModelRequest request) [0x00000] in C:\projects\mvvmcross\MvvmCross\Droid\Droid\Views\MvxAndroidViewPresenter.cs:188 
09-26 13:54:45.810 I/MonoDroid(12779): at MvvmCross.Droid.Views.MvxAndroidViewPresenter.Show (MvvmCross.Core.ViewModels.MvxViewModelRequest request) [0x00055] in C:\projects\mvvmcross\MvvmCross\Droid\Droid\Views\MvxAndroidViewPresenter.cs:295 
09-26 13:54:45.810 I/MonoDroid(12779): at MvvmCross.Droid.Views.MvxAndroidViewDispatcher+<>c__DisplayClass2_0.<ShowViewModel>b__0() [0x00000] in C:\projects\mvvmcross\MvvmCross\Droid\Droid\Views\MvxAndroidViewDispatcher.cs:26 
09-26 13:54:45.810 I/MonoDroid(12779): at MvvmCross.Droid.Views.MvxAndroidMainThreadDispatcher.RequestMainThreadAction (System.Action action, System.Boolean maskExceptions) [0x00020] in C:\projects\mvvmcross\MvvmCross\Droid\Droid\Views\MvxAndroidMainThreadDispatcher.cs:20 
09-26 13:54:45.811 I/MonoDroid(12779): at MvvmCross.Droid.Views.MvxAndroidViewDispatcher.ShowViewModel (MvvmCross.Core.ViewModels.MvxViewModelRequest request) [0x00014] in C:\projects\mvvmcross\MvvmCross\Droid\Droid\Views\MvxAndroidViewDispatcher.cs:26 
09-26 13:54:45.811 I/MonoDroid(12779): at MvvmCross.Core.Navigation.MvxNavigationService+<Navigate>d__32.MoveNext() [0x0003a] in C:\projects\mvvmcross\MvvmCross\Core\Core\Navigation\MvxNavigationService.cs:179 
09-26 13:54:45.811 I/MonoDroid(12779): --- End of stack trace from previous location where exception was thrown --- 
09-26 13:54:45.811 I/MonoDroid(12779): at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw() [0x0000c] in <896ad1d315ca4ba7b117efb8dacaedcf>:0 
09-26 13:54:45.811 I/MonoDroid(12779): at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess (System.Threading.Tasks.Task task) [0x0003e] in <896ad1d315ca4ba7b117efb8dacaedcf>:0 
09-26 13:54:45.811 I/MonoDroid(12779): at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification (System.Threading.Tasks.Task task) [0x00028] in <896ad1d315ca4ba7b117efb8dacaedcf>:0 
09-26 13:54:45.811 I/MonoDroid(12779): at System.Runtime.CompilerServices.TaskAwaiter.ValidateEnd (System.Threading.Tasks.Task task) [0x00008] in <896ad1d315ca4ba7b117efb8dacaedcf>:0 
09-26 13:54:45.811 I/MonoDroid(12779): at System.Runtime.CompilerServices.ConfiguredTaskAwaitable+ConfiguredTaskAwaiter.GetResult() [0x00000] in <896ad1d315ca4ba7b117efb8dacaedcf>:0 
09-26 13:54:45.811 I/MonoDroid(12779): at MvvmCross.Core.Navigation.MvxNavigationService+<Navigate>d__40.MoveNext() [0x00078] in C:\projects\mvvmcross\MvvmCross\Core\Core\Navigation\MvxNavigationService.cs:293 
09-26 13:54:45.811 I/MonoDroid(12779): --- End of stack trace from previous location where exception was thrown --- 
09-26 13:54:45.811 I/MonoDroid(12779): at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw() [0x0000c] in <896ad1d315ca4ba7b117efb8dacaedcf>:0 
09-26 13:54:45.811 I/MonoDroid(12779): at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess (System.Threading.Tasks.Task task) [0x0003e] in <896ad1d315ca4ba7b117efb8dacaedcf>:0 
09-26 13:54:45.811 I/MonoDroid(12779): at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification (System.Threading.Tasks.Task task) [0x00028] in <896ad1d315ca4ba7b117efb8dacaedcf>:0 
09-26 13:54:45.811 I/MonoDroid(12779): at System.Runtime.CompilerServices.TaskAwaiter.ValidateEnd (System.Threading.Tasks.Task task) [0x00008] in <896ad1d315ca4ba7b117efb8dacaedcf>:0 
09-26 13:54:45.811 I/MonoDroid(12779): at System.Runtime.CompilerServices.TaskAwaiter.GetResult() [0x00000] in <896ad1d315ca4ba7b117efb8dacaedcf>:0 
09-26 13:54:45.811 I/MonoDroid(12779): at PreferenceTest.Core.ViewModels.FirstViewModel+<ExecutePreferences>d__8.MoveNext() [0x00026] in C:\git\PreferenceTest\PreferenceTest\PreferenceTest\PreferenceTest.Core\ViewModels\FirstViewModel.cs:28 
09-26 13:54:45.811 I/MonoDroid(12779): --- End of stack trace from previous location where exception was thrown --- 
09-26 13:54:45.811 I/MonoDroid(12779): at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw() [0x0000c] in <896ad1d315ca4ba7b117efb8dacaedcf>:0 
09-26 13:54:45.811 I/MonoDroid(12779): at System.Runtime.CompilerServices.AsyncMethodBuilderCore+<>c.<ThrowAsync>b__6_0 (System.Object state) [0x00000] in <896ad1d315ca4ba7b117efb8dacaedcf>:0 
09-26 13:54:45.811 I/MonoDroid(12779): at Android.App.SyncContext+<>c__DisplayClass2_0.<Post>b__0() [0x00000] in <2e14bb2dd93a405e81838369ed72695b>:0 
09-26 13:54:45.811 I/MonoDroid(12779): at Java.Lang.Thread+RunnableImplementor.Run() [0x00008] in <2e14bb2dd93a405e81838369ed72695b>:0 
09-26 13:54:45.811 I/MonoDroid(12779): at Java.Lang.IRunnableInvoker.n_Run (System.IntPtr jnienv, System.IntPtr native__this) [0x00008] in <2e14bb2dd93a405e81838369ed72695b>:0 
09-26 13:54:45.811 I/MonoDroid(12779): at (wrapper dynamic-method) System.Object:a278159c-f25c-4da4-ac29-d4bae0d2de73 (intptr,intptr) 

Dies ist der Code, den ich versuche (für den vollständigen Code unten entnehmen Sie bitte den Github Link) zu laufen : Zuerst habe ich einen Blick in den xML-Ordner (benannt preference.xml)

<?xml version="1.0" encoding="utf-8"?> 
<PreferenceScreen xmlns:android="http://schemas.android.com/apk/res/android"> 
    <EditTextPreference android:title="Your Name" 
         android:key="username" 
         android:summary="Please provide your username"></EditTextPreference> 
    <CheckBoxPreference android:title="Application Updates" 
         android:defaultValue="false" 
         android:summary="This option if selected will allow the application to check for latest versions." 
         android:key="applicationUpdates" /> 
    <ListPreference  android:title="Download Details" 
         android:summary="Select the kind of data that you would like to download" 
         android:key="downloadType" 
         android:defaultValue="1" 
         android:entries="@array/listArray" 
         android:entryValues="@array/listValues" /> 
    <CheckBoxPreference 
    android:key="prefer wifi" 
    android:title="Prefer WiFi" /> 
</PreferenceScreen> 

das Fragment Code auch:

[MvxFragmentPresentation(typeof(MainPreferenceActivity), Resource.Id.content_frame, true)] 
[Register(nameof(PreferenceFragment))] 
public class PreferenceFragment : MvxPreferenceFragment<PreferenceViewModel> 
{ 
    public override View OnCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) 
    { 
     base.OnCreateView(inflater, container, savedInstanceState); 
     var view = this.BindingInflate(Resource.Xml.preferences, container, false); 
     return view; 
    } 
} 

Der Anruf wird mit dem Navigationsdienst gemacht:

private async void ExecutePreferences() 
{ 
    await _navigationService.Navigate<PreferenceViewModel>(); 
} 

Ich kann nicht finden, was mit diesem Code falsch ist :).

Hier ist auch a github link zum Beispiel.

Answer 1

Das erste Problem ist mit der Verwendung der MvxFragmentPresentation der erste Parameter ist der Typ der ViewModel wird für die Host-Aktivität und nicht der Typ der Aktivität selbst verwendet. Was in Ihrem Fall wäre MainPreferenceViewModel.

Die nächste Frage ist, dass Sie den MvxAppCompatViewPresenter Presenter verwenden und Sie daher MvxPreferenceFragmentCompat verwenden müssen. MvxPreferenceFragmentCompat finden Sie im NuGet-Paket MvvmCross.Droid.Support.V7.Preference.

[MvxFragmentPresentation(typeof(MainPreferenceViewModel), Resource.Id.content_frame)] 
[Register(nameof(PreferenceFragment))] 
public class PreferenceFragment : MvxPreferenceFragmentCompat<PreferenceViewModel> 
{ 
    public override void OnCreatePreferences(Bundle savedInstanceState, string rootKey) 
    { 
     SetPreferencesFromResource(Resource.Xml.preferences, rootKey); 
    } 
} 

Schließlich würden Sie ein Thema für die Einstellungen in Ihrer Tätigkeit

<item name="preferenceTheme">@style/PreferenceThemeOverlay.v14.Material</item> 

Ich habe gegangen mit einem Material Design-Thema aus dem Xamarin.Android.Support.v14.Preference angeben müssen, aber man könnte auch eine von den anderen verwendet haben :

• @style/PreferenceThemeOverlay
• @style/PreferenceThemeOverlay.v14

Vollständige Details zu den Änderungen finden Sie unter pull request.