Ich habe eine Xamarin Forms-App, die derzeit für Android erstellt wird. Ich habe einMainActivity das verwendet, um @ zu verlängeFormsApplicationActivity, aber da ich ein benutzerdefiniertes Design verwenden wollte, musste ich es ändern, um @ zu erweiteFormsAppCompatActivity (siehe meine andere Frage:Xamarin Forms benutzerdefiniertes Design funktioniert nicht).

mmer seit dem Wechsel vonFormsApplicationActivity zuFormsAppCompatActivity Die App stürzt ab, wenn ich die App verlasse und dann wieder in die App wechsle. Es wirft einen Fehler imApp.xaml.cs Klasse in derOnResume -Methode, bei der ich versuche, die Hauptseite auf eine neue Navigationsseite zu setzen:

protected override void OnResume()
{
    bool isRegistered = _authenticationService.IsRegistered();

    MainPage = isRegistered 
        ? new NavigationPage(new LoginPage()) 
        : new NavigationPage(new RegisterPage()); // this results in the crash
}

Der Fehler, den ich erhalte, ist:

Java.Lang.IllegalStateException: Diese Aktion kann nach onSaveInstanceState @ nicht ausgeführt werde

Dies ist der Stacktrace:

03-09 13:43:52.098 I/MonoDroid( 1243): Java.Lang.IllegalStateException: Can not perform this action after onSaveInstanceState
03-09 13:43:52.098 I/MonoDroid( 1243):   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw () [0x0000c] in /Users/builder/data/lanes/2098/3efa14c4/source/mono/external/referencesource/mscorlib/system/runtime/exceptionservices/exceptionservicescommon.cs:143 
03-09 13:43:52.098 I/MonoDroid( 1243):   at Android.Runtime.JNIEnv.CallIntMethod (IntPtr jobject, IntPtr jmethod) [0x00063] in /Users/builder/data/lanes/2098/3efa14c4/source/monodroid/src/Mono.Android/src/Runtime/JNIEnv.g.cs:386 
03-09 13:43:52.098 I/MonoDroid( 1243):   at Android.Support.V4.App.FragmentTransactionInvoker.Commit () [0x00033] in <filename unknown>:0 
03-09 13:43:52.098 I/MonoDroid( 1243):   at Xamarin.Forms.Platform.Android.AppCompat.NavigationPageRenderer.SwitchContentAsync (Xamarin.Forms.Page view, Boolean animated, Boolean removed, Boolean popToRoot) [0x000e1] in <filename unknown>:0 
03-09 13:43:52.098 I/MonoDroid( 1243):   at Xamarin.Forms.Platform.Android.AppCompat.NavigationPageRenderer.OnPushAsync (Xamarin.Forms.Page view, Boolean animated) [0x00000] in <filename unknown>:0 
03-09 13:43:52.098 I/MonoDroid( 1243):   at Xamarin.Forms.Platform.Android.AppCompat.NavigationPageRenderer.PushViewAsync (Xamarin.Forms.Page page, Boolean animated) [0x00000] in <filename unknown>:0 
03-09 13:43:52.098 I/MonoDroid( 1243):   at Xamarin.Forms.Platform.Android.AppCompat.NavigationPageRenderer.<OnElementChanged>b__13_0 (Xamarin.Forms.Page p) [0x00000] in <filename unknown>:0 
03-09 13:43:52.098 I/MonoDroid( 1243):   at Xamarin.Forms.EnumerableExtensions.ForEach[T] (IEnumerable`1 enumeration, System.Action`1 action) [0x00010] in <filename unknown>:0 
03-09 13:43:52.098 I/MonoDroid( 1243):   at Xamarin.Forms.Platform.Android.AppCompat.NavigationPageRenderer.OnElementChanged (Xamarin.Forms.Platform.Android.ElementChangedEventArgs`1 e) [0x001af] in <filename unknown>:0 
03-09 13:43:52.098 I/MonoDroid( 1243):   at Xamarin.Forms.Platform.Android.VisualElementRenderer`1[TElement].SetElement (Xamarin.Forms.Platform.Android.TElement element) [0x000fc] in <filename unknown>:0 
03-09 13:43:52.098 I/MonoDroid( 1243):   at Xamarin.Forms.Platform.Android.VisualElementRenderer`1[TElement].Xamarin.Forms.Platform.Android.IVisualElementRenderer.SetElement (Xamarin.Forms.VisualElement element) [0x00027] in <filename unknown>:0 
03-09 13:43:52.098 I/MonoDroid( 1243):   at Xamarin.Forms.Platform.Android.Platform.CreateRenderer (Xamarin.Forms.VisualElement element) [0x0001f] in <filename unknown>:0 
03-09 13:43:52.098 I/MonoDroid( 1243):   at Xamarin.Forms.Platform.Android.RendererFactory.GetRenderer (Xamarin.Forms.VisualElement view) [0x00000] in <filename unknown>:0 
03-09 13:43:52.098 I/MonoDroid( 1243):   at Xamarin.Forms.Platform.Android.AppCompat.Platform.AddChild (Xamarin.Forms.Page page, Boolean layout) [0x00015] in <filename unknown>:0 
03-09 13:43:52.098 I/MonoDroid( 1243):   at Xamarin.Forms.Platform.Android.AppCompat.Platform.SetPage (Xamarin.Forms.Page newRoot) [0x00090] in <filename unknown>:0 
03-09 13:43:52.098 I/MonoDroid( 1243):   at Xamarin.Forms.Platform.Android.FormsAppCompatActivity.InternalSetPage (Xamarin.Forms.Page page) [0x0001a] in <filename unknown>:0 
03-09 13:43:52.098 I/MonoDroid( 1243):   at Xamarin.Forms.Platform.Android.FormsAppCompatActivity.AppOnPropertyChanged (System.Object sender, System.ComponentModel.PropertyChangedEventArgs args) [0x0001e] in <filename unknown>:0 
03-09 13:43:52.098 I/MonoDroid( 1243):   at Xamarin.Forms.BindableObject.OnPropertyChanged (System.String propertyName) [0x00012] in <filename unknown>:0 
03-09 13:43:52.098 I/MonoDroid( 1243):   at Xamarin.Forms.Application.set_MainPage (Xamarin.Forms.Page value) [0x0008b] in <filename unknown>:0 
03-09 13:43:52.098 I/MonoDroid( 1243):   at Smartbit.App.OnResume () [0x00020] in C:\Users\leonc\Documents\Visual Studio 2015\Projects\Smartbit\Smartbit\Smartbit\App.xaml.cs:52 
03-09 13:43:52.098 I/MonoDroid( 1243):   at Xamarin.Forms.Application.SendResume () [0x00006] in <filename unknown>:0 
03-09 13:43:52.098 I/MonoDroid( 1243):   at Xamarin.Forms.Platform.Android.FormsAppCompatActivity.OnStateChanged () [0x00039] in <filename unknown>:0 
03-09 13:43:52.098 I/MonoDroid( 1243):   at Xamarin.Forms.Platform.Android.FormsAppCompatActivity.OnRestart () [0x00019] in <filename unknown>:0 
03-09 13:43:52.098 I/MonoDroid( 1243):   at Android.App.Activity.n_OnRestart (IntPtr jnienv, IntPtr na,tive__this) [0x00009] in /Users/builder/data/lanes/2098/3efa14c4/source/monodroid/src/Mono.Android/platforms/android-23/src/generated/Android.App.Activity.cs:4539 
03-09 13:43:52.098 I/MonoDroid( 1243):   at (wrapper dynamic-method) System.Object:cba7a870-1435-4f70-9059-e10915aba0c0 (intptr,intptr)
03-09 13:43:52.098 I/MonoDroid( 1243):   --- End of managed exception stack trace ---
03-09 13:43:52.098 I/MonoDroid( 1243): java.lang.IllegalStateException: Can not perform this action after onSaveInstanceState
03-09 13:43:52.098 I/MonoDroid( 1243):  at android.support.v4.app.FragmentManagerImpl.checkStateLoss(FragmentManager.java:1448)
03-09 13:43:52.098 I/MonoDroid( 1243):  at android.support.v4.app.FragmentManagerImpl.enqueueAction(FragmentManager.java:1466)
03-09 13:43:52.098 I/MonoDroid( 1243):  at android.support.v4.app.BackStackRecord.commitInternal(BackStackRecord.java:634)
03-09 13:43:52.098 I/MonoDroid( 1243):  at android.support.v4.app.BackStackRecord.commit(BackStackRecord.java:613)
03-09 13:43:52.098 I/MonoDroid( 1243):  at md5b60ffeb829f638581ab2bb9b1a7f4f3f.FormsAppCompatActivity.n_onRestart(Native Method)
03-09 13:43:52.098 I/MonoDroid( 1243):  at md5b60ffeb829f638581ab2bb9b1a7f4f3f.FormsAppCompatActivity.onRestart(FormsAppCompatActivity.java:86)
03-09 13:43:52.098 I/MonoDroid( 1243):  at android.app.Instrumentation.callActivityOnRestart(Instrumentation.java:1181)
03-09 13:43:52.098 I/MonoDroid( 1243):  at android.app.Activity.performRestart(Activity.java:5291)
03-09 13:43:52.098 I/MonoDroid( 1243):  at android.app.Activity.performResume(Activity.java:5302)
03-09 13:43:52.098 I/MonoDroid( 1243):  at android.app.ActivityThread.performResumeActivity(ActivityThread.java:2764)
03-09 13:43:52.098 I/MonoDroid( 1243):  at android.app.ActivityThread.handleResumeActivity(ActivityThread.java:2803)
03-09 13:43:52.098 I/MonoDroid( 1243):  at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1238)
03-09 13:43:52.098 I/MonoDroid( 1243):  at android.os.Handler.dispatchMessage(Handler.java:102)
03-09 13:43:52.098 I/MonoDroid( 1243):  at android.os.Looper.loop(Looper.java:136)
03-09 13:43:52.098 I/MonoDroid( 1243):  at android.app.ActivityThread.main(ActivityThread.java:5001)
03-09 13:43:52.098 I/MonoDroid( 1243):  at java.lang.reflect.Method.invokeNative(Native Method)
03-09 13:43:52.098 I/MonoDroid( 1243):  at java.lang.reflect.Method.invoke(Method.java:515)
03-09 13:43:52.098 I/MonoDroid( 1243):  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:785)
03-09 13:43:52.098 I/MonoDroid( 1243):  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:601)
03-09 13:43:52.098 I/MonoDroid( 1243):  at dalvik.system.NativeStart.main(Native Method)