I have the following problem when using fragments in mvvmCross. I borrowed the code from https://github.com/slodge/MvvmCross-Tutorials/tree/master/Fragments. The Framepresenter Class which is in https://github.com/slodge/MvvmCross-Tutorials/blob/master/Fragments/FragmentSample.UI.Droid/Setup.cs resolved requests to show viewmodels in the show method
public class CustomPresenter : MvxAndroidViewPresenter , ICustomPresenter { private Dictionary _dictionary = new Dictionary(); public override void Show(MvxViewModelRequest request) { IFragmentHost host; if (_dictionary.TryGetValue(request.ViewModelType, out host)) { if (host.Show(request)) { return; } } base.Show(request); } ...
In the first run all works well. If I close the app with the "Back" Button of android and open it again I will get a null pointer exception in the Show method of the base class (MvxAndroidViewPresenter). This is because the top level activity does not exist any more. The property Activity in MvxAndroidViewPresenter is returning null. How can I recreate the top level activity when restarting the app?
I get the following exception
06-26 16:06:28.102 I/MonoDroid( 6791): UNHANDLED EXCEPTION: System.NullReferenceException: Object reference not set to an instance of an object 06-26 16:06:28.102 I/MonoDroid( 6791): at Cirrious.MvvmCross.Droid.Views.MvxAndroidViewPresenter.Show (Cirrious.MvvmCross.ViewModels.MvxViewModelRequest) [0x0000f] in d:\Projekte\MvvmCross\mvvmcross-20130621\Cirrious\Cirrious.MvvmCross.Droid\Views\MvxAndroidViewPresenter.cs:29 06-26 16:06:28.102 I/MonoDroid( 6791): at ManCockpit.UI.Droid.CockpitFragmentPresenter.Show (Cirrious.MvvmCross.ViewModels.MvxViewModelRequest) [0x00040] in d:\Projekte\ManCockpitV2\ManCockpit.UI.Droid\CockpitFragmentPresenter.cs:41 06-26 16:06:28.102 I/MonoDroid( 6791): at Cirrious.MvvmCross.Droid.Views.MvxAndroidViewDispatcher/c__DisplayClass1.b__0 () [0x00000] in d:\Projekte\MvvmCross\mvvmcross-20130621\Cirrious\Cirrious.MvvmCross.Droid\Views\MvxAndroidViewDispatcher.cs:27 06-26 16:06:28.102 I/MonoDroid( 6791): at Cirrious.MvvmCross.Droid.Views.MvxAndroidViewDispatcher.ShowViewModel (Cirrious.MvvmCross.ViewModels.MvxViewModelRequest) [0x00015] in d:\Projekte\MvvmCross\mvvmcross-20130621\Cirrious\Cirrious.MvvmCross.Droid\Views\MvxAndroidViewDispatcher.cs:27 06-26 16:06:28.102 I/MonoDroid( 6791): at Cirrious.MvvmCross.ViewModels.MvxNavigatingObject.ShowViewModelImpl (System.Type,Cirrious.MvvmCross.ViewModels.IMvxBundle,Cirrious.MvvmCross.ViewModels.IMvxBundle,Cirrious.MvvmCross.ViewModels.MvxRequestedBy) 06-26 16:06:28.102 I/MonoDroid( 6791): at (wrapper dynamic-method) objec06-26 16:06:28.102 I/MonoDroid( 6791): at Cirrious.MvvmCross.ViewModels.MvxNavigatingObject.ShowViewModel (System.Type,Cirrious.MvvmCross.ViewModels.IMvxBundle,Cirrious.MvvmCross.ViewModels.IMvxBundle,Cirrious.MvvmCross.ViewModels.MvxRequestedBy) 06-26 16:06:28.102 I/MonoDroid( 6791): at Cirrious.MvvmCross.ViewModels.MvxNavigatingObject.ShowViewModel (Cirrious.MvvmCross.ViewModels.IMvxBundle,Cirrious.MvvmCross.ViewModels.MvxBundle,Cirrious.MvvmCross.ViewModels.MvxRequestedBy) 06-26 16:06:28.102 I/MonoDroid( 6791): at Cirrious.MvvmCross.ViewModels.MvxAppStart`1.Start (object) 06-26 16:06:28.102 I/MonoDroid( 6791): at Cirrious.MvvmCross.Droid.Views.MvxSplashScreenActivity.TriggerFirstNavigate () [0x00007] in d:\Projekte\MvvmCross\mvvmcross-20130621\Cirrious\Cirrious.MvvmCross.Droid\Views\MvxSplashScreenActivity.cs:82 06-26 16:06:28.102 I/MonoDroid( 6791): at Cirrious.MvvmCross.Droid.Views.MvxSplashScreenActivity.InitializationComplete () [0x00001] in d:\Projekte\MvvmCross\mvvmcross-20130621\Cirrious\Cirrious.MvvmCross.Droid\Views\MvxSplashScreenActivity.cs:76 06-26 16:06:28.102 I/MonoDroid( 6791): at Cirrious.MvvmCross.Droid.Platform.MvxAndroidSetupSingleton.InitialiseFromSplashScreen (Cirrious.MvvmCross.Droid.Views.IMvxAndroidSplashScreenActivity) [0x00036] in d:\Projekte\MvvmCross\mvvmcross-20130621\Cirrious\Cirrious.MvvmCross.Droid\Platform\MvxAndroidSetupSingleton.cs:76 06-26 16:06:28.102 I/MonoDroid( 6791): at Cirrious.MvvmCross.Droid.Views.MvxSplashScreenActivity.OnCreate (Android.OS.Bundle) [0x00014] in d:\Projekte\MvvmCross\mvvmcross-20130621\Cirrious\Cirrious.MvvmCross.Droid\Views\MvxSplashScreenActivity.cs:47 06-26 16:06:28.102 I/MonoDroid( 6791): at ManCockpit.UI.Droid.SplashScreenActivity.OnCreate (Android.OS.Bundle) [0x0002e] in d:\Projekte\ManCockpitV2\ManCockpit.UI.Droid\SplashScreenActivity.cs:105 06-26 16:06:28.102 I/MonoDroid( 6791): at Android.App.Activity.n_OnCreate_Landroid_os_Bundle_ (intptr,intptr,intptr) [0x00010] in /Users/builder/data/lanes/monodroid-lion-bs1/0cc7ae3b/source/monodroid/src/Mono.Android/platforms/android-15/src/generated/Android.App.Activity.cs:1859 06-26 16:06:28.102 I/MonoDroid( 6791): at (wrapper dynamic-method) object.08473369-0d89-4344-a57c-40e97793bab8 (intptr,intptr,intptr)