MvvmCross: How to navigate from regular view to Mv

问题:

I am slowly migrating my app over to MvvmCross on Android. I have not converted all Activities over to ViewModels yet. Therefore, I need to navigate from an Mvvm-controlled Activity to a regular Activity. To do this, I made my own Presenter and intercepted the Show method and did my own StartActivity. That seemed to work. However, now I need to go the other direction and have my regular Activity go back to the original Mvvm-controlled Activity. I tried just doing a StartActivity on the ViewModel using CLEAR_TOP flag, but I got an error:

"Null Extras seen on Intent when creating ViewModel - this should not happen - have you tried to navigate to an MvvmCross View directly?"

How can I go back to the original Mvvm-controlled activity from a regular Activity?

回答1:

Simple...

To go back from any standard Android Activity, you can simply ask the Activity to close using Finish()

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But beyond that...

If instead you want to go forwards to an MvvmCross View, then you need to know a little about MvvmCross internals: in particular about how MvvmCross navigation conceptually happens between ViewModels rather than between Activities, Pages or UIViewControllers.

If you want to go forwards to a new ViewModel, then you can do this using the IMvxViewDispatcher singleton - how to do this is shown in Show view from non-view/viewmodel in mvvmcross

If you then later want to go back from the current ViewModel, then you can try calling Close(this) within the ViewModel - by default, on Android this will map to Finish(), on Touch to PopViewController, on WpDev to GoBack()

回答2:

This seemed to work, but is a hack since I use a special string "MvxLaunchData".

Intent i = new Intent(this,typeof(LoginView));
i.AddFlags(ActivityFlags.ClearTop);
var converter = Mvx.Resolve<IMvxNavigationSerializer> ();
MvxViewModelRequest request = MvxViewModelRequest.GetDefaultRequest (typeof(LoginViewModel));
i.PutExtra ("MvxLaunchData", converter.Serializer.SerializeObject(request));
StartActivity(i);

I will try the method shown in the other question you referenced.