TabHost pass Parameter in CreateIntentFor<>

Question

After downloading the newest Version of mvvmcross (V3) I had some work to do, to upgrade some of my projects to the new state. Last thing I'm not able to fulfill is to pass a parameter to the viewmodel from the tabhost. In the older versions it worked fine (but it was different) and now I got an error.

But First here the Code (Line 19 makes trouble (watch comment in code), Line 18 works but only without Parameters):

[Activity]
public class MainActivity : MvxTabActivity
{
    public new MainViewModel ViewModel
    {
        get { return (MainViewModel)base.ViewModel; }
        set { base.ViewModel = value; }
    }

    protected override void OnViewModelSet()
    {
        SetContentView(Resource.Layout.Main);

        TabHost.TabSpec spec;
        Intent intent;

        spec = TabHost.NewTabSpec("listeaktiv");
        spec.SetIndicator(App.indicatorActive, Resources.GetDrawable(Resource.Drawable.green));
        //spec.SetContent(this.CreateIntentFor(ViewModel.ListViewModel)); -> It works (But only without Parameters! How could I pass them here?)
        spec.SetContent(this.CreateIntentFor<ListViewModel>(new { parameter = App.indicatorActive })); //Exception (on the next Line)
        TabHost.AddTab(spec);
    }

    protected override void OnCreate(Bundle bundle)
    {
        base.OnCreate(bundle);
    }
}

(App.indicatorActive is the Parameter I want to pass, its in the App.cs: (public static string indicatorActive = "Active";)

My ListViewModel looks like that:

public class ListViewModel : BaseViewModel
{
        public ListViewModel(string parameter)
        {

        }
}

Error:

Unhandled Exception:
Cirrious.CrossCore.Exceptions.MvxException: Failed to load ViewModel for type 
INApplikationsMonitor.Core.ViewModels.ListViewModel from locator MvxDefaultViewModelLocator

Answer 1

My guess is that this is just because you are using the old ViewModel lifecycle.

In v3:

• the ViewModel constructor parameters are used for IoC - for Dependency Injection of services.
• for passing parameters you need to instead use an Init method within the ViewModel

For more on this, see: http://slodge.blogspot.co.uk/2013/03/v3-new-viewmodel-lifecycle.html :

The default ViewModelLocator in v3 builds new ViewModel instances using a 4-step process - CIRS:

• Construction - using IoC for Dependency Injection
• Init() - initialisation of navigation parameters
• ReloadState() - rehydration after tombstoning
• Start() - called when initialisation and rehydration are complete