Tab Handling in Mvvmcross with MvxTabsFragmentActivity and MvxCachingFragmentStatePagerAdapter - tabs

Question

I am writing an Android app with a tab. I was following the old method in the sample "FragmentSample". It was working fine but I am evaluating to switch to viewpager.
In FragmentSample:
TabViewModel creates an instance of viewmodel for each individual tab
(Vm1, Vm2...).
In TabView, each tab fragment (Tab1Fragment,
Tab2Fragment...) are explicitly associated to the viewmodel (Vm1,
Vm2...) created in TabViewModel.
It is perfect as I could do some navigation initialization to Vm1,
Vm2 in TabViewModel.
public class TabViewModel : BaseViewModel
{
public TabViewModel()
{
Vm1 = Mvx.IocConstruct<FirstTabViewModel>();
Vm2 = Mvx.IocConstruct<SecondTabViewModel>();
Vm3 = Mvx.IocConstruct<ThirdTabViewModel>();
}
public BaseViewModel Vm1 { get; set; }
public BaseViewModel Vm2 { get; set; }
public BaseViewModel Vm3 { get; set; }
}
public class TabView : MvxTabsFragmentActivity
{
public TabViewModel TabViewModel
{
get { return (TabViewModel)base.ViewModel; }
}
public TabView()
: base(Resource.Layout.Page_TabView, Resource.Id.actualtabcontent)
{
}
protected override void AddTabs(Bundle args)
{
AddTab<Tab1Fragment>("Tab1", "Tab 1", args, TabViewModel.Vm1);
AddTab<Tab2Fragment>("Tab2", "Tab 2", args, TabViewModel.Vm2);
// note that
AddTab<Tab3Fragment>("Tab3.1", "Tab 3.1", args, TabViewModel.Vm3);
AddTab<Tab3Fragment>("Tab3.2", "Tab 3.2", args, TabViewModel.Vm3);
AddTab<Tab3BigFragment>("Tab3.3", "Tab 3.3", args, TabViewModel.Vm3);
}
}
In the latest sample project "Example" in MvvmCross-All:
ExampleViewPagerStateViewModel create an instance of RecyclerViewModel
ExampleViewPagerStateFragment defines the tabs (RecyclerView
1...5) with MvxCachingFragmentStatePagerAdapter.
When MvxCachingFragmentStatePagerAdapter is executed, another
instance of RecyclerViewModel will be created
RecyclerViewModel created in ExampleViewPagerStateViewModel seems to
be completely irrelevant to the tab built. I commented out the
creation in ExampleViewPagerStateViewModel and there was no change to
the app behavior.
RecyclerViewModel was created twice. It is the same in
ExampleViewPagerFragment in the same project, and in the old version
of this sample XPlatformMenus.
public class ExampleViewPagerStateViewModel
: MvxViewModel
{
public RecyclerViewModel Recycler { get; private set; }
public ExampleViewPagerStateViewModel()
{
Recycler = new RecyclerViewModel();
}
}
public class ExampleViewPagerStateFragment : BaseStateFragment<ExampleViewPagerStateViewModel>
{
protected override int FragmentId => Resource.Layout.fragment_example_viewpager_state;
public override View OnCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState)
{
var view = base.OnCreateView(inflater, container, savedInstanceState);
var viewPager = view.FindViewById<ViewPager>(Resource.Id.viewpager);
if (viewPager != null)
{
var fragments = new List<MvxCachingFragmentStatePagerAdapter.FragmentInfo>
{
//new MvxCachingFragmentStatePagerAdapter.FragmentInfo("RecyclerView 1", typeof (RecyclerViewFragment),
// typeof (RecyclerViewModel)),
//new MvxCachingFragmentStatePagerAdapter.FragmentInfo("RecyclerView 2", typeof (RecyclerViewFragment),
// typeof (RecyclerViewModel)),
//new MvxCachingFragmentStatePagerAdapter.FragmentInfo("RecyclerView 3", typeof (RecyclerViewFragment),
// typeof (RecyclerViewModel)),
//new MvxCachingFragmentStatePagerAdapter.FragmentInfo("RecyclerView 4", typeof (RecyclerViewFragment),
// typeof (RecyclerViewModel)),
new MvxCachingFragmentStatePagerAdapter.FragmentInfo("RecyclerView 5", typeof (RecyclerViewFragment),
typeof (RecyclerViewModel))
};
viewPager.Adapter = new MvxCachingFragmentStatePagerAdapter(Activity, ChildFragmentManager, fragments);
}
var tabLayout = view.FindViewById<TabLayout>(Resource.Id.tabs);
tabLayout.SetupWithViewPager(viewPager);
return view;
}
}
My questions are:
What is the usage of creating RecyclerViewModel in
ExampleViewPagerStateViewModel in "Example"?
In FragmentSample, Tab3.1 Tab3.2 Tab3.3 are sharing the same Vm3. Can
I do the same thing with ViewPager? Is there any way I can specify
the tab view (RecyclerView 1...5) to associate to the
RecyclerViewModel created in ExampleViewPagerStateViewModel but not a
new instance?
Thanks.

Answer 1

Just found that it could be done by changing the third parameter of FragmentInfo to Recycler created in RecyclerViewModel. The sample should make the change.