A Comprehensive Guide to Creating a Xamarin.Forms App with MvvmCross (Part 3 of 5)

public interface IMvxPageNavigationProvider
{
	void Push(Page page);
	void Pop();
}

public interface IMvxPageNavigationHost
{
	IMvxPageNavigationProvider NavigationProvider { get; set; }
}

public sealed class MvxPagePresenter
		: MvxAndroidViewPresenter, IMvxPageNavigationHost
{
	public override void Show(MvxViewModelRequest request)
	{
		if (TryShowPage(request))
			return;

		Mvx.Error("Skipping request for {0}", request.ViewModelType.Name);
	}

	private bool TryShowPage(MvxViewModelRequest request)
	{
		if (this.NavigationProvider == null)
			return false;

		var page = MvxPresenterHelpers.CreatePage<Page>(request);
		if (page == null)
			return false;

		var viewModel = MvxPresenterHelpers.LoadViewModel(request);

		page.BindingContext = viewModel;

		this.NavigationProvider.Push(page);

		return true;
	}

	public override void Close(IMvxViewModel viewModel)
	{
		if (this.NavigationProvider == null)
			return;

		this.NavigationProvider.Pop();
	}

	public IMvxPageNavigationProvider NavigationProvider { get; set; }
}

protected override IMvxAndroidViewPresenter CreateViewPresenter()
{
	var presenter = new MvxPagePresenter();
	Mvx.RegisterSingleton<IMvxPageNavigationHost>(presenter);
	return presenter;
}

public interface IUiContext
{
	object CurrentContext { get; set; }
}

public interface IUiContext
{
#if ANDROID
	Android.App.Activity CurrentContext { get; set; }
#elif IOS
       	UIKit.UIViewController CurrentContext { get; set; }
#endif
}

public class UiContext : IUiContext
{
	public object CurrentContext { get; set; }
}

public class UiContext : IUiContext
{
#if ANDROID
       	public Android.App.Activity CurrentContext { get; set; }
#elif IOS
	public UIKit.UIViewController CurrentContext { get; set; }
#endif
}

[Activity(Label = "XFormsCross Template",
	ConfigurationChanges = ConfigChanges.ScreenSize | ConfigChanges.Orientation)]
public class MvxNavigationActivity
	: FormsApplicationActivity, IMvxPageNavigationProvider
{
	protected override void OnCreate(Bundle bundle)
	{
		base.OnCreate(bundle);
		Xamarin.Forms.Forms.Init(this, bundle);

		var uiContext = new UiContext
		{
			CurrentContext = this
		};

		Mvx.Resolve<IMvxPageNavigationHost>().NavigationProvider = this;
		Mvx.Resolve<IMvxAppStart>().Start();
	}

	public async void Push(Page page)
	{
		if (MvxNavigationActivity.NavigationPage != null)
		{
			await MvxNavigationActivity.NavigationPage.PushAsync(page);
			return;
		}

		MvxNavigationActivity.NavigationPage = new NavigationPage(page);
		this.SetPage(MvxNavigationActivity.NavigationPage);
	}

	public async void Pop()
	{
		if (MvxNavigationActivity.NavigationPage == null)
			return;

		await MvxNavigationActivity.NavigationPage.PopAsync();
	}

	public static NavigationPage NavigationPage { get; set; }
}

public override void InitializationComplete()
{
	StartActivity(typeof(MvxNavigationActivity));
}