Custom fragment handling in MvvmCross and Xamarin

CustomFragmentsPresenter.cs

	public class CustomFragmentsPresenter : MvxFragmentsPresenter
	{
		public interface IMvxFragmentHostEx : IMvxFragmentHost
		{
			void Close(IMvxViewModel viewModel);
			void ChangePresentation (MvxPresentationHint hint);
		}

		private IMvxNavigationSerializer _serializer;

		private IMvxNavigationSerializer Serializer
		{
			get
			{
				if (_serializer != null)
					return _serializer;

				_serializer = Mvx.Resolve<IMvxNavigationSerializer>();
				return _serializer;
			}
		}

		public override void Show (MvxViewModelRequest request)
		{
			var fragmentHost = Activity as IMvxFragmentHost;
			if (fragmentHost != null) {
				var bundle = new Bundle ();
				var serializedRequest = Serializer.Serializer.SerializeObject (request);
				bundle.PutString (ViewModelRequestBundleKey, serializedRequest);
				fragmentHost.Show (request, bundle);
			}
			else
			{
				var bundle = new Bundle();
				var serializedRequest = Serializer.Serializer.SerializeObject(request);
				bundle.PutString(ViewModelRequestBundleKey, serializedRequest);

				var intentFor = new Intent (Activity.ApplicationContext, typeof(MainActivity));
				intentFor.PutExtra ("request", bundle);
				base.Show(intentFor);
			}
		}

		public override void ChangePresentation (MvxPresentationHint hint)
		{
			if (hint != null) {
				var fragmentHost = Activity as IMvxFragmentHost as IMvxFragmentHostEx;
				if (fragmentHost != null) {
					fragmentHost.ChangePresentation (hint);
				}
			}
			base.ChangePresentation (hint);
		}

		public override void Close (IMvxViewModel viewModel)
		{
			var fragmentHost = Activity as IMvxFragmentHost as IMvxFragmentHostEx;
			if (fragmentHost != null) {
				fragmentHost.Close (viewModel);
			}
			base.Close (viewModel);
		}

MainActivity.cs

[Activity(
		Label = "Menu",
		Theme = "@style/AppTheme",
		LaunchMode = LaunchMode.SingleTop,
		ConfigurationChanges = ConfigChanges.Orientation | ConfigChanges.ScreenSize
	)]
	public class MainActivity : MvxActionBarFragmentActivity, IMvxFragmentHost, CustomFragmentsPresenter.IMvxFragmentHostEx, FragmentManager.IOnBackStackChangedListener
	{
		public DrawerLayout drawerLayout;
		private MvxActionBarDrawerToggle drawerToggle;
		private FragmentManager fragmentManager;

		private IMvxNavigationSerializer _serializer;
		protected IMvxNavigationSerializer Serializer
		{
			get
			{
				if (_serializer != null)
					return _serializer;

				_serializer = Mvx.Resolve<IMvxNavigationSerializer>();
				return _serializer;
			}
		}

		protected override void OnCreate(Bundle bundle)
		{
			base.OnCreate(bundle);
			fragmentManager = FragmentManager;
			fragmentManager.AddOnBackStackChangedListener (this);

			SetContentView(Resource.Layout.activity_main);
			Toolbar toolbar = FindViewById<Toolbar>(Resource.Id.toolbar);
			if (toolbar != null)
			{
				SetSupportActionBar(toolbar);
				SupportActionBar.SetDisplayHomeAsUpEnabled(true);
			}

			drawerLayout = (DrawerLayout)FindViewById(Resource.Id.drawer);
			drawerToggle = new MvxActionBarDrawerToggle(
				this,                  /* host Activity */
				drawerLayout,         /* DrawerLayout object */
				toolbar,  /* nav drawer icon to replace 'Up' caret */
				Resource.String.drawer_open,  /* "open drawer" description */
				Resource.String.drawer_close  /* "close drawer" description */
			);

			drawerToggle.DrawerOpened += (o, args) =>
			{
				HideSoftKeyboard();
			};

			drawerLayout.SetDrawerListener(drawerToggle);

			Bundle request = Intent.GetBundleExtra ("request");
			var requestMain = new MvxViewModelRequest(typeof(MenuViewModel), null, null, null);
			Show(requestMain, request);

			if (request != null) {
				var deserializedRequest = Serializer.Serializer.DeserializeObject<MvxViewModelRequest>(request.GetString(CustomFragmentsPresenter.ViewModelRequestBundleKey));
				Show (deserializedRequest, request);
			}
		}

		public override void OnBackPressed ()
		{
			//TODO: This is a fix to get the back button working. Don't know if it is a good one.
			var currentFragment = fragmentManager.FindFragmentById(Resource.Id.content_frame) as MvxFragment;
			if (currentFragment != null && fragmentManager.BackStackEntryCount > 1) {
				fragmentManager.PopBackStackImmediate ();
				return;
			} else if (drawerLayout.IsDrawerOpen (GravityCompat.Start))
				drawerLayout.CloseDrawers ();
			else
				base.OnBackPressed ();
		}

		public override void OnConfigurationChanged(Configuration newConfig)
		{
			base.OnConfigurationChanged(newConfig);
			drawerToggle.OnConfigurationChanged(newConfig);
		}

		protected override void OnPostCreate(Bundle savedInstanceState)
		{
			base.OnPostCreate(savedInstanceState);
			drawerToggle.SyncState();
		}

		public void HideSoftKeyboard()
		{
			InputMethodManager manager = (InputMethodManager)GetSystemService(Context.InputMethodService);
			manager.HideSoftInputFromWindow(CurrentFocus.WindowToken, 0);
		}

		public void ShowSoftKeyboard()
		{
			InputMethodManager manager = (InputMethodManager)GetSystemService(Context.InputMethodService);
			manager.ShowSoftInputFromInputMethod(CurrentFocus.WindowToken, 0);
		}

		public bool Show (MvxViewModelRequest request, Bundle bundle)
		{
			if (request.ViewModelType == typeof(MenuViewModel)) {
				ShowFragment (request, Resource.Id.left_drawer, bundle);
				return true;
			}
			else if (request.ViewModelType == typeof(MiniPlayerViewModel))
			{
				ShowFragment(request, Resource.Id.player_frame, bundle);
				return true;
			}
			else if (request.ViewModelType == typeof(LoginViewModel))
			{
				ChangePresentation(new ClearNavBackStackHint());
				ShowFragment(request, Resource.Id.content_frame, bundle);
				return true;
			}
			else {
				ShowFragment(request, Resource.Id.content_frame, bundle, true);
				return true;
			}
		}

		public void ShowFragment(MvxViewModelRequest request, int contentId, Bundle bundle = null, bool addToBackStack = false)
		{
			MvxFragment fragment = null;

			IMvxViewsContainer viewContainer = Mvx.Resolve<IMvxViewsContainer>();
			Type viewType = viewContainer.GetViewType(request.ViewModelType);

			Fragment currentContentFragment = FragmentManager.FindFragmentById(contentId);
			if (currentContentFragment != null && currentContentFragment.GetType () == viewType && (request.ParameterValues == null || (request.ParameterValues != null && request.ParameterValues.Count == 0))) {
				drawerLayout.CloseDrawers();
				return;
			}
			SupportActionBar.Show();
			drawerLayout.SetDrawerLockMode(DrawerLayout.LockModeUnlocked);

			fragment = (MvxFragment)Activator.CreateInstance(viewType);

			var loaderService = Mvx.Resolve<IMvxViewModelLoader>();
			var viewModel = loaderService.LoadViewModel(request, null);
			fragment.ViewModel = viewModel;

			var contentManager = fragmentManager.BeginTransaction();
			contentManager.Replace(contentId, fragment);
			if(addToBackStack)
				contentManager.AddToBackStack(fragment.GetType().Name);
			contentManager.Commit();

			drawerLayout.CloseDrawers();
		}

		public void OnBackStackChanged ()
		{
			Fragment currentPlayerFragment = fragmentManager.FindFragmentById(Resource.Id.player_frame);
			Fragment currentContentFragment = FragmentManager.FindFragmentById (Resource.Id.content_frame);
			if (currentPlayerFragment != null && currentContentFragment != null) {
				var contentManager = fragmentManager.BeginTransaction();
				if (currentContentFragment.GetType () == typeof(PlayerFragment) || currentContentFragment.GetType () == typeof(QueueFragment) || currentContentFragment.GetType () == typeof(LoginFragment))
					contentManager.Hide (currentPlayerFragment);
				else
					contentManager.Show (currentPlayerFragment);
				contentManager.Commit ();
			}
		}

		public void ChangePresentation (MvxPresentationHint hint)
		{
			//TODO: Ignore this on Android for now
			//if (hint is ClearNavBackStackHint)
			//fragmentManager.PopBackStackImmediate(null, PopBackStackFlags.Inclusive);
		}

		public void Close (IMvxViewModel viewModel)
		{
			var currentFragment = fragmentManager.FindFragmentById (Resource.Id.content_frame) as MvxFragment;
			if (currentFragment != null && currentFragment.ViewModel == viewModel) {
				fragmentManager.PopBackStackImmediate ();
				return;
			}
		}

MvxActionBarDrawerToggle.cs

	public class ActionBarDrawerEventArgs : EventArgs
	{
		public View DrawerView { get; set; }

		public float SlideOffset { get; set; }

		public int NewState { get; set; }
	}

	public delegate void ActionBarDrawerChangedEventHandler(object s, ActionBarDrawerEventArgs e);

	public class MvxActionBarDrawerToggle : Android.Support.V7.App.ActionBarDrawerToggle
	{
		public MvxActionBarDrawerToggle(Activity activity,
			DrawerLayout drawerLayout,
			int openDrawerContentDescRes,
			int closeDrawerContentDescRes)
			: base(activity,
				drawerLayout,
				openDrawerContentDescRes,
				closeDrawerContentDescRes)
		{
		}

		public MvxActionBarDrawerToggle(Activity activity,
			DrawerLayout drawerLayout,
			Toolbar toolbar,
			int openDrawerContentDescRes,
			int closeDrawerContentDescRes)
			: base(activity,
				drawerLayout,
				toolbar,
				openDrawerContentDescRes,
				closeDrawerContentDescRes)
		{
		}

		public event ActionBarDrawerChangedEventHandler DrawerClosed;

		public event ActionBarDrawerChangedEventHandler DrawerOpened;

		public event ActionBarDrawerChangedEventHandler DrawerSlide;

		public event ActionBarDrawerChangedEventHandler DrawerStateChanged;

		public override void OnDrawerClosed(View drawerView)
		{
			if (null != this.DrawerClosed)
				this.DrawerClosed(this, new ActionBarDrawerEventArgs { DrawerView = drawerView });
			base.OnDrawerClosed(drawerView);
		}

		public override void OnDrawerOpened(View drawerView)
		{
			if (null != this.DrawerOpened)
				this.DrawerOpened(this, new ActionBarDrawerEventArgs { DrawerView = drawerView });
			base.OnDrawerOpened(drawerView);
		}

		public override void OnDrawerSlide(View drawerView, float slideOffset)
		{
			if (null != this.DrawerSlide)
				this.DrawerSlide(this, new ActionBarDrawerEventArgs
					{
						DrawerView = drawerView,
						SlideOffset = slideOffset
					});
			base.OnDrawerSlide(drawerView, slideOffset);
		}

		public override void OnDrawerStateChanged(int newState)
		{
			if (null != this.DrawerStateChanged)
				this.DrawerStateChanged(this, new ActionBarDrawerEventArgs
					{
						NewState = newState
					});
			base.OnDrawerStateChanged(newState);
		}
	}