MVP pattern in MonoDroid

gistfile1.cs

    public interface IMainView
    {
        void RefreshList(IList<string> portfolioNames);
        void StartAddPortfolioActivity();
        void StartViewPortfolioActivity(long portfolioId);
        void StartEditPortfolioActivity(int itemId);
        void StartConfigActivity();
        void ExitApplication();
    }

    public interface IMainPresenter
    {
        void Initialize(IMainView view);
        void RefreshPortfolioList();
        void AddNewPortfolio();
        void ViewPortfolio(int portfolioPosition);
        void DeletePortfolio(int itemId);
        void EditPortfolio(int itemId);
        void GotoConfig();
        void ExitApplication();
        int GetPortfolioIdForContextMenu(string selectedPortfolioName);
    }


    public class MainPresenter : IMainPresenter
    {
        private IPortfolioRepository _repo;

        private IMainView _currentView;

        private IList<Portfolio> _portfolios;
        private IList<Portfolio> Portfolios
        {
            get
            {
                return _portfolios ?? (_portfolios = _repo.GetAllPortfolios());
            }
        }

        public MainPresenter(IPortfolioRepository portfolioRepository)
        {
            _repo = portfolioRepository;
        }

        public void Initialize(IMainView view)
        {
            _currentView = view;
            RefreshPortfolioList();
        }

        public void RefreshPortfolioList()
        {
            var portfolioNames = Portfolios.Select(p => p.Name).ToList();
            _currentView.RefreshList(portfolioNames);
        }

        public void AddNewPortfolio()
        {
            _currentView.StartAddPortfolioActivity();
        }

        public void ViewPortfolio(int portfolioPosition)
        {
            // why is _currentView null?
            _currentView.StartViewPortfolioActivity(Portfolios[portfolioPosition].ID ?? -1);
        }

        public void DeletePortfolio(int itemId)
        {
            _repo.DeletePortfolioById(itemId);
        }

        public void EditPortfolio(int itemId)
        {
            _currentView.StartEditPortfolioActivity(itemId);
        }

        public void GotoConfig()
        {
            _currentView.StartConfigActivity();
        }

        public void ExitApplication()
        {
            _currentView.ExitApplication();
        }

        public int GetPortfolioIdForContextMenu(string selectedPortfolioName)
        {
            var selectedPortfolio = _repo.GetPortfolioByName(selectedPortfolioName);
            var id = (int)(selectedPortfolio.ID ?? -1);
            return id;
        }
    }


    [Activity(Label = "Stock Portfolio", MainLauncher = true, Icon = "@drawable/icon")]
    public class MainActivity : Activity, IMainView
    {
        [LazyView(Resource.Id.btnAddPortfolio)] protected Button AddPortfolioButton;
        [LazyView(Resource.Id.portfolioList)] protected ListView PortfolioListView;

        [IoC] IMainPresenter _presenter;

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

            SetContentView(Resource.Layout.main);

            _presenter.Initialize(this);

            WireUpEvents();
        }

        #region IMainView implementation

        public void RefreshList(IList<string> portfolioNames)
        {
            var listAdapter = new ArrayAdapter<string>(this, Android.Resource.Layout.SimpleListItem1, portfolioNames);
            PortfolioListView.Adapter = listAdapter;
        }

        public void ExitApplication()
        {
            Finish();
        }

        public void StartEditPortfolioActivity(int itemId)
        {
            var intent = EditPortfolioActivity.EditIntent(this, itemId);
            StartActivityForResult(intent, 0);
        }

        public void StartConfigActivity()
        {
            var intent = ConfigActivity.GotoIntent(this);
            StartActivityForResult(intent, 0);
        }

        public void StartViewPortfolioActivity(long portfolioId)
        {
            var intent = PortfolioActivity.ViewIntent(this, portfolioId);
            StartActivityForResult(intent, 0);
        }

        public void StartAddPortfolioActivity()
        {
            var intent = EditPortfolioActivity.AddIntent(this);
            StartActivityForResult(intent, 0);
        }

        #endregion

        private void WireUpEvents()
        {
            AddPortfolioButton.Click += addPortfolioButton_Click;
            PortfolioListView.ItemClick += listView_ItemClick;
            RegisterForContextMenu(PortfolioListView);
        }

        public override void OnCreateContextMenu(IContextMenu menu, View v, IContextMenuContextMenuInfo menuInfo)
        {
            base.OnCreateContextMenu(menu, v, menuInfo);

            var info = (AdapterView.AdapterContextMenuInfo)menuInfo;
            var selectedPortfolioName = ((TextView)info.TargetView).Text.ToS();

            var id = _presenter.GetPortfolioIdForContextMenu(selectedPortfolioName);

            menu.SetHeaderTitle("Options".ToJ());
            menu.Add(0, id, 1, "Rename".ToJ());
            menu.Add(0, id, 2, "Delete".ToJ());
        }

        public override bool OnContextItemSelected(IMenuItem item)
        {
            if (item.TitleFormatted.ToS() == "Rename")
            {
                // Edit
                _presenter.EditPortfolio(item.ItemId);
                return true;
            }
            if (item.TitleFormatted.ToS() == "Delete")
            {
                // Delete
                _presenter.DeletePortfolio(item.ItemId);
                _presenter.RefreshPortfolioList();
                return true;
            }
            return base.OnContextItemSelected(item);
        }

        public override bool OnCreateOptionsMenu(IMenu menu)
        {
            var configItem = menu.Add(0, 1, 1, "Config".ToJ());
            configItem.SetIcon(Android.Resource.Drawable.IcMenuPreferences);
            var exitItem = menu.Add(0, 1, 1, "Exit".ToJ());
            exitItem.SetIcon(Android.Resource.Drawable.IcMenuCloseClearCancel);
            return true;
        }

        public override bool OnOptionsItemSelected(IMenuItem item)
        {
            switch (item.TitleFormatted.ToS())
            {
                case "Config":
                    _presenter.GotoConfig();
                    return true;
                case "Exit":
                    _presenter.ExitApplication();
                    return true;
                default:
                    return base.OnOptionsItemSelected(item);
            }
        }

        private void listView_ItemClick(object sender, ItemEventArgs e)
        {
            _presenter.ViewPortfolio(e.Position);
        }

        private void addPortfolioButton_Click(object sender, EventArgs e)
        {
            _presenter.AddNewPortfolio();
        }

        protected override void OnActivityResult(int requestCode, Result resultCode, Intent data)
        {
            base.OnActivityResult(requestCode, resultCode, data);

            _presenter.RefreshPortfolioList();
        }
    }