QuickPlay/QuickPlay/MainActivity.cs

using System;
using Android.App;
using Android.OS;
using Android.Views;
using Android.Widget;
using Android.Content;
using Android.Support.V7.App;
using Toolbar = Android.Support.V7.Widget.Toolbar;
using GridLayoutManager = Android.Support.V7.Widget.GridLayoutManager;
using Android.Runtime;

namespace QuickPlay
{
    [Activity(Label = "@string/app_name", Theme = "@style/AppTheme", MainLauncher = true)]
    public class MainActivity : AppCompatActivity
    {
        private AppConfiguration appConfig;
        private Android.Support.V7.Widget.RecyclerView recyclerView;
        private IPlayer currentPlayer;

        protected override async void OnCreate(Bundle savedInstanceState)
        {
            base.OnCreate(savedInstanceState);


            // App initialization
            appConfig = AppConfiguration.loadConfiguration();
            var playerConfig = await appConfig.GetPlayerConfig();
            currentPlayer = playerConfig.GetPlayer();

            // UI initialization
            SetContentView(Resource.Layout.activity_main);

            // UI Toolbar initialization
            var toolbar = FindViewById<Toolbar>(Resource.Id.toolbar);
            SetSupportActionBar(toolbar);
            SupportActionBar.Title = "My Toolbar";

            // Hide the play bar by default
            var bar = FindViewById(Resource.Id.currentSongBar);
            bar.Visibility = ViewStates.Invisible;

            // Initialize the RecyclerView
            // Since this is rather complicated, it is in a separate method
            InitializeRecyclerView();

            // I don't know why, but this needs to be here in order to show correct colors and player name.
            OnPlayerUpdate();
        }

        private void InitializeRecyclerView()
        {
            recyclerView = FindViewById<Android.Support.V7.Widget.RecyclerView>(Resource.Id.recyclerView1);
            var layoutStrategy = new LexicographicLayoutStrategy();
            var adapter = new SongRecyclerAdapter(currentPlayer, layoutStrategy);
            adapter.SongClick += OnSongClick;
            recyclerView.SetAdapter(adapter);
            var layoutManager = new GridLayoutManager(this, 2, GridLayoutManager.Vertical, false);
            recyclerView.SetLayoutManager(layoutManager);
        }

        public override bool OnCreateOptionsMenu(IMenu menu)
        {
            MenuInflater.Inflate(Resource.Menu.menu_main, menu);
            return base.OnCreateOptionsMenu(menu);
        }

        public override bool OnOptionsItemSelected(IMenuItem item)
        {
            if (item.ItemId == Resource.Id.action_settings)
            {
                // Set player config URL
                var b = new Android.Support.V7.App.AlertDialog.Builder(this);
                b.SetTitle("Player config URL");
                var input = new EditText(this);
                input.Text = appConfig.playerConfigUrl;
                b.SetView(input);
                b.SetPositiveButton("Set", delegate
                {
                    string text = input.Text;
                    appConfig.playerConfigUrl = text;
                    appConfig.saveConfiguration();
                    Toast.MakeText(this, "Configuration saved, reloading", ToastLength.Short).Show();
                    var i = new Intent(this, typeof(MainActivity));
                    StartActivity(i);
                });
                b.SetNegativeButton("Scan QR", delegate {
                    try
                    {
                        var i = new Intent("com.google.zxing.client.android.SCAN");
                        StartActivityForResult(i, 0);
                    } catch (ActivityNotFoundException) {
                        Toast.MakeText(this, "You need ZXing Barcode scanner for this", ToastLength.Long).Show();
                    }
                });
                b.SetCancelable(true);

                b.Show();
            }

            if (item.ItemId == Resource.Id.action_edit)
            {
                // Hide the play bar
                var bar = FindViewById(Resource.Id.currentSongBar);
                bar.Visibility = ViewStates.Invisible;
            }
            return base.OnOptionsItemSelected(item);
        }
        
        /// <summary>
        /// A callback for all player updates.
        /// 
        /// The update should be easy on resources, so no need to have separate
        /// partial updates. This simply performs full update of the activity
        /// state and views.
        /// </summary>
        public void OnPlayerUpdate()
        {
            TextView playerName = FindViewById<TextView>(Resource.Id.playerNameText);
            playerName.Text = currentPlayer.PlayerName;
            var bar = FindViewById(Resource.Id.currentSongBar);
            switch (currentPlayer.Status)
            {
                case IPlayer.PlayerStatus.Disconnected:
                    Toolbar tb = FindViewById<Toolbar>(Resource.Id.toolbar);
                    tb.SetBackgroundColor(Android.Graphics.Color.Red);
                    bar.Visibility = ViewStates.Invisible;
                    break;
                case IPlayer.PlayerStatus.Playing:
                    ResetToolbarColor();
                    // Show progress bar
                    bar.Visibility = ViewStates.Visible;
                    break;
                case IPlayer.PlayerStatus.Stopped:
                    ResetToolbarColor();
                    bar.Visibility = ViewStates.Invisible;
                    break;
            }
        }
        private void ResetToolbarColor()
        {
            Toolbar tb = FindViewById<Toolbar>(Resource.Id.toolbar);
            tb.SetBackgroundColor(
                new Android.Graphics.Color(
                    Android.Support.V4.Content.ContextCompat.GetColor(this, Resource.Color.colorPrimary)
                    )
                );
        }

        public async void OnSongClick(object sender, IPlayable song)
        {
            await currentPlayer.Play(song);
        } 

        protected new async void OnResume()
        {
            base.OnResume();

            // Reconnect the player
            try
            {
                await currentPlayer.ConnectAsync();
            } catch (CannotConnectException e)
            {
                //TODO: View a toast with details and change some colors?
                var t = Toast.MakeText(this, e.Message + ": " + e.InnerException.Message ?? "", ToastLength.Long);
                t.Show();
            }

            // Refresh player info
            OnPlayerUpdate();
        }
        protected new void OnDestroy()
        {
            base.OnDestroy();

            this.appConfig.saveConfiguration();
        }

        protected override void OnActivityResult(int requestCode, [GeneratedEnum] Result resultCode, Intent data)
        {
            base.OnActivityResult(requestCode, resultCode, data);
            if (requestCode == 0)
            {
                if (resultCode == Result.Ok)
                {
                    string url = data.GetStringExtra("SCAN_RESULT");
                    var cfg = new AppConfiguration { playerConfigUrl = url };
                    cfg.saveConfiguration();
                    Toast.MakeText(this, "Configuration saved, reloading", ToastLength.Short).Show();
                    var i = new Intent(this, typeof(MainActivity));
                    StartActivity(i);
                }
                else if (resultCode == Result.Canceled)
                {
                    Toast.MakeText(this, "Could not load QR code", ToastLength.Short).Show();
                }
            }
        }
    }
}