15 - NotiXamarin - Seleccion Multiple

// NewsListRow.axml

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:id="@+id/newsListRow_RelativeLayout"
    android:background="@color/listitemunselected">
    <TextView
        android:text="Small Text"
        android:textAppearance="?android:attr/textAppearanceSmall"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_toLeftOf="@id/newsImage"
        android:layout_alignParentLeft="true"
        android:textStyle="bold"
        android:layout_marginLeft="5dp"
        android:layout_marginTop="5dp"
        android:id="@+id/newsTitle" />
    <ImageView
        android:src="@android:drawable/ic_menu_gallery"
        android:layout_width="100dp"
        android:layout_height="100dp"
        android:layout_alignParentRight="true"
        android:layout_alignParentTop="true"
        android:layout_marginLeft="15dp"
        android:layout_marginRight="15dp"
        android:id="@+id/newsImage" />
</RelativeLayout>

// Colors.xml

<?xml version="1.0" encoding="utf-8"?>
<resources>
    <color name="listitemselected">#78909c</color>
    <color name="listitemunselected">#303030</color>
</resources>

// ISelectedChecker

internal interface ISelectedChecker
    {
        bool IsItemSelected(int id);
    }

// BasesNewsListFragment.cs

 public class BaseNewsListFragment : Fragment, ISelectedChecker
    {
        protected ListView _newsListView;
        protected List<News> _news;
        protected List<News> _selectedNews;
        private NewsListAdapter _newsListAdapter;

        public BaseNewsListFragment()
        {
            _news = new List<News>();
            _selectedNews = new List<News>();
        }

        public override void OnCreate(Bundle savedInstanceState)
        {
            _selectedNews.Clear();
            base.OnCreate(savedInstanceState);
            SetHasOptionsMenu(true);
        }

        protected void SetupFragment()
        {
            SetupViews();

            SetupEvents();

            SetupAdapter();
        }

        protected void SetupAdapter()
        {
            _newsListAdapter = new NewsListAdapter(Activity, _news, this);
            _newsListView.Adapter = _newsListAdapter;
        }

        protected void SetupViews()
        {
            _newsListView = View.FindViewById<ListView>(Resource.Id.newsListView);
        }

        protected void SetupEvents()
        {
            _newsListView.ItemClick += NewsListView_ItemClick;
            _newsListView.ItemLongClick += _newsListView_ItemLongClick;
        }

        private void _newsListView_ItemLongClick(object sender, AdapterView.ItemLongClickEventArgs e)
        {
            int id = (int)e.Id;
            View view = e.View;

            RelativeLayout rl = view.FindViewById<RelativeLayout>(Resource.Id.newsListRow_RelativeLayout);

            if (_selectedNews.Select(x => x.Id).Contains(id))
            {
                // deselect element
                var colorForUnselected = Resources.GetString(Resource.Color.listitemunselected);
                rl.SetBackgroundColor(Android.Graphics.Color.ParseColor(colorForUnselected));
                _selectedNews.Remove(_newsListAdapter[e.Position]);
            }
            else
            {
                // select element
                var colorForSelected = Resources.GetString(Resource.Color.listitemselected);
                rl.SetBackgroundColor(Android.Graphics.Color.ParseColor(colorForSelected));
                _selectedNews.Add(_newsListAdapter[e.Position]);
            }

            // Forces android to execute OnCreateOptionsMenu
            Activity.InvalidateOptionsMenu();
        }

        private void NewsListView_ItemClick(object sender, AdapterView.ItemClickEventArgs e)
        {
            var intent = new Intent(Activity, typeof(MainActivity));
            var id = (int)e.Id;
            intent.PutExtra(MainActivity.KEY_ID, id);
            StartActivity(intent);
        }

        public override View OnCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState)
        {
            return inflater.Inflate(Resource.Layout.NewsListFragment, container, false);
        }

        protected void UnselectElements()
        {
            int count = _newsListView.ChildCount;

            for (int i = 0; i < count; i++)
            {
                View row = _newsListView.GetChildAt(i);
                var rl = row.FindViewById<RelativeLayout>(Resource.Id.newsListRow_RelativeLayout);
                var color = Resources.GetString(Resource.Color.listitemunselected);
                rl.SetBackgroundColor(Android.Graphics.Color.ParseColor(color));
            }
        }

        public bool IsItemSelected(int id)
        {
            return _selectedNews.Select(x => x.Id).Contains(id);
        }
    }

// AllNewsListFragment

public class AllNewsListFragment : BaseNewsListFragment
    {
        private NewsService _newsService;

        public AllNewsListFragment()
        {
            _newsService = new NewsService();
        }

        public override void OnActivityCreated(Bundle savedInstanceState)
        {
            base.OnActivityCreated(savedInstanceState);

            if (!_news.Any())
            {
                _news = _newsService.GetNews();
            }

            SetupFragment();
        }

        public override void OnCreateOptionsMenu(IMenu menu, MenuInflater inflater)
        {
            if (_selectedNews.Count > 0)
            {
                inflater.Inflate(Resource.Menu.newsActionMenu, menu);
            }

            base.OnCreateOptionsMenu(menu, inflater);
        }

        public override bool OnOptionsItemSelected(IMenuItem item)
        {
            switch (item.ItemId)
            {
                case Resource.Id.action_read_later:
                    SaveSelectedNews(_selectedNews);
                    return true;
                default:
                    return base.OnOptionsItemSelected(item);
            }
        }

        private void SaveSelectedNews(List<News> selectedNews)
        {
            try
            {
                var newsLocalService = new NewsLocalService();
                foreach (var news in selectedNews)
                {
                    newsLocalService.Save(news);
                }

                Toast.MakeText(Activity, $"{selectedNews.Count} news saved", ToastLength.Short).Show();
                selectedNews.Clear();
                Activity.InvalidateOptionsMenu();
                UnselectElements();
            }
            catch (Exception ex)
            {
                Toast.MakeText(Activity, ex.Message, ToastLength.Short).Show();
            }
        }
    }

// SavedNewsListFragment

public class SavedNewsListFragment : BaseNewsListFragment
    {
        private NewsLocalService _newsLocalService;

        public SavedNewsListFragment()
        {
            _newsLocalService = new NewsLocalService();
        }

        public override void OnActivityCreated(Bundle savedInstanceState)
        {
            base.OnActivityCreated(savedInstanceState);

            FillNews();

            SetupFragment();
        }

        private void FillNews()
        {
            _news = _newsLocalService.GetAllSavedForReadLater();
        }

        public override void OnCreateOptionsMenu(IMenu menu, MenuInflater inflater)
        {
            if (_selectedNews.Count > 0)
            {
                inflater.Inflate(Resource.Menu.savedNewsActionMenu, menu);
            }

            base.OnCreateOptionsMenu(menu, inflater);
        }

        public override bool OnOptionsItemSelected(IMenuItem item)
        {
            switch (item.ItemId)
            {
                case Resource.Id.delete_saved_news:
                    DeleteSelectedNews(_selectedNews);
                    return true;
                default:
                    return base.OnOptionsItemSelected(item);
            }
        }

        private void DeleteSelectedNews(List<News> selectedNews)
        {
            try
            {
                foreach (var news in selectedNews)
                {
                    _newsLocalService.Delete(news.Id);
                }

                Toast.MakeText(Activity, $"{selectedNews.Count} news deleted", ToastLength.Short).Show();

                selectedNews.Clear();
                FillNews();
                SetupAdapter();
                Activity.InvalidateOptionsMenu();
            }
            catch (Exception ex)
            {
                Toast.MakeText(Activity, ex.Message, ToastLength.Long).Show();
            }
        }
    }

// NewsListAdapter

  class NewsListAdapter : BaseAdapter<News>
    {
        private Activity _context;
        private List<News> _news;
        private ISelectedChecker _selectedChecker;

        public NewsListAdapter(Activity context, List<News> news, ISelectedChecker selectedChecker)
        {
            _context = context;
            _news = news;
            _selectedChecker = selectedChecker;
        }


        public override News this[int position] => _news[position];

        public override int Count => _news.Count;

        public override long GetItemId(int position)
        {
            return this[position].Id;
        }

        public override View GetView(int position, View convertView, ViewGroup parent)
        {
            var item = this[position];

            if (convertView == null)
            {
                convertView = _context.LayoutInflater.Inflate(Resource.Layout.NewsListRow, null);
            }
            else
            {
                var id = (int)GetItemId(position);
                RelativeLayout rl = convertView.FindViewById<RelativeLayout>(Resource.Id.newsListRow_RelativeLayout);

                if (_selectedChecker.IsItemSelected(id))
                {
                    var colorForSelected = _context.Resources.GetString(Resource.Color.listitemselected);
                    rl.SetBackgroundColor(Android.Graphics.Color.ParseColor(colorForSelected));
                }
                else
                {
                    var colorForUnselected = _context.Resources.GetString(Resource.Color.listitemunselected);
                    rl.SetBackgroundColor(Android.Graphics.Color.ParseColor(colorForUnselected));
                }
            }

            convertView.FindViewById<TextView>(Resource.Id.newsTitle).Text = item.Title;
            var newsImage = convertView.FindViewById<ImageView>(Resource.Id.newsImage);

            var imageURL = string.Concat(ValuesService.ImagesBaseURL, item.ImageName);

            Picasso.With(_context)
                .Load(imageURL)
                .Placeholder(_context.GetDrawable(Resource.Drawable.Icon))
                .Into(newsImage);

            return convertView;
        }
    }

// savedNewsActionMenu

<?xml version="1.0" encoding="utf-8" ?>
<!--For all properties see: http://developer.android.com/guide/topics/resources/menu-resource.html-->
<menu xmlns:android="http://schemas.android.com/apk/res/android">

  <item android:id="@+id/delete_saved_news"
         android:showAsAction="always"
         android:icon="@android:drawable/ic_delete" />

</menu>