MainPage.xaml.cs

using System;
using System.Collections.Generic;
using System.Collections.ObjectModel;
using System.Diagnostics;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using WunderlistApp.Model;
using Xamarin.Forms;
using Xamarin.Forms.Xaml;

namespace WunderlistApp.View
{
    [XamlCompilation(XamlCompilationOptions.Compile)]
    public partial class MainPage : TabbedPage
    {
        ObservableCollection<Folder> ObservedFoldersList;
        ObservableCollection<Lists> ObservedListsList;

        public MainPage()
        {
            GeneratePage();
            InitializeComponent();

            // Set different colors :D
            this.BarBackgroundColor = Color.FromHex("#5b7a59");
            this.BarTextColor = Color.FromHex("#ffffff");
            this.BackgroundColor = Color.FromHex("#f7f7f7");
        }


        private async Task GeneratePage()
        {
            List<Folder> folders = await ApiManager.GetFoldersAsync();
            ObservedFoldersList = new ObservableCollection<Folder>(folders);

            // TEMPLATE
            // Make a template for the view
            var template = new DataTemplate(typeof(TextCell));
            // Create a text-field (same as <Label /> in xaml).
            // title is here the property of the class Lists
            template.SetBinding(TextCell.TextProperty, "title");
            // Set a color to the label.
            template.SetValue(TextCell.TextColorProperty, Color.FromHex("#212121"));


            // Make the splashscreen
            ActivityIndicator actInd = new ActivityIndicator
            {
                IsRunning = true,
                IsEnabled = true,
                VerticalOptions = LayoutOptions.Center
            };

            ContentPage loadingPage = new ContentPage
            {
                Content = new Grid
                {
                    Children =
                        {
                            actInd
                        }
                }
            };

            // Generate the page
            this.Children.Add(loadingPage);


            // Loop trough the folders with var f
            foreach (var f in ObservedFoldersList)
            {
                // Make a new List object for the lists in a folder
                List<Lists> lists = new List<Lists>();
                ObservedListsList = new ObservableCollection<Lists>(lists);
                // Loop trough the ID's of the lists
                foreach (int id in f.list_ids)
                {
                    // Add the lists to the lists object using an async link.
                    ObservedListsList.Add(await ApiManager.GetSpecificListAsync(id));
                }

                // listview for the ContentPage
                ListView lvwLists = new ListView
                {
                    ItemsSource = ObservedListsList,
                    SeparatorVisibility = SeparatorVisibility.None,
                    // Here, we specify the template to be used (it's defined above of this) under the 'TEMPLATE' tag.
                    ItemTemplate = template
                };

                Button btn_add_new_list = new Button
                {
                    Text = "Add a new list",
                    BackgroundColor = Color.FromHex("#5b7a59"),
                    TextColor = Color.FromHex("#FAFAFA"),
                    BorderRadius = 0,
                    Margin = new Thickness(20),
                    CommandParameter = f
                };

                // Event listeners
                lvwLists.ItemSelected += LvwLists_ItemSelected;
                btn_add_new_list.Clicked += Btn_add_new_list_Clicked;

                ContentPage page = new ContentPage
                {
                    Title = f.title,
                    Content = new StackLayout
                    {
                        Children =
                        {
                            lvwLists,
                            btn_add_new_list
                        }
                    }
                };

                // Generate the page
                this.Children.Add(page);
            }
            this.Children.Remove(loadingPage);
            actInd.IsRunning = false;
        }

        // Selected event, this will pass the data to the new page and there we can select the data to make a detail :)
        private void LvwLists_ItemSelected(object sender, SelectedItemChangedEventArgs e)
        {
            ListView lv = sender as ListView;

            //Lists selected = lvwLists.SelectedItem as Lists;
            Lists selected = lv.SelectedItem as Lists;
            if (selected != null)
            {
                // DisplayAlert("ID item Selected: ", selected.id.ToString(), "Ok");
                Navigation.PushAsync(new DetailListPage(selected.id, selected.title));
                
                // disable the visual selection state
                ((ListView)sender).SelectedItem = null;
            }
        }

        private void Btn_add_new_list_Clicked(object sender, EventArgs e)
        {
            // DisplayAlert("Whoops!", "Ahw, something went wrong! Can't make a new item, because the API screwed up...", "Ok");
            
            Folder selected_folder = (sender as Button).CommandParameter as Folder;

            Debug.WriteLine(selected_folder);

            Navigation.PushAsync(new AddListPage(selected_folder));
            
        }
    }
}