Implement a ToDo overview based on a JSON file

Tasks/Lab12/TodoDetails/MainPage.xaml

@@ -2,46 +2,62 @@
 <ContentPage xmlns="http://schemas.microsoft.com/dotnet/2021/maui"
              xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
              xmlns:model="clr-namespace:TodoDetails.Model"
-             x:Class="TodoDetails.MainPage">
+             xmlns:viewmodel="clr-namespace:TodoDetails.ViewModel"
-
+             x:DataType="viewmodel:TodosViewModel"
-    <ScrollView>
+             x:Class="TodoDetails.MainPage"
-        <CollectionView>
+             Title="{Binding Title}">
-            <CollectionView.ItemsSource>
+    <Grid ColumnSpacing="5"
-                <x:Array Type="{x:Type model:Todo}">
+          RowSpacing="0">
-                    <model:Todo Title="Create ViewModel"
+        <Grid.ColumnDefinitions>
-                                Description="Create a ViewModel in the next step to learn MVVM."
+            <ColumnDefinition/>
-                                Category="Default"
+            <ColumnDefinition/>
-                                IsDone="False"/>
+        </Grid.ColumnDefinitions>
-                    <model:Todo Title="Add Theming"
+        <Grid.RowDefinitions>
-                                Description="Integrate your own theme in the app."
+            <RowDefinition/>
-                                Category="Default"
+            <RowDefinition Height="Auto"/>
-                                IsDone="False"/>
+        </Grid.RowDefinitions>
-                    <model:Todo Title="Add local database"
+        <CollectionView ItemsSource="{Binding Todos}"
-                                Description="Learn how to add a local database to work with (optional)."
+                        SelectionMode="None"
-                                Category="Default"
+                        Grid.ColumnSpan="2">
-                                IsDone="False"/>
-                </x:Array>
-            </CollectionView.ItemsSource>
             <CollectionView.ItemTemplate>
                 <DataTemplate x:DataType="model:Todo">
-                    <HorizontalStackLayout Padding="10"
+                    <Grid Padding="10">
-                                           Spacing="10"
+                        <Border HeightRequest="125">
-                                           HorizontalOptions="FillAndExpand">
+                            <Grid Padding="0">
-                        <CheckBox IsChecked="{Binding IsDone}"
+                                <Grid.ColumnDefinitions>
-                                  VerticalOptions="Start"/>
+                                    <ColumnDefinition/>
-                        <VerticalStackLayout VerticalOptions="Center">
+                                    <ColumnDefinition/>
-                            <Label Text="{Binding Title}"
+                                    <ColumnDefinition/>
+                                </Grid.ColumnDefinitions>
+                                <CheckBox IsChecked="{Binding IsDone}"/>
+                                <VerticalStackLayout Grid.Column="1"
                                                      VerticalOptions="Center"
-                                   FontSize="16"
+                                                     Padding="10">
-                                   TextColor="Gray"/>
+                                    <Label Text="{Binding Title}"
+                                           FontSize="16"/>
                                     <Label Text="{Binding Category}"
-                                   FontSize="12"
+                                           FontSize="12"/>
-                                   TextColor="Gray"/>
                                 </VerticalStackLayout>
-                    </HorizontalStackLayout>
+                                <Label Text="{Binding DueDate}"
+                                       Grid.Column="2"
+                                       VerticalOptions="Center"/>
+                            </Grid>
+                        </Border>
+                    </Grid>
                 </DataTemplate>
             </CollectionView.ItemTemplate>
         </CollectionView>
-    </ScrollView>
+        <Button Text="Fetch Todos"
-
+                Command="{Binding GetTodosCommand}"
+                IsEnabled="{Binding IsNotBusy}"
+                Grid.Row="1"
+                Margin="8"/>
+        <ActivityIndicator IsVisible="{Binding IsBusy}"
+                           IsRunning="{Binding IsBusy}"
+                           HorizontalOptions="Fill"
+                           VerticalOptions="Center"
+                           Color="{DynamicResource Primary}"
+                           Grid.RowSpan="2"
+                           Grid.ColumnSpan="2"/>
+    </Grid>
 </ContentPage>

Tasks/Lab12/TodoDetails/MainPage.xaml.cs

@@ -1,12 +1,13 @@
+using TodoDetails.ViewModel;
+
 namespace TodoDetails
 {
     public partial class MainPage : ContentPage
     {
-        int count = 0;
+        public MainPage(TodosViewModel viewModel)
-
-        public MainPage()
         {
             InitializeComponent();
+            BindingContext = viewModel;
         }
     }
 

Tasks/Lab12/TodoDetails/MauiProgram.cs

@@ -1,4 +1,6 @@
 using Microsoft.Extensions.Logging;
+using TodoDetails.Services;
+using TodoDetails.ViewModel;
 
 namespace TodoDetails
 {
@@ -18,6 +20,9 @@ namespace TodoDetails
 #if DEBUG
     		builder.Logging.AddDebug();
 #endif
+            builder.Services.AddSingleton<TodoService>();
+            builder.Services.AddSingleton<TodosViewModel>();
+            builder.Services.AddSingleton<MainPage>();
 
             return builder.Build();
         }

Tasks/Lab12/TodoDetails/Resources/Raw/tododata.json

@@ -0,0 +1,23 @@
+[
+  {
+    "Title": "Create ViewModel",
+    "Description": "Create a ViewModel in the next step to learn MVVM.",
+    "IsDone": true,
+    "Category": "Default",
+    "DueDate": "2023-05-31T00:00:00"
+  },
+  {
+    "Title": "Add Themeing",
+    "Description": "Integrate your own theme in the app.",
+    "IsDone": false,
+    "Category": "Default",
+    "DueDate": "2023-05-31T00:00:00"
+  },
+  {
+    "Title": "Add local database",
+    "Description": "Learn how to add a local database.",
+    "IsDone": false,
+    "Category": "Default",
+    "DueDate": "2023-05-31T00:00:00"
+  }
+]

Tasks/Lab12/TodoDetails/Services/TodoService.cs

@@ -0,0 +1,40 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using System.Text.Json;
+using System.Threading.Tasks;
+using TodoDetails.Model;
+
+namespace TodoDetails.Services
+{
+    public class TodoService
+    {
+        Lazy<Task<List<Todo>>> todoList;
+
+        public TodoService()
+        {
+            todoList = new Lazy<Task<List<Todo>>>(
+                async () =>
+                {
+                    List<Todo>? result = null;
+
+                    using var stream = await FileSystem.OpenAppPackageFileAsync("tododata.json");
+                    using var reader = new StreamReader(stream);
+                    var contents = await reader.ReadToEndAsync();
+
+                    if (contents != null)
+                    {
+                        result = JsonSerializer.Deserialize<List<Todo>>(contents);
+                    }
+
+                    return result ?? new();
+                });
+        }
+
+        public async Task<List<Todo>> GetTodos()
+        {
+            return await todoList.Value;
+        }
+    }
+}

Tasks/Lab12/TodoDetails/TodoDetails.csproj

@@ -57,6 +57,11 @@
 	</ItemGroup>
 
 	<ItemGroup>
+	  <None Remove="Resources\raw\tododata.json" />
+	</ItemGroup>
+
+	<ItemGroup>
+		<PackageReference Include="CommunityToolkit.Mvvm" Version="8.2.2" />
 		<PackageReference Include="Microsoft.Maui.Controls" Version="$(MauiVersion)" />
 		<PackageReference Include="Microsoft.Maui.Controls.Compatibility" Version="$(MauiVersion)" />
 		<PackageReference Include="Microsoft.Extensions.Logging.Debug" Version="8.0.0" />

Tasks/Lab12/TodoDetails/ViewModel/BaseViewModel.cs

@@ -0,0 +1,21 @@
+using CommunityToolkit.Mvvm.ComponentModel;
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+
+namespace TodoDetails.ViewModel
+{
+    public partial class BaseViewModel : ObservableObject
+    {
+        [ObservableProperty]
+        [NotifyPropertyChangedFor(nameof(IsNotBusy))]
+        bool isBusy;
+
+        [ObservableProperty]
+        string? title;
+
+        public bool IsNotBusy => !IsBusy;
+    }
+}

Tasks/Lab12/TodoDetails/ViewModel/TodosViewModel.cs

@@ -0,0 +1,68 @@
+using CommunityToolkit.Mvvm.Input;
+using System;
+using System.Collections.Generic;
+using System.Collections.ObjectModel;
+using System.Diagnostics;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+using TodoDetails.Model;
+using TodoDetails.Services;
+
+namespace TodoDetails.ViewModel
+{
+    public partial class TodosViewModel : BaseViewModel
+    {
+        public ObservableCollection<Todo> Todos { get; } = new ObservableCollection<Todo>();
+        TodoService todoService;
+
+        public TodosViewModel(TodoService todoService)
+        {
+            Title = "Todos";
+            this.todoService = todoService;
+        }
+
+        [RelayCommand]
+        async Task GetTodosAsync()
+        {
+            if (IsBusy)
+            {
+                return;
+            }
+
+            try
+            {
+                IsBusy = true;
+                var todos = await todoService.GetTodos();
+
+                if (Todos.Count != 0)
+                {
+                    Todos.Clear();
+                }
+
+                foreach (var todo in todos)
+                {
+                    Todos.Add(todo);
+                }
+            }
+            catch (Exception e)
+            {
+                Debug.WriteLine($"UInable to get todos: {e.Message}");
+                await Shell.Current.DisplayAlert("Error!", e.Message, "OK");
+            }
+            finally
+            {
+                IsBusy = false;
+            }
+        }
+
+        [RelayCommand]
+        async Task GoToDetails(Todo todo)
+        {
+            if (todo == null)
+            {
+                return;
+            }
+        }
+    }
+}