Add a menu for changing themes

Tasks/Lab12/TodoDetails/AppShell.xaml

@@ -4,12 +4,12 @@
     xmlns="http://schemas.microsoft.com/dotnet/2021/maui"
     xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
     xmlns:local="clr-namespace:TodoDetails"
-    Shell.FlyoutBehavior="Disabled"
+    xmlns:view="clr-namespace:TodoDetails.View"
-    Title="TodoDetails">
+    Shell.FlyoutBehavior="Flyout">
-
+    <ShellContent Title="Home"
-    <ShellContent
-        Title="Home"
                   ContentTemplate="{DataTemplate local:MainPage}"
                   Route="MainPage" />
-
+    <ShellContent Title="Settings"
+                  ContentTemplate="{DataTemplate view:SettingsPage}"
+                  Route="SettingsPage"/>
 </Shell>

Tasks/Lab12/TodoDetails/MauiProgram.cs

@@ -24,6 +24,8 @@ namespace TodoDetails
             builder.Services.AddSingleton<TodoService>();
             builder.Services.AddSingleton<TodosViewModel>();
             builder.Services.AddSingleton<MainPage>();
+            builder.Services.AddSingleton<SettingsViewModel>();
+            builder.Services.AddSingleton<SettingsPage>();
             builder.Services.AddTransient<TodoDetailsViewModel>();
             builder.Services.AddTransient<TodoDetailsPage>();
 

Tasks/Lab12/TodoDetails/Resources/Styles/ThemeStyles.xaml

@@ -0,0 +1,6 @@
+<?xml version="1.0" encoding="utf-8" ?>
+<ResourceDictionary xmlns="http://schemas.microsoft.com/dotnet/2021/maui"
+             xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
+             x:Class="TodoDetails.Resources.Styles.ThemeStyles">
+
+</ResourceDictionary>

Tasks/Lab12/TodoDetails/Resources/Styles/ThemeStyles.xaml.cs

@@ -0,0 +1,9 @@
+namespace TodoDetails.Resources.Styles;
+
+public partial class ThemeStyles : ResourceDictionary
+{
+	public ThemeStyles()
+	{
+		InitializeComponent();
+	}
+}

Tasks/Lab12/TodoDetails/Resources/Themes/BasicTheme.xaml

@@ -0,0 +1,6 @@
+<?xml version="1.0" encoding="utf-8" ?>
+<ResourceDictionary xmlns="http://schemas.microsoft.com/dotnet/2021/maui"
+             xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
+             x:Class="TodoDetails.Resources.Themes.BasicTheme">
+
+</ResourceDictionary>

Tasks/Lab12/TodoDetails/Resources/Themes/BasicTheme.xaml.cs

@@ -0,0 +1,9 @@
+namespace TodoDetails.Resources.Themes;
+
+public partial class BasicTheme : ResourceDictionary
+{
+	public BasicTheme()
+	{
+		InitializeComponent();
+	}
+}

Tasks/Lab12/TodoDetails/Resources/Themes/Dark.xaml

@@ -0,0 +1,6 @@
+<?xml version="1.0" encoding="utf-8" ?>
+<ResourceDictionary xmlns="http://schemas.microsoft.com/dotnet/2021/maui"
+             xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
+             x:Class="TodoDetails.Resources.Themes.Dark">
+
+</ResourceDictionary>

Tasks/Lab12/TodoDetails/Resources/Themes/Dark.xaml.cs

@@ -0,0 +1,9 @@
+namespace TodoDetails.Resources.Themes;
+
+public partial class Dark : ResourceDictionary
+{
+	public Dark()
+	{
+		InitializeComponent();
+	}
+}

Tasks/Lab12/TodoDetails/Resources/Themes/Earth.xaml

@@ -0,0 +1,6 @@
+<?xml version="1.0" encoding="utf-8" ?>
+<ResourceDictionary xmlns="http://schemas.microsoft.com/dotnet/2021/maui"
+             xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
+             x:Class="TodoDetails.Resources.Themes.Earth">
+
+</ResourceDictionary>

Tasks/Lab12/TodoDetails/Resources/Themes/Earth.xaml.cs

@@ -0,0 +1,9 @@
+namespace TodoDetails.Resources.Themes;
+
+public partial class Earth : ResourceDictionary
+{
+	public Earth()
+	{
+		InitializeComponent();
+	}
+}

Tasks/Lab12/TodoDetails/Resources/Themes/Light.xaml

@@ -0,0 +1,6 @@
+<?xml version="1.0" encoding="utf-8" ?>
+<ResourceDictionary xmlns="http://schemas.microsoft.com/dotnet/2021/maui"
+             xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
+             x:Class="TodoDetails.Resources.Themes.Light">
+
+</ResourceDictionary>

Tasks/Lab12/TodoDetails/Resources/Themes/Light.xaml.cs

@@ -0,0 +1,9 @@
+namespace TodoDetails.Resources.Themes;
+
+public partial class Light : ResourceDictionary
+{
+	public Light()
+	{
+		InitializeComponent();
+	}
+}

Tasks/Lab12/TodoDetails/Resources/Themes/Pink.xaml

@@ -0,0 +1,6 @@
+<?xml version="1.0" encoding="utf-8" ?>
+<ResourceDictionary xmlns="http://schemas.microsoft.com/dotnet/2021/maui"
+             xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
+             x:Class="TodoDetails.Resources.Themes.Pink">
+
+</ResourceDictionary>

Tasks/Lab12/TodoDetails/Resources/Themes/Pink.xaml.cs

@@ -0,0 +1,9 @@
+namespace TodoDetails.Resources.Themes;
+
+public partial class Pink : ResourceDictionary
+{
+	public Pink()
+	{
+		InitializeComponent();
+	}
+}

Tasks/Lab12/TodoDetails/TodoDetails.csproj

@@ -68,6 +68,27 @@
 	</ItemGroup>
 
 	<ItemGroup>
+	  <MauiXaml Update="Resources\Styles\ThemeStyles.xaml">
+	    <Generator>MSBuild:Compile</Generator>
+	  </MauiXaml>
+	  <MauiXaml Update="Resources\Themes\BasicTheme.xaml">
+	    <Generator>MSBuild:Compile</Generator>
+	  </MauiXaml>
+	  <MauiXaml Update="Resources\Themes\Dark.xaml">
+	    <Generator>MSBuild:Compile</Generator>
+	  </MauiXaml>
+	  <MauiXaml Update="Resources\Themes\Earth.xaml">
+	    <Generator>MSBuild:Compile</Generator>
+	  </MauiXaml>
+	  <MauiXaml Update="Resources\Themes\Light.xaml">
+	    <Generator>MSBuild:Compile</Generator>
+	  </MauiXaml>
+	  <MauiXaml Update="Resources\Themes\Pink.xaml">
+	    <Generator>MSBuild:Compile</Generator>
+	  </MauiXaml>
+	  <MauiXaml Update="View\SettingsPage.xaml">
+	    <Generator>MSBuild:Compile</Generator>
+	  </MauiXaml>
 	  <MauiXaml Update="View\TodoDetailsPage.xaml">
 	    <Generator>MSBuild:Compile</Generator>
 	  </MauiXaml>

Tasks/Lab12/TodoDetails/View/SettingsPage.xaml

@@ -0,0 +1,16 @@
+<?xml version="1.0" encoding="utf-8" ?>
+<ContentPage xmlns="http://schemas.microsoft.com/dotnet/2021/maui"
+             xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
+             xmlns:viewmodel="clr-namespace:TodoDetails.ViewModel"
+             x:Class="TodoDetails.View.SettingsPage"
+             x:DataType="viewmodel:SettingsViewModel"
+             Title="SettingsPage">
+    <Border>
+        <VerticalStackLayout Padding="5">
+            <Picker x:Name="ThemePicker"
+                    Title="Pick a Theme"
+                    SelectedIndexChanged="SelectedThemeChanged"
+                    ItemsSource="{Binding Themes}"/>
+        </VerticalStackLayout>
+    </Border>
+</ContentPage>

Tasks/Lab12/TodoDetails/View/SettingsPage.xaml.cs

@@ -0,0 +1,22 @@
+using TodoDetails.ViewModel;
+
+namespace TodoDetails.View;
+
+public partial class SettingsPage : ContentPage
+{
+	public SettingsPage(SettingsViewModel viewModel)
+	{
+		InitializeComponent();
+		BindingContext = viewModel;
+	}
+
+    private void SelectedThemeChanged(object sender, EventArgs e)
+    {
+		var selectedItem = (string)ThemePicker.SelectedItem;
+
+		if (selectedItem != null)
+		{
+			(BindingContext as SettingsViewModel)?.LoadNewTheme(selectedItem);
+		}
+    }
+}

Tasks/Lab12/TodoDetails/ViewModel/SettingsViewModel.cs

@@ -0,0 +1,46 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+using TodoDetails.Resources.Styles;
+using TodoDetails.Resources.Themes;
+
+namespace TodoDetails.ViewModel
+{
+    public class SettingsViewModel
+    {
+        private Dictionary<string, ResourceDictionary> defaultThemes = new()
+        {
+            { "Light", new Light() },
+            { "Dark", new Dark() },
+            { "Earth", new Earth() },
+            { "Pink", new Pink() }
+        };
+
+        public SettingsViewModel()
+        {
+            Themes = defaultThemes.Select(x => x.Key).ToList();
+        }
+
+        public List<string> Themes { get; set; }
+
+        public void LoadNewTheme(string themeName)
+        {
+            if (!MainThread.IsMainThread)
+            {
+                MainThread.BeginInvokeOnMainThread(() => LoadNewTheme(themeName));
+                return;
+            }
+
+            ResourceDictionary dictionary = defaultThemes[themeName];
+
+            if (dictionary != null)
+            {
+                Application.Current.Resources.MergedDictionaries.Clear();
+                Application.Current.Resources.MergedDictionaries.Add(new ThemeStyles());
+                Application.Current.Resources.MergedDictionaries.Add(dictionary);
+            }
+        }
+    }
+}