ProgressBar Attached Property to enable progress animation (#352)

* ProgressBar Attached Property to enable progress animation

* Fixes remarks on PR

* Fix remarks PR

* Changes need for new gallery viewmodel

* Correct version from before rebase

* Update AttachedPropertiesGalleryViewModel.cs

* Update ProgressBarAttachedProperties.shared.cs

* Update ProgressBarAttachedProperties.shared.cs

* Change Attached property to behavior

* Update samples/XCT.Sample/Xamarin.CommunityToolkit.Sample.csproj

Co-authored-by: Andrei <andrei.misiukevich@gmail.com>

* Update src/CommunityToolkit/Xamarin.CommunityToolkit/Behaviors/ProgressBarAnimationBehavior.cs

Co-authored-by: Andrei <andrei.misiukevich@gmail.com>

* Update src/CommunityToolkit/Xamarin.CommunityToolkit/Xamarin.CommunityToolkit.csproj

Co-authored-by: Andrei <andrei.misiukevich@gmail.com>

* Update src/CommunityToolkit/Xamarin.CommunityToolkit/Behaviors/ProgressBarAnimationBehavior.cs

Co-authored-by: Cfun <15718354+Cfun1@users.noreply.github.com>

* Update src/CommunityToolkit/Xamarin.CommunityToolkit/AttachedProperties/ProgressBarAttachedProperties.shared.cs

Co-authored-by: Cfun <15718354+Cfun1@users.noreply.github.com>

* Remove old attached property and rename new behavior

Co-authored-by: Gerald Versluis <gerald@verslu.is>
Co-authored-by: Andrei <andrei.misiukevich@gmail.com>
Co-authored-by: Cfun <15718354+Cfun1@users.noreply.github.com>

samples/XCT.Sample/Pages/Behaviors/ProgressBarAnimationBehaviorPage.xaml

@@ -0,0 +1,26 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<pages:BasePage xmlns="http://xamarin.com/schemas/2014/forms"
+                xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
+                xmlns:xct="http://xamarin.com/schemas/2020/toolkit"
+                xmlns:pages="clr-namespace:Xamarin.CommunityToolkit.Sample.Pages"
+                xmlns:vm="clr-namespace:Xamarin.CommunityToolkit.Sample.ViewModels.Behaviors"                
+                x:Class="Xamarin.CommunityToolkit.Sample.Pages.Behaviors.ProgressBarAnimationBehaviorPage">
+
+    <pages:BasePage.BindingContext>
+        <vm:ProgressBarAnimationBehaviorViewModel />
+    </pages:BasePage.BindingContext>
+
+    <StackLayout Padding="{StaticResource ContentPadding}"
+                 Spacing="50"
+                 VerticalOptions="CenterAndExpand">
+        <ProgressBar>
+            <ProgressBar.Behaviors>
+                <xct:ProgressBarAnimationBehavior AnimateProgress="{Binding Progress}" />
+            </ProgressBar.Behaviors>
+        </ProgressBar>
+
+        <Button Text="Set to 0" Command="{Binding SetTo0Command}"  />
+        <Button Text="Set to 50" Command="{Binding SetTo50Command}" />
+        <Button Text="Set to 100" Command="{Binding SetTo100Command}" />
+	</StackLayout>
+</pages:BasePage>

samples/XCT.Sample/Pages/Behaviors/ProgressBarAnimationBehaviorPage.xaml.cs

@@ -0,0 +1,10 @@
+using Xamarin.Forms;
+
+namespace Xamarin.CommunityToolkit.Sample.Pages.Behaviors
+{
+	public partial class ProgressBarAnimationBehaviorPage : BasePage
+	{
+		public ProgressBarAnimationBehaviorPage()
+			=> InitializeComponent();
+	}
+}

samples/XCT.Sample/ViewModels/Behaviors/BehaviorsGalleryViewModel.cs

@@ -57,6 +57,10 @@ public class BehaviorsGalleryViewModel : BaseGalleryViewModel
 				typeof(CharactersValidationBehaviorPage),
 				nameof(CharactersValidationBehavior),
 				"Changes an Entry's text color when an invalid string is provided."),
+			new SectionModel(
+				typeof(ProgressBarAnimationBehaviorPage),
+				nameof(ProgressBarAnimationBehavior),
+				"Animate the progress for the ProgressBar")
 		};
 	}
 }

samples/XCT.Sample/ViewModels/Behaviors/ProgressBarAnimationBehaviorViewModel.cs

@@ -0,0 +1,37 @@
+using System;
+using System.Threading.Tasks;
+using System.Windows.Input;
+using Xamarin.CommunityToolkit.ObjectModel;
+
+namespace Xamarin.CommunityToolkit.Sample.ViewModels.Behaviors
+{
+	public class ProgressBarAnimationBehaviorViewModel : BaseViewModel
+	{
+		double progress;
+		ICommand setTo0Command;
+		ICommand setTo50Command;
+		ICommand setTo100Command;
+
+		public double Progress
+		{
+			get => progress;
+			set
+			{
+				progress = value;
+				OnPropertyChanged();
+			}
+		}
+
+		public ICommand SetTo0Command => setTo0Command ??= new AsyncCommand(() => SetProgress(0));
+
+		public ICommand SetTo50Command => setTo50Command ??= new AsyncCommand(() => SetProgress(0.5));
+
+		public ICommand SetTo100Command => setTo100Command ??= new AsyncCommand(() => SetProgress(1));
+
+		async Task SetProgress(double
+			progress)
+		{
+			Progress = progress;
+		}
+	}
+}

samples/XCT.Sample/Xamarin.CommunityToolkit.Sample.csproj

@@ -44,4 +44,3 @@
     <ProjectReference Include="..\..\src\Markup\Xamarin.CommunityToolkit.Markup\Xamarin.CommunityToolkit.Markup.csproj" />
   </ItemGroup>
 </Project>
-

src/CommunityToolkit/Xamarin.CommunityToolkit/Behaviors/ProgressBarAnimationBehavior.shared.cs

@@ -0,0 +1,27 @@
+using System;
+using Xamarin.CommunityToolkit.Behaviors.Internals;
+using Xamarin.Forms;
+
+namespace Xamarin.CommunityToolkit.Behaviors
+{
+	public class ProgressBarAnimationBehavior : BaseBehavior<ProgressBar>
+	{
+		/// <summary>
+		/// Backing BindableProperty for the <see cref="AnimateProgress"/> property.
+		/// </summary>
+		public static readonly BindableProperty AnimateProgressProperty =
+			BindableProperty.CreateAttached(nameof(AnimateProgress), typeof(double), typeof(ProgressBar), 0.0d, propertyChanged: OnAnimateProgressPropertyChanged);
+
+		public double AnimateProgress
+		{
+			get => (double)GetValue(AnimateProgressProperty);
+			set => SetValue(AnimateProgressProperty, value);
+		}
+
+		static void OnAnimateProgressPropertyChanged(BindableObject bindable, object oldValue, object newValue)
+			=> ((ProgressBarAnimationBehavior)bindable).Animate();
+
+		void Animate()
+			=> View.ProgressTo(AnimateProgress, 500, Easing.Linear);
+	}
+}