Merge pull request #1179 from unoplatform/fix/ios.simpleorientation.c…

…rash

fix(iOS): SimpleOrientationSensor Sample Crash

Uno.Gallery/Views/SamplePages/SimpleOrientationSamplePage.xaml.cs

@@ -2,12 +2,17 @@
 using System.ComponentModel;
 using Uno.Gallery.ViewModels;
 using Windows.Devices.Sensors;
+using Windows.ApplicationModel.Core;
+using Windows.UI.Core;
 using Microsoft.UI.Xaml;
 using Microsoft.UI.Xaml.Controls;
 
 namespace Uno.Gallery.Views.Samples
 {
-	[SamplePage(SampleCategory.NonUIFeatures, "Simple Orientation", Description = "This sensor detects the current quadrant orientation of the specified device as well as its face-up or face-down status.", DocumentationLink = "https://learn.microsoft.com/en-us/uwp/api/windows.devices.sensors.simpleorientationsensor")]
+	[SamplePage(
+		SampleCategory.NonUIFeatures,
+		"Simple Orientation", Description = "This sensor detects the current quadrant orientation of the specified device as well as its face-up or face-down status.",
+		DocumentationLink = "https://learn.microsoft.com/en-us/uwp/api/windows.devices.sensors.simpleorientationsensor")]
 	public sealed partial class SimpleOrientationSamplePage : Page
 	{
 		public SimpleOrientationSamplePage()
@@ -17,15 +22,15 @@ public SimpleOrientationSamplePage()
 
 		private void ObserveReadingChangeButton_Click(object sender, RoutedEventArgs e)
 		{
-			if ((sender as Button)?.DataContext is SimpleOrientationSamplePageViewModel viewModel)
+			if (sender is Button { DataContext: SimpleOrientationSamplePageViewModel viewModel })
 			{
-				if (!viewModel.ObservingReadingChange)
+				if (viewModel.ObservingReadingChange)
 				{
-					viewModel.StartObserveReadingChange();
+					viewModel.StopObservingReadingChange();
 				}
 				else
 				{
-					viewModel.StopObservingReadingChange();
+					viewModel.StartObserveReadingChange();
 				}
 			}
 		}
@@ -35,50 +40,60 @@ public class SimpleOrientationSamplePageViewModel : ViewModelBase
 	{
 		private const string _startObservingContent = "Start observing orientation changes";
 		private const string _stopObservingContent = "Stop observing orientation changes";
-		private const string _noSensorAvailable = "SimpleOrientationSensor is not available on this device/platform";
-
-		private readonly SimpleOrientationSensor _simpleOrientationSensor;
+		private const string _noSensorAvailableContent = "SimpleOrientationSensor is not available on this device/platform";
+		private readonly SimpleOrientationSensor? _simpleOrientationSensor;
 
 		public DateTimeOffset? LastReadTimestamp { get => GetProperty<DateTimeOffset?>(); set => SetProperty(value); }
-
 		public string ButtonContent { get => GetProperty<string>(); set => SetProperty(value); }
 		public bool ObservingReadingChange { get => GetProperty<bool>(); set => SetProperty(value); }
 		public SimpleOrientation Orientation { get => GetProperty<SimpleOrientation>(); set => SetProperty(value); }
 
-		public bool SimpleOrientationAvailable => _simpleOrientationSensor != null;
+		public bool SimpleOrientationAvailable => _simpleOrientationSensor is not null;
 
 		public SimpleOrientationSamplePageViewModel()
 		{
 			_simpleOrientationSensor = SimpleOrientationSensor.GetDefault();
 
-			if (_simpleOrientationSensor != null)
+			if (SimpleOrientationAvailable)
 			{
 				ButtonContent = _startObservingContent;
 			}
 			else
 			{
-				ButtonContent = _noSensorAvailable;
+				ButtonContent = _noSensorAvailableContent;
 			}
 		}
 
 		public void StartObserveReadingChange()
 		{
+			if (_simpleOrientationSensor is null)
+			{
+				return;
+			}
+
 			_simpleOrientationSensor.OrientationChanged += SimpleOrientationSensor_OrientationChanged;
 			ButtonContent = _stopObservingContent;
 			ObservingReadingChange = true;
 		}
 
 		public void StopObservingReadingChange()
 		{
-			_simpleOrientationSensor.OrientationChanged -= SimpleOrientationSensor_OrientationChanged;
+			if (_simpleOrientationSensor is not null)
+			{
+				_simpleOrientationSensor.OrientationChanged -= SimpleOrientationSensor_OrientationChanged;
+			}
+
 			ButtonContent = _startObservingContent;
 			ObservingReadingChange = false;
 		}
 
-		private void SimpleOrientationSensor_OrientationChanged(SimpleOrientationSensor sender, SimpleOrientationSensorOrientationChangedEventArgs args)
+		private async void SimpleOrientationSensor_OrientationChanged(SimpleOrientationSensor sender, SimpleOrientationSensorOrientationChangedEventArgs args)
 		{
-			LastReadTimestamp = args.Timestamp;
-			Orientation = args.Orientation;
+			await CoreApplication.MainView.CoreWindow.Dispatcher.RunAsync(CoreDispatcherPriority.Normal, () =>
+			{
+				LastReadTimestamp = args.Timestamp;
+				Orientation = args.Orientation;
+			});
 		}
 	}
 }