fix(iOS): add start/stop MotionManager events

src/Uno.UWP/Devices/Sensors/SimpleOrientationSensor.cs

@@ -32,6 +32,9 @@ public static SimpleOrientationSensor GetDefault()
 
 		private static partial SimpleOrientationSensor TryCreateInstance();
 
+		partial void StartListeningOrientationChanged();
+
+		partial void StopListeningOrientationChanged();
 
 		#endregion
 

src/Uno.UWP/Devices/Sensors/SimpleOrientationSensor.iOS.cs

@@ -22,6 +22,43 @@ public partial class SimpleOrientationSensor
 				: null;
 		}
 
+		partial void StartListeningOrientationChanged()
+		{
+			_motionManager ??= new();
+
+			if (!_motionManager.DeviceMotionAvailable)
+			{
+				if (this.Log().IsEnabled(LogLevel.Error))
+				{
+					this.Log().Error("SimpleOrientationSensor failed to Start. CoreMotion is not available");
+				}
+			}
+
+			if (this.Log().IsEnabled(LogLevel.Information))
+			{
+				this.Log().Info("DeviceMotion is available");
+			}
+
+			var operationQueue = (NSOperationQueue.CurrentQueue == null || NSOperationQueue.CurrentQueue == NSOperationQueue.MainQueue)
+				? new NSOperationQueue()
+				: NSOperationQueue.CurrentQueue;
+
+			_motionManager.DeviceMotionUpdateInterval = _updateInterval;
+
+			_motionManager.StartDeviceMotionUpdates(operationQueue, OnMotionChanged);
+		}
+
+		partial void StopListeningOrientationChanged()
+		{
+			if (_motionManager is null)
+			{
+				return;
+			}
+
+			_motionManager.StopDeviceMotionUpdates();
+			_motionManager.Dispose();
+			_motionManager = null;
+		}
 
 		partial void Initialize()
 		{
@@ -66,7 +103,7 @@ partial void Initialize()
 						return;
 					}
 
-					OnMotionChanged(motion);
+					OnMotionChanged(motion, error);
 				});
 			}
 			else // For iOS devices that don't support CoreMotion
@@ -78,9 +115,31 @@ partial void Initialize()
 			}
 		}
 
-		private void OnMotionChanged(CMDeviceMotion motion)
+		private void OnMotionChanged(CMDeviceMotion? motion, NSError? error)
 		{
+			// Motion and Error can be null: https://developer.apple.com/documentation/coremotion/cmdevicemotionhandler
+			if (error is not null)
+			{
+				if (this.Log().IsEnabled(LogLevel.Error))
+				{
+					this.Log().Error($"SimpleOrientationSensor returned error when reading Device Motion updates. {error.Description}");
+				}
+
+				return;
+			}
+
+			if (motion is null)
+			{
+				if (this.Log().IsEnabled(LogLevel.Error))
+				{
+					this.Log().Error($"SimpleOrientationSensor failed read Device Motion updates.");
+				}
+
+				return;
+			}
+
 			var orientation = ToSimpleOrientation(motion.Gravity.X, motion.Gravity.Y, motion.Gravity.Z, _threshold, _previousOrientation);
+
 			_previousOrientation = orientation;
 			SetCurrentOrientation(orientation);
 		}