Detect PointCollection changes in Polyline and Polygon (#11579) fixes #11848

Xamarin.Forms.Controls.Issues/Xamarin.Forms.Controls.Issues.Shared/Issue11563.cs

@@ -36,12 +36,18 @@ namespace Xamarin.Forms.Controls.Issues
 				Text = "Tap the button, if the Polygon is updated, the test has passed."
 			};
 
-			var button = new Button
+			var updatePointsButton = new Button
 			{
-				Text = "Update Polygon points"
+				Text = "Update points"
 			};
 
-			var points = new PointCollection() { new Point(10, 10), new Point(100, 50), new Point(100, 95), new Point(10, 95) };
+			var updatePointsCollectionButton = new Button
+			{
+				Text = "Update points collection"
+			};
+
+			var points1 = new PointCollection() { new Point(10, 10), new Point(100, 50), new Point(100, 95), new Point(10, 95) };
+			var points2 = new PointCollection() { new Point(10, 5), new Point(100, 70), new Point(100, 95), new Point(10, 95) };
 
 			var polygon = new Polygon
 			{
@@ -49,19 +55,28 @@ namespace Xamarin.Forms.Controls.Issues
 				WidthRequest = 100,
 				StrokeThickness = 2,
 				Stroke = Brush.Red,
-				Points = points
+				Points = points1
 			};
 
 			layout.Children.Add(instructions);
-			layout.Children.Add(button);
+			layout.Children.Add(updatePointsButton);
+			layout.Children.Add(updatePointsCollectionButton);
 			layout.Children.Add(polygon);
 
 			Content = layout;
 
-			button.Clicked += (sender, args) =>
+			updatePointsButton.Clicked += (sender, args) =>
 			{
-				if (points.Count > 1)
-					points.RemoveAt(1);
+				if (points1.Count > 1)
+					points1.RemoveAt(1);
+
+				if (points2.Count > 1)
+					points2.RemoveAt(1);
+			};
+
+			updatePointsCollectionButton.Clicked += (sender, args) =>
+			{
+				polygon.Points = points2;
 			};
 		}
 	}

Xamarin.Forms.Platform.Android/Shapes/PolygonRenderer.cs

@@ -9,6 +9,8 @@ namespace Xamarin.Forms.Platform.Android
 {
 	public class PolygonRenderer : ShapeRenderer<Polygon, PolygonView>
 	{
+		PointCollection _points;
+
 		public PolygonRenderer(Context context) : base(context)
 		{
 
@@ -25,9 +27,6 @@ namespace Xamarin.Forms.Platform.Android
 
 			if (args.NewElement != null)
 			{
-				var points = args.NewElement.Points;
-				points.CollectionChanged += OnCollectionChanged;
-
 				UpdatePoints();
 				UpdateFillRule();
 			}
@@ -49,17 +48,24 @@ namespace Xamarin.Forms.Platform.Android
 
 			if (disposing)
 			{
-				if (Element != null)
+				if (_points != null)
 				{
-					var points = Element.Points;
-					points.CollectionChanged -= OnCollectionChanged;
+					_points.CollectionChanged -= OnCollectionChanged;
+					_points = null;
 				}
 			}
 		}
 
 		void UpdatePoints()
 		{
-			Control.UpdatePoints(Element.Points);
+			if (_points != null)
+				_points.CollectionChanged -= OnCollectionChanged;
+
+			_points = Element.Points;
+
+			_points.CollectionChanged += OnCollectionChanged;
+
+			Control.UpdatePoints(_points);
 		}
 
 		void UpdateFillRule()

Xamarin.Forms.Platform.Android/Shapes/PolylineRenderer.cs

@@ -1,4 +1,5 @@
-using System.ComponentModel;
+using System.Collections.Specialized;
+using System.ComponentModel;
 using Android.Content;
 using Xamarin.Forms.Shapes;
 using static Android.Graphics.Path;
@@ -8,6 +9,8 @@ namespace Xamarin.Forms.Platform.Android
 {
 	public class PolylineRenderer : ShapeRenderer<Polyline, PolylineView>
 	{
+		PointCollection _points;
+
 		public PolylineRenderer(Context context) : base(context)
 		{
 
@@ -39,15 +42,41 @@ namespace Xamarin.Forms.Platform.Android
 				UpdateFillRule();
 		}
 
+		protected override void Dispose(bool disposing)
+		{
+			base.Dispose(disposing);
+
+			if (disposing)
+			{
+				if (_points != null)
+				{
+					_points.CollectionChanged -= OnCollectionChanged;
+					_points = null;
+				}
+			}
+		}
+
 		void UpdatePoints()
 		{
-			Control.UpdatePoints(Element.Points);
+			if (_points != null)
+				_points.CollectionChanged -= OnCollectionChanged;
+
+			_points = Element.Points;
+
+			_points.CollectionChanged += OnCollectionChanged;
+
+			Control.UpdatePoints(_points);
 		}
 
 		void UpdateFillRule()
 		{
 			Control.UpdateFillMode(Element.FillRule == FillRule.Nonzero);
 		}
+
+		void OnCollectionChanged(object sender, NotifyCollectionChangedEventArgs e)
+		{
+			UpdatePoints();
+		}
 	}
 
 	public class PolylineView : ShapeView

Xamarin.Forms.Platform.UAP/Shapes/PolygonRenderer.cs

@@ -17,6 +17,8 @@ namespace Xamarin.Forms.Platform.WPF
 {
 	public class PolygonRenderer : ShapeRenderer<Polygon, WPolygon>
 	{
+		PointCollection _points;
+
 		protected override void OnElementChanged(ElementChangedEventArgs<Polygon> args)
 		{
 			if (Control == null && args.NewElement != null)
@@ -52,17 +54,24 @@ namespace Xamarin.Forms.Platform.WPF
 
 			if (disposing)
 			{
-				if (Element != null)
+				if (_points != null)
 				{
-					var points = Element.Points;
-					points.CollectionChanged -= OnCollectionChanged;
+					_points.CollectionChanged -= OnCollectionChanged;
+					_points = null;
 				}
 			}
 		}
 
 		void UpdatePoints()
 		{
-			Control.Points = Element.Points.ToWindows();
+			if (_points != null)
+				_points.CollectionChanged -= OnCollectionChanged;
+
+			_points = Element.Points;
+
+			_points.CollectionChanged += OnCollectionChanged;
+
+			Control.Points = _points.ToWindows();
 		}
 
 		void UpdateFillRule()

Xamarin.Forms.Platform.UAP/Shapes/PolylineRenderer.cs

@@ -1,5 +1,6 @@
 using System.ComponentModel;
 using Xamarin.Forms.Shapes;
+using System.Collections.Specialized;
 
 #if WINDOWS_UWP
 using WFillRule = Windows.UI.Xaml.Media.FillRule;
@@ -16,6 +17,8 @@ namespace Xamarin.Forms.Platform.WPF
 {
 	public class PolylineRenderer : ShapeRenderer<Polyline, WPolyline>
 	{
+		PointCollection _points;
+
 		protected override void OnElementChanged(ElementChangedEventArgs<Polyline> args)
 		{
 			if (Control == null && args.NewElement != null)
@@ -42,9 +45,30 @@ namespace Xamarin.Forms.Platform.WPF
 				UpdateFillRule();
 		}
 
+		protected override void Dispose(bool disposing)
+		{
+			base.Dispose(disposing);
+
+			if (disposing)
+			{
+				if (_points != null)
+				{
+					_points.CollectionChanged -= OnCollectionChanged;
+					_points = null;
+				}
+			}
+		}
+
 		void UpdatePoints()
 		{
-			Control.Points = Element.Points.ToWindows();
+			if (_points != null)
+				_points.CollectionChanged -= OnCollectionChanged;
+
+			_points = Element.Points;
+
+			_points.CollectionChanged += OnCollectionChanged;
+
+			Control.Points = _points.ToWindows();
 		}
 
 		void UpdateFillRule()
@@ -53,5 +77,10 @@ namespace Xamarin.Forms.Platform.WPF
 				WFillRule.EvenOdd :
 				WFillRule.Nonzero;
 		}
+
+		void OnCollectionChanged(object sender, NotifyCollectionChangedEventArgs e)
+		{
+			UpdatePoints();
+		}
 	}
 }

Xamarin.Forms.Platform.iOS/Shapes/PolygonRenderer.cs

@@ -11,6 +11,8 @@ namespace Xamarin.Forms.Platform.MacOS
 {
     public class PolygonRenderer : ShapeRenderer<Polygon, PolygonView>
     {
+        PointCollection _points;
+
         [Internals.Preserve(Conditional = true)]
         public PolygonRenderer()
         {
@@ -36,7 +38,7 @@ namespace Xamarin.Forms.Platform.MacOS
             }
         }
 
-		protected override void OnElementPropertyChanged(object sender, PropertyChangedEventArgs args)
+        protected override void OnElementPropertyChanged(object sender, PropertyChangedEventArgs args)
         {
             base.OnElementPropertyChanged(sender, args);
 
@@ -46,23 +48,30 @@ namespace Xamarin.Forms.Platform.MacOS
                 UpdateFillRule();
         }
 
-		protected override void Dispose(bool disposing)
-		{
-			base.Dispose(disposing);
+        protected override void Dispose(bool disposing)
+        {
+            base.Dispose(disposing);
 
             if (disposing)
             {
-                if (Element != null)
+                if (_points != null)
                 {
-                    var points = Element.Points;
-                    points.CollectionChanged -= OnCollectionChanged;
+                    _points.CollectionChanged -= OnCollectionChanged;
+                    _points = null;
                 }
             }
-		}
+        }
 
-		void UpdatePoints()
+        void UpdatePoints()
         {
-            Control.UpdatePoints(Element.Points.ToCGPoints());
+            if (_points != null)
+                _points.CollectionChanged -= OnCollectionChanged;
+
+            _points = Element.Points;
+
+            _points.CollectionChanged += OnCollectionChanged;
+
+            Control.UpdatePoints(_points.ToCGPoints());
         }
 
         public void UpdateFillRule()

Xamarin.Forms.Platform.iOS/Shapes/PolylineRenderer.cs

@@ -1,4 +1,5 @@
-using System.ComponentModel;
+using System.Collections.Specialized;
+using System.ComponentModel;
 using CoreGraphics;
 using Xamarin.Forms.Shapes;
 
@@ -10,6 +11,8 @@ namespace Xamarin.Forms.Platform.MacOS
 {
     public class PolylineRenderer : ShapeRenderer<Polyline, PolylineView>
     {
+        PointCollection _points;
+
         [Internals.Preserve(Conditional = true)]
         public PolylineRenderer()
         {
@@ -42,22 +45,48 @@ namespace Xamarin.Forms.Platform.MacOS
                 UpdateFillRule();
         }
 
+        protected override void Dispose(bool disposing)
+        {
+            base.Dispose(disposing);
+
+            if (disposing)
+            {
+                if (_points != null)
+                {
+                    _points.CollectionChanged -= OnCollectionChanged;
+                    _points = null;
+                }
+            }
+        }
+
         void UpdatePoints()
         {
-            Control.UpdatePoints(Element.Points.ToCGPoints());
+            if (_points != null)
+                _points.CollectionChanged -= OnCollectionChanged;
+
+            _points = Element.Points;
+
+            _points.CollectionChanged += OnCollectionChanged;
+
+            Control.UpdatePoints(_points.ToCGPoints());
         }
 
         public void UpdateFillRule()
         {
             Control.UpdateFillMode(Element.FillRule == FillRule.Nonzero);
         }
+
+        void OnCollectionChanged(object sender, NotifyCollectionChangedEventArgs e)
+        {
+            UpdatePoints();
+        }
     }
 
     public class PolylineView : ShapeView
     {
         public void UpdatePoints(CGPoint[] points)
         {
-			var path = new CGPath();
+            var path = new CGPath();
             path.AddLines(points);
             ShapeLayer.UpdateShape(path);
         }
@@ -67,4 +96,4 @@ namespace Xamarin.Forms.Platform.MacOS
             ShapeLayer.UpdateFillMode(fillMode);
         }
     }
-}
+}