Nullable fixes in DrawingView

samples/XCT.Sample/Pages/TestCases/DrawingViewInExpanderPage.xaml

@@ -0,0 +1,25 @@
+<?xml version="1.0" encoding="utf-8" ?>
+<pages:BasePage
+    x:Class="Xamarin.CommunityToolkit.Sample.Pages.TestCases.DrawingViewInExpanderPage"
+    xmlns="http://xamarin.com/schemas/2014/forms"
+    xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
+    xmlns:pages="clr-namespace:Xamarin.CommunityToolkit.Sample.Pages"
+    xmlns:views="http://xamarin.com/schemas/2020/toolkit">
+
+    <ContentPage.Content>
+        <views:Expander>
+            <views:Expander.Header>
+                <Label Text="Click to expand" />
+            </views:Expander.Header>
+            <views:Expander.Content>
+                <views:DrawingView 
+                    HeightRequest="200"
+                    BackgroundColor="Yellow"
+                    ClearOnFinish="False"
+                    DefaultLineColor="Red" />
+            </views:Expander.Content>
+        </views:Expander>
+
+    </ContentPage.Content>
+
+</pages:BasePage>

samples/XCT.Sample/Pages/TestCases/DrawingViewInExpanderPage.xaml.cs

@@ -0,0 +1,7 @@
+namespace Xamarin.CommunityToolkit.Sample.Pages.TestCases
+{
+	public partial class DrawingViewInExpanderPage
+	{
+		public DrawingViewInExpanderPage() => InitializeComponent();
+	}
+}

samples/XCT.Sample/ViewModels/TestCases/TestCasesGalleryViewModel.cs

@@ -48,6 +48,11 @@ protected override IEnumerable<SectionModel> CreateItems() => new[]
 				typeof(SnackBarActionExceptionPage),
 				"SnackBar Action Exception",
 				"Exception in SnackBar's action doesn't crash the app."),
+
+			new SectionModel(
+				typeof(DrawingViewInExpanderPage),
+				"DrawingView in expander",
+				"DrawingView in Expander Page"),
 		};
 	}
 }

src/CommunityToolkit/Xamarin.CommunityToolkit/Views/DrawingView/Renderer/DrawingViewRenderer.android.cs

@@ -1,4 +1,5 @@
-using System.Collections.Generic;
+using System;
+using System.Collections.Generic;
 using System.ComponentModel;
 using Android.Content;
 using Android.Graphics;
@@ -78,20 +79,23 @@ protected override void OnSizeChanged(int w, int h, int oldw, int oldh)
 
 			base.OnSizeChanged(w, h, oldw, oldh);
 
-			canvasBitmap = Bitmap.CreateBitmap(w, h, Bitmap.Config.Argb8888!)!;
-			drawCanvas = new Canvas(canvasBitmap);
-			LoadLines();
+			canvasBitmap = Bitmap.CreateBitmap(w, h, Bitmap.Config.Argb8888 ?? throw new NullReferenceException("Unable to create Bitmap config"));
+			if (canvasBitmap is not null)
+			{
+				drawCanvas = new Canvas(canvasBitmap);
+				LoadLines();
+			}
 		}
 
 		protected override void OnDraw(Canvas? canvas)
 		{
 			base.OnDraw(canvas);
 
-			if (canvas is not null)
+			if (canvas is not null && canvasBitmap is not null)
 			{
 				Draw(Element.Lines, canvas);
 
-				canvas.DrawBitmap(canvasBitmap!, 0, 0, canvasPaint);
+				canvas.DrawBitmap(canvasBitmap, 0, 0, canvasPaint);
 				canvas.DrawPath(drawPath, drawPaint);
 			}
 		}
@@ -196,7 +200,7 @@ void LoadLines()
 			if (drawCanvas is null)
 				return;
 
-			drawCanvas.DrawColor(Element.BackgroundColor.ToAndroid(), PorterDuff.Mode.Clear!);
+			drawCanvas.DrawColor(Element.BackgroundColor.ToAndroid());
 			drawPath.Reset();
 			var lines = Element.Lines;
 			if (lines.Count > 0)

src/CommunityToolkit/Xamarin.CommunityToolkit/Views/DrawingView/Renderer/DrawingViewRenderer.gtk.cs

@@ -50,17 +50,17 @@ protected override void OnElementChanged(ElementChangedEventArgs<DrawingView> e)
 				SetNativeControl(vBox);
 			}
 
-			if (e.OldElement != null)
+			if (e.OldElement != null && area is not null)
 			{
-				area!.ExposeEvent -= OnDrawingAreaExposed;
+				area.ExposeEvent -= OnDrawingAreaExposed;
 				area.ButtonPressEvent -= OnMousePress;
 				area.ButtonReleaseEvent -= OnMouseRelease;
 				area.MotionNotifyEvent -= OnMouseMotion;
 			}
 
-			if (e.NewElement != null)
+			if (e.NewElement != null && area is not null)
 			{
-				area!.ExposeEvent += OnDrawingAreaExposed;
+				area.ExposeEvent += OnDrawingAreaExposed;
 				area.ButtonPressEvent += OnMousePress;
 				area.ButtonReleaseEvent += OnMouseRelease;
 				area.MotionNotifyEvent += OnMouseMotion;
@@ -82,8 +82,13 @@ protected override void OnElementPropertyChanged(object sender, PropertyChangedE
 
 		void OnDrawingAreaExposed(object source, ExposeEventArgs args)
 		{
+			if (area is null)
+			{
+				return;
+			}
+
 			Context ctx;
-			using (ctx = CairoHelper.Create(area!.GdkWindow))
+			using (ctx = CairoHelper.Create(area.GdkWindow))
 			{
 				ctx.SetSource(new SurfacePattern(surface));
 				ctx.Paint();
@@ -111,7 +116,7 @@ void OnMousePress(object source, ButtonPressEventArgs args)
 			};
 			previousPoint = point;
 			isDrawing = true;
-			area!.QueueDraw();
+			area?.QueueDraw();
 			if (!Element.MultiLineMode)
 				Element.Lines.Clear();
 		}
@@ -125,7 +130,7 @@ void OnMouseRelease(object source, ButtonReleaseEventArgs args)
 			using var ctx = new Context(surface);
 			DrawPoint(ctx, point);
 
-			area!.QueueDraw();
+			area?.QueueDraw();
 			if (currentLine != null)
 			{
 				Element.Lines.Add(currentLine);
@@ -146,19 +151,23 @@ void OnMouseMotion(object source, MotionNotifyEventArgs args)
 				using var ctx = new Context(surface);
 				DrawPoint(ctx, point);
 
-				area!.QueueDraw();
+				area?.QueueDraw();
 			}
 		}
 
 		void DrawPoint(Context ctx, PointD pointD)
 		{
-			ctx.SetSourceRGBA(currentLine!.LineColor.R, currentLine!.LineColor.G, currentLine!.LineColor.B, currentLine!.LineColor.A);
-			ctx.LineWidth = currentLine.LineWidth;
+			if (currentLine is not null)
+			{
+				ctx.SetSourceRGBA(currentLine.LineColor.R, currentLine.LineColor.G, currentLine.LineColor.B, currentLine.LineColor.A);
+				ctx.LineWidth = currentLine.LineWidth;
+				currentLine.Points.Add(new Point(pointD.X, pointD.Y));
+			}
+
 			ctx.MoveTo(previousPoint);
 			previousPoint = pointD;
 			ctx.LineTo(pointD);
-			ctx.Stroke();
-			currentLine.Points.Add(new Point(pointD.X, pointD.Y));
+			ctx.Stroke();			
 		}
 
 		void LoadPoints(ImageSurface imageSurface)
@@ -177,7 +186,7 @@ void LoadPoints(ImageSurface imageSurface)
 						foreach (var stylusPoint in stylusPoints)
 							DrawPoint(ctx, stylusPoint);
 
-						area!.QueueDraw();
+						area?.QueueDraw();
 					}
 				}
 			}
@@ -190,12 +199,16 @@ protected override void Dispose(bool disposing)
 
 			if (disposing)
 			{
-				area!.ExposeEvent -= OnDrawingAreaExposed;
-				area.ButtonPressEvent -= OnMousePress;
-				area.ButtonReleaseEvent -= OnMouseRelease;
-				area.MotionNotifyEvent -= OnMouseMotion;
-				area.Dispose();
-				surface!.Dispose();
+				if (area is not null)
+				{
+					area.ExposeEvent -= OnDrawingAreaExposed;
+					area.ButtonPressEvent -= OnMousePress;
+					area.ButtonReleaseEvent -= OnMouseRelease;
+					area.MotionNotifyEvent -= OnMouseMotion;
+					area.Dispose();
+				}
+
+				surface?.Dispose();
 				if (Element != null)
 					Element.Lines.CollectionChanged -= OnLinesCollectionChanged;
 			}
@@ -205,4 +218,4 @@ protected override void Dispose(bool disposing)
 			base.Dispose(disposing);
 		}
 	}
-}
+}

src/CommunityToolkit/Xamarin.CommunityToolkit/Views/DrawingView/Renderer/DrawingViewRenderer.ios.cs

@@ -18,8 +18,8 @@ namespace Xamarin.CommunityToolkit.UI.Views
 	/// </summary>
 	public class DrawingViewRenderer : ViewRenderer<DrawingView, UIView>
 	{
+		readonly UIBezierPath currentPath;
 		bool disposed;
-		UIBezierPath currentPath;
 		UIColor? lineColor;
 		CGPoint previousPoint;
 		Line? currentLine;
@@ -61,11 +61,11 @@ public override void TouchesBegan(NSSet touches, UIEvent? evt)
 			var touch = (UITouch)touches.AnyObject;
 			previousPoint = touch.PreviousLocationInView(this);
 			currentPath.MoveTo(previousPoint);
-			currentLine = new Line()
+			currentLine = new Line
 			{
-				Points = new ObservableCollection<Point>()
+				Points = new ObservableCollection<Point>
 				{
-					new Point(previousPoint.X, previousPoint.Y)
+					new (previousPoint.X, previousPoint.Y)
 				}
 			};
 
@@ -105,7 +105,7 @@ public override void TouchesCancelled(NSSet touches, UIEvent? evt)
 
 		public override void Draw(CGRect rect)
 		{
-			lineColor!.SetStroke();
+			lineColor?.SetStroke();
 			currentPath.Stroke();
 		}
 

src/CommunityToolkit/Xamarin.CommunityToolkit/Views/DrawingView/Renderer/DrawingViewRenderer.macos.cs

@@ -17,8 +17,8 @@ namespace Xamarin.CommunityToolkit.UI.Views
 	/// </summary>
 	public class DrawingViewRenderer : ViewRenderer<DrawingView, NSView>
 	{
+		readonly NSBezierPath currentPath;
 		bool disposed;
-		NSBezierPath currentPath;
 		NSColor? lineColor;
 		CGPoint previousPoint;
 		Line? currentLine;
@@ -58,11 +58,11 @@ public override void MouseDown(NSEvent theEvent)
 
 			previousPoint = theEvent.LocationInWindow;
 			currentPath.MoveTo(previousPoint);
-			currentLine = new Line()
+			currentLine = new Line
 			{
-				Points = new ObservableCollection<Point>()
+				Points = new ObservableCollection<Point>
 				{
-					new Point(previousPoint.X, previousPoint.Y)
+					new (previousPoint.X, previousPoint.Y)
 				}
 			};
 
@@ -94,7 +94,7 @@ public override void MouseDragged(NSEvent theEvent)
 		public override void DrawRect(CGRect dirtyRect)
 		{
 			base.DrawRect(dirtyRect);
-			lineColor!.SetStroke();
+			lineColor?.SetStroke();
 			currentPath.Stroke();
 		}
 
@@ -124,8 +124,8 @@ void UpdatePath(Line line)
 			Element.Lines.CollectionChanged -= OnLinesCollectionChanged;
 
 			var smoothedPoints = line.EnableSmoothedPath
-			? SmoothedPathWithGranularity(line.Points, line.Granularity)
-			: new ObservableCollection<Point>(line.Points);
+				? SmoothedPathWithGranularity(line.Points, line.Granularity)
+				: new ObservableCollection<Point>(line.Points);
 
 			line.Points.Clear();
 

src/CommunityToolkit/Xamarin.CommunityToolkit/Views/DrawingView/Renderer/DrawingViewRenderer.tizen.cs

@@ -36,17 +36,17 @@ protected override void OnElementChanged(ElementChangedEventArgs<DrawingView> e)
 				SetNativeControl(canvasView);
 			}
 
-			if (e.OldElement != null)
+			if (e.OldElement != null && canvasView is not null)
 			{
-				canvasView!.EvasCanvas.DeleteEventAction(EvasObjectCallbackType.MouseDown, MouseDown);
+				canvasView.EvasCanvas.DeleteEventAction(EvasObjectCallbackType.MouseDown, MouseDown);
 				canvasView.EvasCanvas.DeleteEventAction(EvasObjectCallbackType.MouseUp, MouseUp);
 				canvasView.EvasCanvas.DeleteEventAction(EvasObjectCallbackType.MouseMove, MouseMove);
 				canvasView.PaintSurface -= OnPaintSurface;
 			}
 
-			if (e.NewElement != null)
+			if (e.NewElement != null && canvasView is not null)
 			{
-				canvasView!.PaintSurface += OnPaintSurface;
+				canvasView.PaintSurface += OnPaintSurface;
 				canvasView.EvasCanvas.AddEventAction(EvasObjectCallbackType.MouseDown, MouseDown);
 				canvasView.EvasCanvas.AddEventAction(EvasObjectCallbackType.MouseUp, MouseUp);
 				canvasView.EvasCanvas.AddEventAction(EvasObjectCallbackType.MouseMove, MouseMove);
@@ -56,9 +56,9 @@ protected override void OnElementChanged(ElementChangedEventArgs<DrawingView> e)
 		protected override void OnElementPropertyChanged(object sender, PropertyChangedEventArgs e)
 		{
 			base.OnElementPropertyChanged(sender, e);
-			if (e.PropertyName == DrawingView.LinesProperty.PropertyName)
+			if (e.PropertyName == DrawingView.LinesProperty.PropertyName && canvasView is not null)
 			{
-				canvasView!.EvasCanvas.DeleteEventAction(EvasObjectCallbackType.MouseUp, MouseUp);
+				canvasView.EvasCanvas.DeleteEventAction(EvasObjectCallbackType.MouseUp, MouseUp);
 				LoadPoints();
 				canvasView.EvasCanvas.AddEventAction(EvasObjectCallbackType.MouseUp, MouseUp);
 			}
@@ -68,10 +68,10 @@ protected override void OnElementPropertyChanged(object sender, PropertyChangedE
 
 		void MouseMove()
 		{
-			if (isDrawing)
+			if (isDrawing && canvasView is not null)
 			{
-				var point = canvasView!.EvasCanvas.Pointer;
-				currentLine!.Points.Add(new Point(point.X, point.Y));
+				var point = canvasView.EvasCanvas.Pointer;
+				currentLine?.Points.Add(new Point(point.X, point.Y));
 				canvasView.Invalidate();
 			}
 		}
@@ -111,7 +111,7 @@ void LoadPoints()
 			if (Element == null)
 				return;
 
-			canvasView!.Invalidate();
+			canvasView?.Invalidate();
 		}
 
 		void DrawPath(SKCanvas canvas)
@@ -150,7 +150,11 @@ protected override void Dispose(bool disposing)
 			if (Element != null)
 			{
 				Element.Lines.CollectionChanged -= OnLinesCollectionChanged;
-				canvasView!.EvasCanvas.DeleteEventAction(EvasObjectCallbackType.MouseDown, MouseDown);
+			}
+
+			if (canvasView is not null)
+			{
+				canvasView.EvasCanvas.DeleteEventAction(EvasObjectCallbackType.MouseDown, MouseDown);
 				canvasView.EvasCanvas.DeleteEventAction(EvasObjectCallbackType.MouseUp, MouseUp);
 				canvasView.EvasCanvas.DeleteEventAction(EvasObjectCallbackType.MouseMove, MouseMove);
 				canvasView.PaintSurface -= OnPaintSurface;