[Bug] Regression: unhandled exception rendering charts using Xamarin Forms.

Describe the bug

Unhandled exception rendering charts using Xamarin Forms. This is a regression in version 0.9.0. Version 0.7.1 worked fine.

System.ArgumentNullException: ‘Value cannot be null. Parameter name: text’

Stack trace:

 	0xFFFFFFFFFFFFFFFF in System.Diagnostics.Debugger.Mono_UnhandledException_internal	C#	Annotated Frame
 	0x1 in System.Diagnostics.Debugger.Mono_UnhandledException at /Users/builder/jenkins/workspace/archive-mono/2020-02/android/release/mcs/class/corlib/System.Diagnostics/Debugger.cs:125,4	C#	Annotated Frame
 	0x26 in Android.Runtime.DynamicMethodNameCounter.104	C#	Annotated Frame
 	0xD in SkiaSharp.SKCanvas.DrawText	C#	Annotated Frame
 	0xD in SkiaSharp.SKCanvas.DrawText	C#	Annotated Frame
 	0x19C in Microcharts.PointChart.DrawLabels	C#	Annotated Frame
 	0x65 in Microcharts.PointChart.DrawFooter	C#	Annotated Frame
 	0x102 in Microcharts.LineChart.DrawContent	C#	Annotated Frame
 	0x29 in Microcharts.Chart.Draw	C#	Annotated Frame
 	0x35 in Microcharts.Forms.ChartView.OnPaintCanvas	C#	Annotated Frame
 	0xD in SkiaSharp.Views.Forms.SKCanvasView.OnPaintSurface	C#	Annotated Frame
 	0x2 in SkiaSharp.Views.Forms.SKCanvasView.SkiaSharp.Views.Forms.ISKCanvasViewController.OnPaintSurface	C#	Annotated Frame
 	0x21 in SkiaSharp.Views.Forms.SKCanvasViewRendererBase<SkiaSharp.Views.Forms.SKCanvasView,SkiaSharp.Views.Android.SKCanvasView>.OnPaintSurface	C#	Annotated Frame
 	0xD in SkiaSharp.Views.Android.SKCanvasView.OnPaintSurface	C#	Annotated Frame
 	0xE3 in SkiaSharp.Views.Android.SKCanvasView.OnDraw	C#	Annotated Frame
 	0x11 in Android.Views.View.n_OnDraw_Landroid_graphics_Canvas_	C#	Annotated Frame
 	0x17 in Android.Runtime.DynamicMethodNameCounter.104	C#	Annotated Frame
 	0xFFFFFFFFFFFFFFFF in Java.Interop.NativeMethods.java_interop_jnienv_call_nonvirtual_void_method_a	C#	Annotated Frame
 	0x79 in Java.Interop.JniEnvironment.InstanceMethods.CallNonvirtualVoidMethod	C#	Annotated Frame
 	0x5F in Java.Interop.JniPeerMembers.JniInstanceMethods.InvokeVirtualVoidMethod	C#	Annotated Frame
 	0x38 in Android.Views.View.Draw	C#	Annotated Frame
 	0x19 in Xamarin.Forms.Platform.Android.VisualElementRenderer<SkiaSharp.Views.Forms.SKCanvasView>.Draw at D:\a\1\s\Xamarin.Forms.Platform.Android\VisualElementRenderer.cs:402,4	C#	Annotated Frame
 	0x11 in Android.Views.View.n_Draw_Landroid_graphics_Canvas_	C#	Annotated Frame
 	0x17 in Android.Runtime.DynamicMethodNameCounter.40	C#	Annotated Frame
 	0xFFFFFFFFFFFFFFFF in Java.Interop.NativeMethods.java_interop_jnienv_call_nonvirtual_void_method_a	C#	Annotated Frame
 	0x79 in Java.Interop.JniEnvironment.InstanceMethods.CallNonvirtualVoidMethod	C#	Annotated Frame
 	0x5F in Java.Interop.JniPeerMembers.JniInstanceMethods.InvokeVirtualVoidMethod	C#	Annotated Frame
 	0x38 in Android.Views.View.Draw	C#	Annotated Frame
 	0x14 in Xamarin.Forms.Platform.Android.FastRenderers.FrameRenderer.Draw at D:\a\1\s\Xamarin.Forms.Platform.Android\FastRenderers\FrameRenderer.cs:227,4	C#	Annotated Frame
 	0x11 in Android.Views.View.n_Draw_Landroid_graphics_Canvas_	C#	Annotated Frame
 	0x17 in Android.Runtime.DynamicMethodNameCounter.40	C#	Annotated Frame
 	0xFFFFFFFFFFFFFFFF in Java.Interop.NativeMethods.java_interop_jnienv_call_nonvirtual_void_method_a	C#	Annotated Frame
 	0x79 in Java.Interop.JniEnvironment.InstanceMethods.CallNonvirtualVoidMethod	C#	Annotated Frame
 	0x5F in Java.Interop.JniPeerMembers.JniInstanceMethods.InvokeVirtualVoidMethod	C#	Annotated Frame
 	0x38 in Android.Views.View.Draw	C#	Annotated Frame
 	0x19 in Xamarin.Forms.Platform.Android.VisualElementRenderer<Xamarin.Forms.Page>.Draw at D:\a\1\s\Xamarin.Forms.Platform.Android\VisualElementRenderer.cs:402,4	C#	Annotated Frame
 	0x11 in Android.Views.View.n_Draw_Landroid_graphics_Canvas_	C#	Annotated Frame
 	0x17 in Android.Runtime.DynamicMethodNameCounter.40	C#	Annotated Frame
 	0xFFFFFFFFFFFFFFFF in Java.Interop.NativeMethods.java_interop_jnienv_call_nonvirtual_void_method_a	C#	Annotated Frame
 	0x79 in Java.Interop.JniEnvironment.InstanceMethods.CallNonvirtualVoidMethod	C#	Annotated Frame
 	0x5F in Java.Interop.JniPeerMembers.JniInstanceMethods.InvokeVirtualVoidMethod	C#	Annotated Frame
 	0x38 in Android.Views.View.Draw	C#	Annotated Frame
 	0x19 in Xamarin.Forms.Platform.Android.VisualElementRenderer<Xamarin.Forms.NavigationPage>.Draw at D:\a\1\s\Xamarin.Forms.Platform.Android\VisualElementRenderer.cs:402,4	C#	Annotated Frame
 	0x11 in Android.Views.View.n_Draw_Landroid_graphics_Canvas_	C#	Annotated Frame
 	0x17 in Android.Runtime.DynamicMethodNameCounter.40	C#	Annotated Frame

Which platform and version is this for?

Android

To Reproduce

This is a simplified version of the code I’m using to create a chart:

            List<ChartEntry> entries = new List<ChartEntry>(100);
            for (int i = 0; i < 100; i++)
            {
                double altitude = SOME POSITIVE VALUE;
                ChartEntry entry = new ChartEntry(altitude);

                if (i % 20 == 0)
                    entry.ValueLabel = altitude.ToString();

                entries.Add(entry);
            }

            LineChart chart = new LineChart
            {
                Entries = entries,
                LineMode = LineMode.Straight,
                PointMode = PointMode.None,
                MinValue = 0,
            };

Expected behavior No unhandled exceptions. Or if I’m setting the chart up wrong, an exception at setup time telling me I what I did wrong.

[mfeingol]

It appears to be fixed in 0.9.5.5. But you might want to double-check me on that.

[eman1986]

I’ve been busy with a few fires, I should be able to look into this pretty soon.