[BUG] Random app crashes

[oridotaoyebode]

Description

App randomly crashes with the below stacktrace

SKTouchHandler.SetEnabled (Android.Views.View view, System.Boolean enableTouchEvents)
System.ObjectDisposedException: Cannot access a disposed object. Object name: 'SkiaSharp.Views.Android.SKCanvasView'.

Code

public class TestView: SKCanvasView
{
    public TestView()
    {
        ....

        PaintSurface += HandlePaintSurface;
        EnableTouchEvents = true;
        Touch += HandleTouch;
        
    }
}

Expected Behavior

The underling code should properly be able to set EnabledTouchEvent (or whatever platform-specific equivalent exists) without crashing.

Actual Behavior

Crash randomly by navigating through the app

Basic Information

• Version with issue: 2.80.2

• Last known good version: N/A

• IDE: Visual Studio

• Platform Target Frameworks:

  • Android: 10.0
  • iOS: 11

• Target Devices:

  • Samsung Galaxy A1
  • Hauwei P20 Pro

Detailed IDE/OS information (click to expand)

SKTouchHandler.SetEnabled (Android.Views.View view, System.Boolean enableTouchEvents)
System.ObjectDisposedException: Cannot access a disposed object. Object name: 'SkiaSharp.Views.Android.SKCanvasView'.

JniPeerMembers.AssertSelf (Java.Interop.IJavaPeerable self)
JniPeerMembers+JniInstanceMethods.InvokeVirtualVoidMethod (System.String encodedMember, Java.Interop.IJavaPeerable self, Java.Interop.JniArgumentValue* parameters)
View.SetOnTouchListener (Android.Views.View+IOnTouchListener l)
View+<>c__DisplayClass2803_0.<remove_Touch>b__0 (Android.Views.View+IOnTouchListener __v)
EventHelper.RemoveEventHandler[TInterface,TImplementor] (System.WeakReference& implementor, System.Func2[T,TResult] empty, System.Action1[T] unsetListener, System.Action1[T] remove) View.remove_Touch (System.EventHandler1[TEventArgs] value)
SKTouchHandler.SetEnabled (Android.Views.View view, System.Boolean enableTouchEvents)
SKTouchHandler.Detach (Android.Views.View view)
SKCanvasViewRendererBase`2[TFormsView,TNativeView].Dispose (System.Boolean disposing)
Object.Finalize ()

[Sebosek]

Just an idea; I don't see an implementation of IDisposable, so how do you remove the event listeners?

[EmilAlipiev]

any update on this? i am seeing also same crashes?

[oridotaoyebode]

Just an idea; I don't see an implementation of IDisposable, so how do you remove the event listeners?

Valid point. I ended up solving this. How I did it, I don't remember. Will have to check my commits

[charlesroddie]

We are also seeing these.

[charlesroddie]

Stacktrace:

Xamarin Exception Stack:
System.ObjectDisposedException: Cannot access a disposed object.
Object name: 'SkiaSharp.Views.Android.SKCanvasView'.
  at Java.Interop.JniPeerMembers.AssertSelf (Java.Interop.IJavaPeerable self) [0x00029] in <66b5e34d958f4ffd883b03b7ee0e6396>:0
  at Java.Interop.JniPeerMembers+JniInstanceMethods.InvokeVirtualVoidMethod (System.String encodedMember, Java.Interop.IJavaPeerable self, Java.Interop.JniArgumentValue* parameters) [0x00000] in <66b5e34d958f4ffd883b03b7ee0e6396>:0
  at Android.Views.View.SetOnTouchListener (Android.Views.View+IOnTouchListener l) [0x00036] in <60d11f4313494e9baf416a406e9d0d7f>:0
  at Android.Views.View+<>c__DisplayClass2963_0.<remove_Touch>b__0 (Android.Views.View+IOnTouchListener __v) [0x00000] in <60d11f4313494e9baf416a406e9d0d7f>:0
  at Java.Interop.EventHelper.RemoveEventHandler[TInterface,TImplementor] (System.WeakReference& implementor, System.Func`2[T,TResult] empty, System.Action`1[T] unsetListener, System.Action`1[T] remove) [0x00032] in <60d11f4313494e9baf416a406e9d0d7f>:0
  at Android.Views.View.remove_Touch (System.EventHandler`1[TEventArgs] value) [0x00014] in <60d11f4313494e9baf416a406e9d0d7f>:0
  at SkiaSharp.Views.Forms.SKTouchHandler.SetEnabled (Android.Views.View view, System.Boolean enableTouchEvents) [0x00003] in <6db4df16d2d546e28f83f12f7d1cc858>:0
  at SkiaSharp.Views.Forms.SKTouchHandler.Detach (Android.Views.View view) [0x00000] in <6db4df16d2d546e28f83f12f7d1cc858>:0
  at SkiaSharp.Views.Forms.SKCanvasViewRendererBase`2[TFormsView,TNativeView].Dispose (System.Boolean disposing) [0x00059] in <6db4df16d2d546e28f83f12f7d1cc858>:0
  at Java.Lang.Object.Java.Interop.IJavaPeerable.Finalized () [0x00000] in <60d11f4313494e9baf416a406e9d0d7f>:0
  at Android.Runtime.AndroidValueManager.FinalizePeer (Java.Interop.IJavaPeerable value) [0x00068] in <60d11f4313494e9baf416a406e9d0d7f>:0
  at Java.Lang.Object.Finalize () [0x0001a] in <60d11f4313494e9baf416a406e9d0d7f>:0

[charlesroddie]

@mattleibow is this likely to be looked at?

I suppose a workaround would be to make all Skia views disposable in user code and manually settting EnableTouchEvents to false on disposal.