xamarinrepro1's Introduction

Xamarin bug repro #1

In some cases, an OnTouchListener used for swipe detection can cause an ObjectDisposedException for a GestureDetector instance.

This problem only shows up when using the Tarjan GC, both with and without concurrent GC. Setting MONO_GC_PARAMS=bridge-implementation=new prevents the exception.

This seems similar to several other bugs (this one in particular). However:

This repro is occurring on Xamarin.Android, not Xamarin.Forms.
This repro is using a RecyclerView of text views, not images and not ListView like many similar bugs.
This repro uses explicit GCs to encourage the bug to manifest quickly. Hundreds of swipes are not necessary to repro.

To repro:

Start the project (on a device or emulator). You should see a list of numbers.
Scroll the list.

You should see an exception:

System.ObjectDisposedException: Cannot access a disposed object.
Object name: 'Android.Views.GestureDetector'.
  at Java.Interop.JniPeerMembers.AssertSelf (Java.Interop.IJavaPeerable self) [0x00029] in <e8c0e16a54534fa885244f0ad837c79e>:0 
  at Java.Interop.JniPeerMembers+JniInstanceMethods.InvokeVirtualBooleanMethod (System.String encodedMember, Java.Interop.IJavaPeerable self, Java.Interop.JniArgumentValue* parameters) [0x00000] in <e8c0e16a54534fa885244f0ad837c79e>:0 
  at Android.Views.GestureDetector.OnTouchEvent (Android.Views.MotionEvent ev) [0x00031] in <848bbd7c681a4975918c72f17d2f5144>:0 
  at PewBibleKjv.SwipeTouchListener.OnTouch (Android.Views.View v, Android.Views.MotionEvent e) [0x00002] in C:\\Work\\XamarinRepro1\\PewBibleKjv\\SwipeTouchListener.cs:24

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