Crashes with `Method Android.Runtime.AndroidEnvironmentInternal.UnhandledException(System.Exception) is inaccessible (...)` exception

[OvrBtn]

Android framework version

net9.0-android

Affected platform version

MAUI 9.0.110

Description

For some time I've been noticing random crashes for some % of users with this stacktrace

System.MethodAccessException: Method `Android.Runtime.AndroidEnvironmentInternal.UnhandledException(System.Exception)' is inaccessible from method `AndroidX.Fragment.App.Fragment.n_OnCreateView_Landroid_view_LayoutInflater_Landroid_view_ViewGroup_Landroid_os_Bundle__mm_wrapper(intptr,intptr,intptr,intptr,intptr)'
   at AndroidX.Fragment.App.Fragment.n_OnCreateView_Landroid_view_LayoutInflater_Landroid_view_ViewGroup_Landroid_os_Bundle__mm_wrapper(IntPtr jnienv, IntPtr native__this, IntPtr native_inflater, IntPtr native_container, IntPtr native_savedInstanceState)

Since it's happening in release mode and I can't reproduce it it's hard to say anything more about it.

Don't know how useful that would be but the first time I got a log with this error was on 06/17/2025 but I can't tell if it's due to some changes in MAUI/net-android or in my configuration

Steps to Reproduce

Did you find any workaround?

No response

Relevant log output

[jonpryor]

I believe this is a bug in the marshal method rewriter.

See also:

• android/src/Xamarin.Android.Build.Tasks/Utilities/MarshalMethodsAssemblyRewriter.cs

  Lines 60 to 62 in e397464

  	MethodDefinition? unhandledExceptionMethod = FindMethod (androidEnvironment, "UnhandledException", required: true);
  	if (unhandledExceptionMethod == null)
  	throw new ArgumentNullException (nameof (unhandledExceptionMethod));

• android/src/Mono.Android/Android.Runtime/AndroidEnvironment.cs

  Line 110 in e397464

  internal static void UnhandledException (Exception e)

• 8bc7a3e

In particular from commit 8bc7a3e:

The n_…_mm_wrapper() method is responsible for exception marshaling
and for bool marshaling. The n_…_mm_wrapper() method has the
[UnmanagedCallersOnlyAttribute][5], and works by calling the
existing n_…() method:

	namespace Android.App {
	    public partial class Activity {

	        // Added
	        [UnmanagedCallersOnly]
	        static void n_OnCreate_Landroid_os_Bundle__mm_wrapper (IntPtr jnienv, IntPtr native__this, IntPtr native_savedInstanceState)
	        {
	            try {
	                n_OnCreate_Landroid_os_Bundle_ (jnienv, native__this, native_savedInstanceState);
	            }
	            catch (Exception __e) {
	                Android.Runtime.AndroidEnvironmentInternal.UnhandledException (__e);
	            }
	        }
	    }
	}

Note the generated catch (Exception __e) block, which contains an invocation of AndroidEnvironmentInternal.UnhandledException(__e). The problem is that AndroidEnvironmentInternal.UnhandledException() is internal, and thus cannot be used from outside of the calling assembly or [InternalsVisibleTo] assemblies, which would thus include the main app.

[jonpryor]

A possible fix would be for the marshal method rewriter to make AndroidEnvironmentInternal.UnhandledException() public, or to have it invoke a public method.

Also note that the marshal method rewriter shouldn't need to do anything to .NET 10-based marshal methods, due to:

• dotnet/java-interop@356485e
• dotnet/java-interop@57f7bc8

[jonpryor]

Also interesting: #9081 (comment)

[OvrBtn]

I've been talking with @jonpryor on Discord and he suggested that disabling marshal methods would help (I had them previously explicitly set to true in .csproj).

Yesterday I've released a version with AndroidEnableMarshalMethods set to false and I've already received first log for this new version of crash with this weird error so maybe it's not marshal methods?

If that would be of any help here is my current .csproj https://github.com/OvrBtn/StudentUsos/blob/main/StudentUsos/StudentUsos.csproj

[grendello]

@OvrBtn the OP trace definitely suggests a connection to marshal methods (the _mm_wrapper prefix indicates a marshal methods wrapper in use), so that's at least one scenario.
As for your new release, can you attach here the lib/arm64-v8a/libassemblies.arm64-v8a.blob.so file from your apk, please?
It would also be useful to see the stack trace from the new version crash. Thanks!

[OvrBtn]

@grendello github doesn't support .so files here so I've uploaded it to google drive https://drive.google.com/file/d/1qRxjeFXUSHe7CkD7-FcyIQG4dNAMoTii/view?usp=sharing
Alternatively I have public .apk in github releases, the versions with <AndroidEnableMarshalMethods>false</AndroidEnableMarshalMethods> is 4.4.0.

Also the exception message from this newest version is

System.MethodAccessException: Method `Android.Runtime.AndroidEnvironmentInternal.UnhandledException(System.Exception)' is inaccessible from method `AndroidX.Fragment.App.Fragment.n_OnCreateView_Landroid_view_LayoutInflater_Landroid_view_ViewGroup_Landroid_os_Bundle__mm_wrapper(intptr,intptr,intptr,intptr,intptr)'
   at AndroidX.Fragment.App.Fragment.n_OnCreateView_Landroid_view_LayoutInflater_Landroid_view_ViewGroup_Landroid_os_Bundle__mm_wrapper(IntPtr jnienv, IntPtr native__this, IntPtr native_inflater, IntPtr native_container, IntPtr native_savedInstanceState)

[grendello]

@OvrBtn cool, thanks for the .so and the trace! I wanted to confirm that Mono.Android.Runtime.dll is packaged in your app, and it is. However, looking at the latest trace, you are still using marshal methods - otherwise we wouldn't see the __mm_wrapper suffix. Seems like something overrode your <AndroidEnableMarshalMethods>false</AndroidEnableMarshalMethods> setting? Build your app from a clean state (after removing bin and obj) and record a binlog (-bl command line parameter to dotnet build) and see what is the actual value of AndroidEnableMarshalMethods property.