[Mono.Android] update JNIEnv.FindClass() to use JniEnvironment.Types.FindClass()

[jonathanpeppers]

This avoids the problem of JNIEnvInit.mid_Class_forName being null in a NativeAOT context:

02-07 14:05:25.954 30744 30744 E AndroidRuntime: Process: net.dot.hellonativeaot, PID: 30744
02-07 14:05:25.954 30744 30744 E AndroidRuntime: net.dot.jni.internal.JavaProxyThrowable: System.TypeInitializationException: TypeInitialization_Type_NoTypeAvailable
02-07 14:05:25.954 30744 30744 E AndroidRuntime:  ---> System.ArgumentNullException: ArgumentNull_Generic Arg_ParamName_Name, method
02-07 14:05:25.954 30744 30744 E AndroidRuntime:    at Java.Interop.JniEnvironment.StaticMethods.CallStaticObjectMethod(JniObjectReference, JniMethodInfo, JniArgumentValue*) + 0x1c8
02-07 14:05:25.954 30744 30744 E AndroidRuntime:    at Android.Runtime.JNIEnv.FindClass(String) + 0xb4
02-07 14:05:25.954 30744 30744 E AndroidRuntime:    at Java.Lang.Class..cctor() + 0x7c
02-07 14:05:25.954 30744 30744 E AndroidRuntime:    at System.Runtime.CompilerServices.ClassConstructorRunner.EnsureClassConstructorRun(StaticClassConstructionContext*) + 0xb4
02-07 14:05:25.954 30744 30744 E AndroidRuntime:    Exception_EndOfInnerExceptionStack
02-07 14:05:25.954 30744 30744 E AndroidRuntime:    at System.Runtime.CompilerServices.ClassConstructorRunner.EnsureClassConstructorRun(StaticClassConstructionContext*) + 0x160
02-07 14:05:25.954 30744 30744 E AndroidRuntime:    at System.Runtime.CompilerServices.ClassConstructorRunner.CheckStaticClassConstructionReturnNonGCStaticBase(StaticClassConstructionContext*, IntPtr) + 0x14
02-07 14:05:25.954 30744 30744 E AndroidRuntime:    at Android.Runtime.JNIEnv.FindClass(String) + 0xc0
02-07 14:05:25.954 30744 30744 E AndroidRuntime:    at Android.App.Application.get_Context() + 0x50
02-07 14:05:25.954 30744 30744 E AndroidRuntime:    at Microsoft.Maui.Hosting.EssentialsExtensions.<>c.<UseEssentials>b__0_0(ILifecycleBuilder life) + 0x18
02-07 14:05:25.954 30744 30744 E AndroidRuntime:    at Microsoft.Maui.LifecycleEvents.LifecycleEventService..ctor(IEnumerable`1) + 0x94
02-07 14:05:25.954 30744 30744 E AndroidRuntime:    at Microsoft.Maui.LifecycleEvents.MauiAppHostBuilderExtensions.<>c.<ConfigureLifecycleEvents>b__0_0(IServiceProvider sp) + 0x3c
02-07 14:05:25.954 30744 30744 E AndroidRuntime:    at Microsoft.Extensions.DependencyInjection.ServiceLookup.CallSiteRuntimeResolver.VisitRootCache(ServiceCallSite, RuntimeResolverContext) + 0x68
02-07 14:05:25.954 30744 30744 E AndroidRuntime:    at Microsoft.Extensions.DependencyInjection.ServiceProvider.CreateServiceAccessor(ServiceIdentifier serviceIdentifier) + 0x180
02-07 14:05:25.954 30744 30744 E AndroidRuntime:    at System.Collections.Concurrent.ConcurrentDictionary`2.GetOrAdd(TKey, Func`2) + 0x11c
02-07 14:05:25.954 30744 30744 E AndroidRuntime:    at Microsoft.Extensions.DependencyInjection.ServiceProvider.GetService(ServiceIdentifier, ServiceProviderEngineScope) + 0x44
02-07 14:05:25.954 30744 30744 E AndroidRuntime:    at Microsoft.Maui.MauiContext.WrappedServiceProvider.GetService(Type) + 0x48
02-07 14:05:25.954 30744 30744 E AndroidRuntime:    at Microsoft.Maui.MauiContext.WrappedServiceProvider.GetService(Type) + 0x48
02-07 14:05:25.954 30744 30744 E AndroidRuntime:    at Microsoft.Extensions.DependencyInjection.ServiceProviderServiceExtensions.GetService[T](IServiceProvider) + 0x3c
02-07 14:05:25.954 30744 30744 E AndroidRuntime:    at Microsoft.Maui.LifecycleEvents.LifecycleEventServiceExtensions.<GetLifecycleEventDelegates>d__3`1.MoveNext() + 0x38
02-07 14:05:25.954 30744 30744 E AndroidRuntime:    at Microsoft.Maui.LifecycleEvents.LifecycleEventServiceExtensions.InvokeLifecycleEvents[TDelegate](IServiceProvider, Action`1) + 0x68
02-07 14:05:25.954 30744 30744 E AndroidRuntime:    at Microsoft.Maui.MauiApplication.OnCreate() + 0xb0
02-07 14:05:25.954 30744 30744 E AndroidRuntime:    at Android.App.Application.n_OnCreate(IntPtr jnienv, IntPtr native__this) + 0xb0
02-07 14:05:25.954 30744 30744 E AndroidRuntime: at my.MainApplication.n_onCreate(Native Method)
02-07 14:05:25.954 30744 30744 E AndroidRuntime: at my.MainApplication.onCreate(MainApplication.java:24)
02-07 14:05:25.954 30744 30744 E AndroidRuntime: at android.app.Instrumentation.callApplicationOnCreate(Instrumentation.java:1386)
02-07 14:05:25.954 30744 30744 E AndroidRuntime: at android.app.ActivityThread.handleBindApplication(ActivityThread.java:7398)
02-07 14:05:25.954 30744 30744 E AndroidRuntime: at android.app.ActivityThread.-$$Nest$mhandleBindApplication(Unknown Source:0)
02-07 14:05:25.954 30744 30744 E AndroidRuntime: at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2379)
02-07 14:05:25.954 30744 30744 E AndroidRuntime: at android.os.Handler.dispatchMessage(Handler.java:107)
02-07 14:05:25.954 30744 30744 E AndroidRuntime: at android.os.Looper.loopOnce(Looper.java:232)
02-07 14:05:25.954 30744 30744 E AndroidRuntime: at android.os.Looper.loop(Looper.java:317)
02-07 14:05:25.954 30744 30744 E AndroidRuntime: at android.app.ActivityThread.main(ActivityThread.java:8592)
02-07 14:05:25.954 30744 30744 E AndroidRuntime: at java.lang.reflect.Method.invoke(Native Method)
02-07 14:05:25.954 30744 30744 E AndroidRuntime: at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:580)
02-07 14:05:25.954 30744 30744 E AndroidRuntime: at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:878)

This also allows us to remove these that are now unused:

• JnienvInitializeArgs.Class_forName
• JNIEnv.BinaryName()

[jonathanpeppers]

I found this old issue:

• Switch JniEnvironment.FindClass to use Class.forName instead of ClassLoader.loadClass java-interop#23

Which isn't done yet in Java.Interop, is that important?

• https://github.com/dotnet/java-interop/blob/6bc87e8b55bc00ae1423a5ae92cf5db573fc76ed/src/Java.Interop/Java.Interop/JniEnvironment.Types.cs#L60-L65

[jonpryor]

@jonathanpeppers asked:

Which isn't done yet in Java.Interop, is that important?

Good question! I forget.

This is the commit which migrated Mono.Android.dll to using Class.forName():

https://github.com/xamarin/monodroid/commit/ed984a3a0bfbe71f6499a7855c647b5bc2b28466

[Mono.Android] Switch JNIEnv.FindClass to use Class.forName

Previously, JNIEnv.FindClass(string) would defer to ClassLoader.loadClass to load a Java type.

Because loading some classes on Java is a bit of an arcane art, you have to use a special syntax for
primitive types. This syntax seemed to have been supported just fine on (Dalvik|ART) when using the
loadClass method but on a desktop java like the Oracle VM this is not the case anymore.

Instead, passing by the Class.forName static method seems to handle such case that involves primitive
types so this commit supply the necessary handles to JNIEnv from native and switch the FindClass method
to use them.

For instance, a type that used to trip the runtime beforehand with a ClassNotFoundException but doesn't
after this commit is '[I' (an array of primitive Java integer).

Note: this commit only fix the XA part, Java.Interop implements the same sort of type lookup and needs to
be ultimately updated to the same technique at a later stage.

This appears to have been for the Xamarin.Android Designer atop desktop Java, which is something we no longer support.

We may want to migrate to Class.forName() anyway, but this doesn't appear to be important right now.

[jonpryor]

Draft commit message:

Context: https://github.com/xamarin/monodroid/commit/ed984a3a0bfbe71f6499a7855c647b5bc2b28466
Context: https://github.com/dotnet/java-interop/issues/23

Update `JNIEnv.FindClass()` to use `JniEnvironment.Types.FindClass()`.

This avoids the problem of `JNIEnvInit.mid_Class_forName` being
`null` in a NativeAOT context:

	E AndroidRuntime: Process: net.dot.hellonativeaot, PID: 30744
	E AndroidRuntime: net.dot.jni.internal.JavaProxyThrowable: System.TypeInitializationException: TypeInitialization_Type_NoTypeAvailable
	E AndroidRuntime:  ---> System.ArgumentNullException: ArgumentNull_Generic Arg_ParamName_Name, method
	E AndroidRuntime:    at Java.Interop.JniEnvironment.StaticMethods.CallStaticObjectMethod(JniObjectReference, JniMethodInfo, JniArgumentValue*) + 0x1c8
	E AndroidRuntime:    at Android.Runtime.JNIEnv.FindClass(String) + 0xb4
	E AndroidRuntime:    at Java.Lang.Class..cctor() + 0x7c
	E AndroidRuntime:    at System.Runtime.CompilerServices.ClassConstructorRunner.EnsureClassConstructorRun(StaticClassConstructionContext*) + 0xb4
	E AndroidRuntime:    Exception_EndOfInnerExceptionStack
	E AndroidRuntime:    at System.Runtime.CompilerServices.ClassConstructorRunner.EnsureClassConstructorRun(StaticClassConstructionContext*) + 0x160
	E AndroidRuntime:    at System.Runtime.CompilerServices.ClassConstructorRunner.CheckStaticClassConstructionReturnNonGCStaticBase(StaticClassConstructionContext*, IntPtr) + 0x14
	E AndroidRuntime:    at Android.Runtime.JNIEnv.FindClass(String) + 0xc0
	E AndroidRuntime:    at Android.App.Application.get_Context() + 0x50
	E AndroidRuntime:    at Microsoft.Maui.Hosting.EssentialsExtensions.<>c.<UseEssentials>b__0_0(ILifecycleBuilder life) + 0x18
	E AndroidRuntime:    at Microsoft.Maui.LifecycleEvents.LifecycleEventService..ctor(IEnumerable`1) + 0x94
	E AndroidRuntime:    at Microsoft.Maui.LifecycleEvents.MauiAppHostBuilderExtensions.<>c.<ConfigureLifecycleEvents>b__0_0(IServiceProvider sp) + 0x3c
	E AndroidRuntime:    at Microsoft.Extensions.DependencyInjection.ServiceLookup.CallSiteRuntimeResolver.VisitRootCache(ServiceCallSite, RuntimeResolverContext) + 0x68
	E AndroidRuntime:    at Microsoft.Extensions.DependencyInjection.ServiceProvider.CreateServiceAccessor(ServiceIdentifier serviceIdentifier) + 0x180
	E AndroidRuntime:    at System.Collections.Concurrent.ConcurrentDictionary`2.GetOrAdd(TKey, Func`2) + 0x11c
	E AndroidRuntime:    at Microsoft.Extensions.DependencyInjection.ServiceProvider.GetService(ServiceIdentifier, ServiceProviderEngineScope) + 0x44
	E AndroidRuntime:    at Microsoft.Maui.MauiContext.WrappedServiceProvider.GetService(Type) + 0x48
	E AndroidRuntime:    at Microsoft.Maui.MauiContext.WrappedServiceProvider.GetService(Type) + 0x48
	E AndroidRuntime:    at Microsoft.Extensions.DependencyInjection.ServiceProviderServiceExtensions.GetService[T](IServiceProvider) + 0x3c
	E AndroidRuntime:    at Microsoft.Maui.LifecycleEvents.LifecycleEventServiceExtensions.<GetLifecycleEventDelegates>d__3`1.MoveNext() + 0x38
	E AndroidRuntime:    at Microsoft.Maui.LifecycleEvents.LifecycleEventServiceExtensions.InvokeLifecycleEvents[TDelegate](IServiceProvider, Action`1) + 0x68
	E AndroidRuntime:    at Microsoft.Maui.MauiApplication.OnCreate() + 0xb0
	E AndroidRuntime:    at Android.App.Application.n_OnCreate(IntPtr jnienv, IntPtr native__this) + 0xb0
	E AndroidRuntime: at my.MainApplication.n_onCreate(Native Method)
	E AndroidRuntime: at my.MainApplication.onCreate(MainApplication.java:24)
	E AndroidRuntime: at android.app.Instrumentation.callApplicationOnCreate(Instrumentation.java:1386)
	E AndroidRuntime: at android.app.ActivityThread.handleBindApplication(ActivityThread.java:7398)
	E AndroidRuntime: at android.app.ActivityThread.-$$Nest$mhandleBindApplication(Unknown Source:0)
	E AndroidRuntime: at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2379)
	E AndroidRuntime: at android.os.Handler.dispatchMessage(Handler.java:107)
	E AndroidRuntime: at android.os.Looper.loopOnce(Looper.java:232)
	E AndroidRuntime: at android.os.Looper.loop(Looper.java:317)
	E AndroidRuntime: at android.app.ActivityThread.main(ActivityThread.java:8592)
	E AndroidRuntime: at java.lang.reflect.Method.invoke(Native Method)
	E AndroidRuntime: at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:580)
	E AndroidRuntime: at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:878)

This also allows us to remove these fields that are now unused:

  * `JnienvInitializeArgs.Class_forName`
  * `JNIEnv.BinaryName()`

TODO?  While `JNIEnv.FindClass()` was using [`Class.forName()`][0],
`JniEnvironment.Types.FindClass()` uses [`ClassLoader.loadClass()`][1].
`JNIEnv.FindClass()` originally used `ClassLoader.loadClass()`, but
was changed to use `Class.forName()` in xamarin/monodroid@ed984a3a as
part of supporting the Xamarin.Android Designer.

Updating `JNIEnv.FindClass()` to use `JniEnvironment.Types.FindClass()`
effectively reverts that original change.  This is "fine" for now --
the Xamarin.Android Designer is no longer supported -- but in the
future we may want to update `JniEnvironment.Types.FindClass()` to
use `Class.forName()`; see dotnet/java-interop#23.

[0]: https://developer.android.com/reference/java/lang/Class#forName(java.lang.String)
[1]: https://developer.android.com/reference/java/lang/ClassLoader#loadClass(java.lang.String)

[filipnavara]

We may want to migrate to Class.forName() anyway, but this doesn't appear to be important right now.

The observable difference is that Class.forName runs static constructors. That could possibly be quite important I guess.