monodroid_typemap_java_to_managed is failing

[jonpryor]

When recently profiling Xamarin.Android application startup, we observed lots of string allocations were being performed as part of a Object.GetObject() call:

1. Object.GetObject() >
2. TypeManager.CreateInstance() >
3. TypeManager.GetJavaToManagedType() >
4. JavaNativeTypeManager.ToCliType
5. ...

The problem is that (4) should not have happened; the only reason it happens is because the monodroid_typemap_java_to_managed() call is returning NULL, forcing us to hit a fallback path (slow! allocates many strings!):

https://github.com/xamarin/xamarin-android/blob/bb8183c8c16667b18ba9197e78294b17a0af532c/src/Mono.Android/Java.Interop/TypeManager.cs#L208-L210

We need to determine why monodroid_typemap_java_to_managed() is failing.

VS bug #635222

[radekdoulik]

There are some Java types, which lack mappings. Not many though.

Testing with xamarin-forms-samples/XamlSamples app in Release configuration.

Mappings J->M: 20 OK 11 missed 8

Missed types:

android/app/ContextImpl
android/support/v4/app/BackStackRecord
android/support/v4/app/FragmentManagerImpl
android/view/IWindow$Stub
android/view/ViewRootImpl$W
com/android/internal/os/RuntimeInit$KillApplicationHandler
com/android/internal/policy/PhoneLayoutInflater
com/android/internal/policy/PhoneWindow

Looks like some of these are not bound, like FragmentManagerImpl or BackStackRecord. Some are not even in any jar like PhoneWindow and PhoneLayoutInflater.

iMac:Release rodo$ find .|grep jar$|while read jar; do jar tf $jar; done|grep FragmentManagerImpl
android/support/v4/app/FragmentManagerImpl$StartEnterTransitionListener.class
android/support/v4/app/FragmentManagerImpl$OpGenerator.class
android/support/v4/app/FragmentManagerImpl$FragmentTag.class
android/support/v4/app/FragmentManagerImpl$1.class
android/support/v4/app/FragmentManagerImpl$AnimateOnHWLayerIfNeededListener$1.class
android/support/v4/app/FragmentManagerImpl$2.class
android/support/v4/app/FragmentManagerImpl$AnimateOnHWLayerIfNeededListener.class
android/support/v4/app/FragmentManagerImpl$PopBackStackState.class
android/support/v4/app/FragmentManagerImpl.class