Add Android support

[tomduncalf]

This PR adds Android support, by refactoring the existing module code into a shared location and adding the necessary CMake config, JNI method and Java call to install the JSI native module on Android.

There is one issue, which I have no idea how to solve: in debug mode, there are a load of exceptions of type SIGUSR1 which happen. If you just click "continue", the app still works, but it's a bit weird - perhaps someone involved in React and JSI could take a look at this PR and give their feedback?

[ericlewis]

@tomduncalf refactor this & I’ll merge! Unless you prefer it left open.

[tomduncalf]

Done! Happy to merge it, but if you know anyone at Facebook who you could point in this direction to take a look at the exception I get in debug (and more generally if this is the right approach), that would be great :)

[axemclion]

Internally also, this is where we install the JSI Modules.

If you are just exposing native methods, why not use React Native's TurboModuleManager - whose intenet is pretty much that ?

[tomduncalf]

To be honest I wasn’t sure if TurboModules were ready to use or not! If they are it would be awesome to see an example of how to use them :)

[terrysahaidak]

@axemclion could you please provide an example on how to use turbo modules in that case?

[axemclion]

In React native's case, you can use fbjni, which helps out with types i nJNI. Check out TurboModuleManager.cpp.

This code is similar to what we do there.

[tomduncalf]

Yeah this is where I copied it from, I think – or are you suggesting using TurboModuleManager directly?

[axemclion]

Also curious why the xcode project changed here ?

[gaurav107]

file moved: ios/TestBinding.cpp → c++/TestBinding.cpp

[tomduncalf]

Correct, sorry I missed your message @axemclion!

[drafish]

Build failed with an exception

/Users/drafish/workspace/react-native-hostobject-demo/c++/TestBinding.cpp:12:46: error: no member named 'react' in namespace 'facebook'
        auto test = std::make_unique<facebook::react::Test>();
                                     ~~~~~~~~~~^
  /Users/drafish/workspace/react-native-hostobject-demo/c++/TestBinding.cpp:13:53: error: no member named 'react' in namespace 'facebook'
        auto testBinding = std::make_shared<facebook::react::TestBinding>(std::move(test));
                                            ~~~~~~~~~~^

replace facebook::react with example

BUILD SUCCESSFUL