How to access Activity from a React Native Android

Question

I'm attempting to bridge over the Android functionality of keeping the screen on to React Native. I figured I could do this with a simple module, however I don't know how to get access to the current Android Activity from said module.

I need the Activity reference so I can call .getWindow().addFlags(WindowManager.LayoutParams.FLAG_KEEP_SCREEN_ON); on it

I tried to get the activity via casting like so ((Activity)getReactApplicationContext().getBaseContext()), but this throws a "cannot be cast to Android.app.Activity" error

Answer 1

It's not super clear from https://github.com/facebook/react-native/blob/master/docs/NativeModulesAndroid.md, but you can read the source code of the ToastModule in the react native distribution to see how they do it github.com/facebook/react-native/blob/daba14264c9f0d29c0327440df25d81c2f58316c/ReactAndroid/src/main/java/com/facebook/react/modules/toast/ToastModule.java#L31-L33

The idea is that the main activity will be passed as the reactContext in the initializer for the module called from ReactInstanceManager.builder() call in github.com/facebook/react-native/blob/3b4845f93c296ed93c348733809845d587227823/local-cli/generator-android/templates/package/MainActivity.java#L28 via the instantiation of MainReactPackage github.com/facebook/react-native/blob/daba14264c9f0d29c0327440df25d81c2f58316c/ReactAndroid/src/main/java/com/facebook/react/shell/MainReactPackage.java#L49