TL;DR: Native Java code is still better than NativeScript or React.
It largely depends on your application requirements as well as business requirements. If you want cross platform app developed quickly and you are low on engineering resources, React or Native might seem more appealing.
However, once you are deep into the app, you'll want to write in native java. Sometimes there are problems with 3rd party integrations and the generated app and once a bug is on your production app in Play Store, it might will be mighty difficult to get most of your existing users to update to the new version. Since this isn't web, even the updates you submit to Play Store reflect after a day.
If you are worried about having a cross platform app, then you might want to try building a responsive web app which caters to almost any smartdevice.