Knowing Java and knowing Android are fairly different things. I'd sure consider something like RubyMotion ($) or React Native or Cordova or... anything unless

Knowing Java and knowing Android are fairly different things. I'd sure consider something like RubyMotion ($) or React Native or Cordova or... anything unless you specifically need functionality they don't offer or make onerous. There's nothing wrong with focusing on one platform then another, or get a lot of the way done with one then work on the other.