Cross-Platform Development Summary
You need to run your app on Android and on other major platforms, and don't wish to rewrite it from scratch for each one.
There is no single, simple solution to cross-platform development for all developers for all time.
The road you choose will be determined by the map you have and the ground in front of you. The latter is always changing, so the former should as well. The following is some notes I have collected on some of the major cross-platform approaches.