Migrate to Kotlin #434
Description
As Kotlin seems to be the future of native Android programming, we may need to gradually migrate our codebase to Kotlin with best practices so there is less technical debt and also be welcoming to new contributors.
If you are familiar with Kotlin, please try to file issue and make pull requests to achieve this if you can. It is okay to make a PR with minor changes. Do not need to migrate entire codebase to Kotlin all at a time.