Refactoring all Java classes to Kotlin

[jeryini]

Hello @dji-dev @DJI-William !

We're using this UX-SDK and we have cloned the repository due to introducing some things specific to our needs. We've also refactored/moved some classes from Java to Kotlin due to less overhead when using some features such as sealed classes. We're now fetching your changes upstream and trying to incorporate them in our cloned repo. But it would be much easier if all classes in Java would also be converted to Kotlin in this repository. During our conversion, we did not notice any issues by doing simple conversion from Java to Kotlin class. Is there something we can help to make this repository use only Kotlin? For example, would you accept a PR that would contain the complete conversion?

[Michael-DJI]

@jeryini we could accept any PR which truelly refine the current code, but please create separate PR for reviewing, the first one could be about "introducing some things specific to our needs" the second one is about "refactored/moved some classes from Java to Kotlin"

[jeryini]

Hello @Michael-DJI

Great, nice to hear that you would consider accepting that kind of changes. Sure, the first PR would be only to convert existing Java classes to Kotlin.