Kotlin Not Working On Android Studio

All kotlin files can't be displayed on my Android Studio. Even when you directly convert java files into koltin, you can edit it, but it doesn't appear on the project file tree. A

Solution 1:

Please make sure that the .kt extension is associated with the Kotlin files in Settings | Editor | File Types.

Also note that the reason why "Kotlin Extensions for Android (obsolete)" has the "obsolete" word in its name is specifically to let you know that you should not install that plugin.