Error: Unfortunately you can't have non-Gradle Java modules and > Android-Gradle modules in one project
Solution 1:
1- close the project
2- close Android Studio IDE
3- delete the .idea directory
4- delete all .iml files
5- open Android Studio IDE and import the project
Answer from here
Solution 2:
- Go to File -> Invalidate Caches/Restart.
- Close the project.
- Go to project folder and delete .idea folder.
- Delete YourProjectName.iml in project folder.
- Delete app.iml in app folder.
- Open Android studio -> open existing project, and then select your project.
- The Load Settings error and Unsupported modules detected error will be gone.