there are several ways to import an existing IntelliJ Idea project into Eclipse. JetBrains offers an export to Eclipse for that purpose (see [1]). However, in case of Android Studio, it might be possible you'll need some manual tweaking of the project setup to be able to compile it properly. Check [2], [3], and [4].
After that you can can import the source code with UML Lab to create class diagrams (see [5]).
Note, if you just want to generate a UML Class Diagram for your source code, it's not necessary to have the code free of compile errors (though Round-Trip-Engineering NG benefits from a fully compilable source code, e.g. resolving of references works better).
Comments
there are several ways to import an existing IntelliJ Idea project into Eclipse. JetBrains offers an export to Eclipse for that purpose (see [1]). However, in case of Android Studio, it might be possible you'll need some manual tweaking of the project setup to be able to compile it properly. Check [2], [3], and [4].
After that you can can import the source code with UML Lab to create class diagrams (see [5]).
Note, if you just want to generate a UML Class Diagram for your source code, it's not necessary to have the code free of compile errors (though Round-Trip-Engineering NG benefits from a fully compilable source code, e.g. resolving of references works better).
Best regards,
Manuel
[1] https://www.jetbrains.com/idea/help/exporting-intellij-idea-projects-to-eclipse.html
[2] http://stackoverflow.com/questions/17481915/how-to-import-android-studio-project-in-eclipse
[3] http://stackoverflow.com/questions/16745793/how-do-you-open-an-android-studio-project-in-eclipse
[4] http://www.101apps.co.za/articles/importing-android-studio-projects-into-eclipse.html
[5] http://www.uml-lab.com/en/uml-lab/tutorials/reverse-engineering-tutorial/