问题
Unsupported Modules Detected: Compilation is not supported for the following modules: MemorandamApp. Unfortunately, you can't have non-Gradle Java modules and Android-Gradle modules in one project.
This Error caused to erase my files. Newly opened files are affected by this problem.
回答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
The answer is taken from HERE
回答2:
Switch to project mode and go to .idea/modules.xml & delete the invalid/not existing path . Then File => Invalidate Caches / Restart.
来源：https://stackoverflow.com/questions/56035306/unsupported-modules-detected-unfortunately-you-cant-have-non-gradle-java-modul