My Android Studio project keeps running my old project/application

For me, 'Gradle -> Tasks -> other -> clean' worked.

I would make a copy of the project in a new folder and in this copy delete the following;

• .iml file
• .gradle folder
• .idea folder
• build folder

then open Android Studio and select 'File > Import Project...' and select the new projects settings.gradle file and click 'open'

You might have to check the dependencies and re-build but hopefully this should set things up in AS from scratch.