Imagine the simple situation. You want to open an Android project in Android Studio.
Click File, Open. Find the project and click Ok.
Android Studio will open the project. Gradle seems to be working, but there is no Run or Debug action.
Android Studio does not provide any hint where is the issue.
The solution is simple. One important file is missing: settings.gradle. The file defines which modules should be included during the build.
To fix the issue just create settings.gradle in the root of your project:
include ':app'
Click Sync Gradle and within few moments you should be able to run the application.
If your application contains more modules, you can specify them in a similar way like in sdl2-android-example/settings.gradle.