To designate the programming language used in 'Fastfile' within Android Studio, follow these steps:
- Open the 'Fastfile' file in Android Studio.
- Look for the file extension at the bottom-right corner of the screen. It should be '.rb' if the file is written in Ruby programming language.
- If the file extension is not '.rb', click on it and select 'Ruby' as the language from the dropdown menu.
- If the dropdown menu does not show 'Ruby' as an option, you may need to install the Ruby plugin in Android Studio first.
- To install the Ruby plugin, go to 'Preferences' (or 'Settings' on Windows) -> 'Plugins' -> search for 'Ruby' -> click on 'Install'.
- Once the Ruby plugin is installed, restart Android Studio and follow steps 1-3 again to designate 'Ruby' as the programming language for 'Fastfile'.