Create a Firebase project
If you’re releasing your Flutter app on both iOS and Android, register both the iOS and Android versions of your app with the same Firebase project.
Register your app with Firebase
Make sure that you enter the ID that your app is actually using. You cannot add or modify this value after you register your app with your Firebase project. Both applicationId should be matched.
- Click Register app.
- Click Download google-services.json to obtain your Firebase Android config file (google-services.json).
- Move your config file into the android/app directory of your Flutter app.