Flutter is an SDK to build cross-platform mobile apps Android Studio is an IDE focused on mobile app development

There is no "OR" option here. You can use Flutter and Android Studio both in a project - these 2 exist for different purposes and do not overlap, hence no competition.

As a fresher when you want to start Android developement you should have to learn first basic of android. Then you can go with Dart to learn CrosPlatform App developement with Flutter. Flutter is the future trending framwork to develope applications for web,Mobile, windows, mac... But Before start with Flutter You should have basics of Android app development with Android studio. If you want to develop ios App, should start basic developement with XCode.