Android Studio Git Push Rejected

after push follow these,

VCS --> Git --> Branches

then select origin/master --> Rebase

after finish rebase successful message, you could able to push to remote directory. Hope this helps you.

As suggested in the comments you should pull the changes first, if you are working on a new repository that could happened when you create your remote repo with a readme or a licence file. To pull the changes from the user interface you should use, VCS > Git > Pull then select the master branch (depends)

after that you can Git > Push without problem.