You won't find a gradle window view in flutter project, so here is a solution for that.. In command prompt navigate to bin folder of jdk and run this command
keytool -list -v -keystore "C:\Users\yourusernamehere\.android\debug.keystore" -alias androiddebugkey -storepass android -keypass android
change user name in path

You won't find a gradle window view in flutter project, so here is a solution for that.. In command prompt navigate to bin folder of jdk and run this command
keytool -list -v -keystore "C:\Users\yourus\.android\debug.keystore" -alias androiddebugkey -storepass android -keypass android
then you can copy sha from there