Getting skipped frames with RxAndroid on a simple call - rx-java2

Question

I'm implementing in a LauncherActivity (with just a loading indicator) an Observable (Single) from RxJava library to login with the previously recorded users credentials.
The activity is very very simple, and yet I get a skipped frames warning (40ish), both on my phone and on emulator, and I can't figure out why (though sometimes it doesn't show up).
Here is the code :
public class LauncherActivity extends AppCompatActivity {
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_launcher);
mProgressBar = findViewById(R.id.progress_bar);
mProgressBar.setVisibility(View.VISIBLE);
if (UsersUtils.hasCredentialsRecorded(this)) {
getAccessToken();
} else {
login();
}
}
public void getAccessToken() {
Callable<Token> callable = new Callable<Token>() {
#Override
public Token call() throws Exception {
final Map<String, byte[]> credentials = UsersUtils.getCredentials(getApplicationContext());
Token token = OauthCalls.getToken(new String(credentials.get(UsersUtils.PREFERENCES_USER_KEY)),
new String(credentials.get(UsersUtils.PREFERENCES_PASS_KEY)));
return token;
}
};
Single.fromCallable(callable)
.subscribeOn(Schedulers.io())
.subscribe(new DisposableSingleObserver<Token>() {
#Override
public void onSuccess(Token token) {
if (token == null) {
login();
} else {
Intent intent = new Intent(getApplicationContext(), MainActivity.class);
startActivity(intent);
}
}
#Override
public void onError(Throwable e) {
login();
}
});
}
public void login() {
Intent intent = new Intent(this, LoginActivity.class);
startActivity(intent);
}
}
Thanks a lot for your help !