MainActivity.java

package test.com.sessionm.app;
import test.com.sessionm.R;
import com.sessionm.api.BaseActivity;

//Just extend the BaseActivity class.
//This will automatically make lifecycle calls for you.
public class MainActivity extends BaseActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.app_activity);
        //continue with normal activity creation...
    }
    @Override
    public void onSessionStateChanged(SessionM sessionM, SessionM.State state) {
    }

    @Override
    public void onSessionFailed(SessionM sessionM, int i) {

    }

    @Override
    public void onUserUpdated(SessionM sessionM, User user) {
    }

    @Override
    public void onUnclaimedAchievement(SessionM sessionM, AchievementData achievementData) {
    }

    @Override
    public void onMessageUpdated(SessionM sessionM, MessageData messageData) {
    }
}

Which class is this MessageData?