Managing multiple setState() methods in single class? - flutter

Question

I am creating a timer when it will come to 0. It will navigate to the next Page.(Not created navigation yet). Till the timer is on user can answer the questions. The problem is I want to start the timer as the StartGame() file opens. In main.dart I have created a navigation for this on click on button. But when this page loads it automatically calls both ( in void getNum() and startTime() ) setState methods() one by one. Therefore answers (options) that I created as buttons automatically changes without onPressed by user. But I only want startTime() method to be called once as widget builds / inits. then after the getNum() method on every click of user.
How do i make these two setState() methods to be called individually without affecting each other.
class StartGame extends StatefulWidget {
StartGameState createState() => StartGameState();
}
class StartGameState extends State<StartGame> {
int no1, no2, no3, no4, inp1, inp2;
int pos;
int res;
List<int> answers;
GenerateQuestion g = new GenerateQuestion();
void getNum() {
answers = g.generateNum();
pos = g.answerPosition();
inp1 = g.generateValue();
inp2 = g.generateValue();
res = inp1 + inp2;
answers.add(res);
answers.shuffle();
setState(() {
no1 = answers[0];
no2 = answers[1];
no3 = answers[2];
no4 = answers[3];
print("set state 1 called");
});
} // void get Num ends here
//counter timer starts from herer
int counter = 10;
Timer timer;
void startTime() {
counter = 10;
timer = new Timer.periodic(Duration(seconds: 1), (timer) {
if (counter > 0) {
setState(() {
counter--;
print("set state 2 called");
});
} else {
timer.cancel();
}
});
}

Answer 1

You can achieve this using the initState() method, it gets only called once when the widget is built.
class _StartGameState extends State<StartGame> {
#override
void initState() {
startTime(); //this function only gets called once
super.initState();
}
//your Code...