How to use a button in a while loop in Arduino? - arduino

Question

So i tried to make a little quiz, it can use a lot of improvement but i would like to have a finished project before i better it. I want the user to choose the answer by pressing a button.
My code currently looks like this.
char serialData;
int i = 1;
int redLed = 12;
int greenLed=13;
int buttonA=11;
int buttonB=10;
int buttonC=9;
int lastState = LOW;
int currentState;
void setup()
{
Serial.begin(9600);
pinMode(redLed, OUTPUT);
pinMode(greenLed, OUTPUT);
pinMode(buttonA,INPUT);
pinMode(buttonB,INPUT);
pinMode(buttonC,INPUT);
// read the state of the switch/button:
currentState = digitalRead(buttonA);
if(lastState == HIGH && currentState == LOW)
Serial.println("A");
// save the the last state
lastState = currentState;
delay(100);
}
void loop()
{
vraag1();
delay(1000);
vraag2();
delay(1000);
vraag3();
delay(1000);
vraag4();
delay(1000);
vraag5();
delay(1000);
vraag6();
}
void vraag1()
{ //1
Serial.println(" 3+3=? ");
delay(400);
Serial.println(" A) 6");
delay(200);
Serial.println(" B) 5 ");
delay(200);
Serial.println(" C) 4 ");
delay(200);
while (Serial.available() ==0){} //2-2
/*
This is the part I added to resolve the issue - but it
does not work.
*/
currentState = digitalRead(buttonA);
if(lastState == HIGH && currentState == LOW)
Serial.println("A");
lastState = currentState;
if (Serial.available())
{ //3
serialData = Serial.read();
if (serialData == '6' || serialData == 'a' || serialData == 'A')
{ //4
Serial.println(" Correct ");
i++;
digitalWrite(greenLed, HIGH);
} //4
else
{ //5
Serial.println(" Incorrect ");
digitalWrite(redLed, HIGH);
} //5
}
delay(1000);
digitalWrite(redLed, LOW);
digitalWrite(greenLed, LOW);
}
This is the code I added to try it but it doesn't work at all. Does anyone have another suggestion?
currentState = digitalRead(buttonA);
if(lastState == HIGH && currentState == LOW)
Serial.println("A");
lastState = currentState;