When cycling through options in a list the only items displayed is the last option (displayed twice)-CodePudding

I am trying to cycle through options in a list using left and right buttons that call the functions cycleLeft() and cycleRight(), but instead all I get is the second to last option displayed twice in a row and then the last option displayed once. this is for a react native app inside the main app function. any help is appreciated.

var gamesList = ["Quadratic", "Magic Square", "Settings", "Option 3"];
var index = 0;
var game = gamesList[index];

const [gameText, setGameText] = useState(gamesList[index]);
const [gameGame, setGameGame] = useState(gamesList[index]);
const zAnim = useRef(new Animated.ValueXY({ x: 0, y: 1000 })).current;

const cycleLeft  = () =>  {
  index = index - 1;
  if (index < 0) { index = gamesList.length - 1; };
  game = gamesList[index];
  setGameText(gamesList[index]);
  console.log(game   " "   index);
}

const cycleRight = () => {
  index = index   1;
  if (index > gamesList.length - 1) { index = 0; };
  game = gamesList[index];
  setGameText(gamesList[index]);
  console.log(game   " "   index);
}

CodePudding user response：

index should be stateful instead of gameText

var gamesList = ["Quadratic", "Magic Square", "Settings", "Option 3"];
const [index, setIndex] = useState(0);

const cycleLeft  = () =>  {
  setIndex(prevIndex => prevIndex - 1 < 0 ? gamesList.length - 1 : prevIndex - 1);
}

const cycleRight = () => {
  setIndex(prevIndex => prevIndex   1 > gamesList.length - 1 ? 0 : prevIndex   1);
}

//just for logging
useEffect(() => {
  console.log(gamesList[index]  " "   index);
}, [index]);

Wherever you were using gameText, you can just use gamesList[index] instead.