React Native stopwatch implementation slow on iOS

Question

I have the following stopwatch implementation

import { useState, useEffect } from 'react';
import { Text, View, StyleSheet, Button } from 'react-native';

function TimerComponent() {
  const [isActive, setIsActive] = useState(false);
  const [time, setTime] = useState(0);

  useEffect(() => {
    let interval = null;

    if (isActive) {
      interval = setInterval(() => {
        setTime(time => time + 0.1);
      }, 100);
    } else {
      clearInterval(interval);
    }
    return () => {
      clearInterval(interval);
    };
  }, [isActive]);

  const handleStart = () => {
    setIsActive(true);
  };

  const handleReset = () => {
    setIsActive(false);
    setTime(0);
  };

  const roundedTime = time.toFixed(1);

  return (
    <View style={styles.outerContainer}>
      <Button
        title="Start"
        onPress={handleStart}
      />
      <Text style={styles.text}>{roundedTime}</Text>
      <Button
        title="Stop"
        onPress={handleReset}
      />
    </View>
  );
}

export default TimerComponent;

on Android it works as expected, when I compare to another stopwatch it reaches 30 seconds at the same time, but when I test on iOS it takes around 5 seconds longer.

Michael Bahl · Accepted Answer · 2024-04-01 08:25:54Z

1

Don‘t use setTime(time => time + 0.1); to calculate the passed time. Rather use Date:

const start = Date.now();

console.log('starting timer...');
// Expected output: "starting timer..."

setTimeout(() => {
  const millis = Date.now() - start;

  console.log(`seconds elapsed = ${Math.floor(millis / 1000)}`);
  // Expected output: "seconds elapsed = 2"
}, 2000);

answered Apr 1, 2024 at 8:25

Michael Bahl

3,7071 gold badge15 silver badges20 bronze badges

Sign up to request clarification or add additional context in comments.

Collectives™ on Stack Overflow

React Native stopwatch implementation slow on iOS

1 Answer 1

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

Comments

Your Answer

Sign up or log in

Post as a guest

Related