推荐一款高性能React Native计时器组件：react-native-animated-stopwatch-timer

import React from 'react';
import { View, Text, StyleSheet } from 'react-native';
import StopwatchTimer from 'react-native-animated-stopwatch-timer';
 
export default class TimerExample extends React.Component {
  render() {
    return (
      <View style={styles.container}>
        <StopwatchTimer
          size={100}
          color="#000000"
          backgroundColor="#FFFFFF"
          seconds={0}
          hours={0}
          minutes={0}
          secondsIntervalInMillis={1000}
          onTick={(d) => console.log(d.hours + ':' + d.minutes + ':' + d.seconds)}
          onFinish={() => console.log('Timer finished!')}
          running={true}
          renderTitle={({hours, minutes, seconds}) => (
            <Text style={styles.title}>
              {hours}:{minutes}:{seconds}
            </Text>
          )}
        />
      </View>
    );
  }
}
 
const styles = StyleSheet.create({
  container: {
    flex: 1,
    justifyContent: 'center',
    alignItems: 'center',
  },
  title: {
    fontSize: 20,
    textAlign: 'center',
    margin: 10,
  },
});

这段代码演示了如何在React Native应用程序中使用react-native-animated-stopwatch-timer组件创建一个计时器。它包括计时器的基本设置，如颜色、大小和初始时间，以及如何自定义计时器的渲染和响应每一秒的变化。