试图重构这个Pomodoro Clock使用React Hooks。在单击“开始计时器”按钮时,倒计时没有启动时出现问题。我认为问题来自intervalRef。
我正确使用useRef吗?
https://codesandbox.io/s/k95zk32897
如果你不想去沙箱:
import React, {useState, useRef } from 'react'
export default function Pomodoro() {
const [seconds, setSeconds] = useState(0)
const [workMinutes, setWorkMinutes] = useState(25)
const [restMinutes, setRestMinutes] = useState(5)
const [start, setStart] = useState(false)
const [relax, setRelax] = useState(false)
// Control functions
const intervalRef = useRef();
function startTimer() {
if(!intervalRef.current){
intervalRef.current = setInterval(1000)
}
setStart(!start)
}
function pauseTimer() {
if(!intervalRef.current){
clearInterval(intervalRef.current)
intervalRef.current = undefined
}
}
function resetTimer() {
if(!intervalRef.current){
clearInterval(intervalRef.current)
intervalRef.current = undefined
}
setSeconds(0)
setWorkMinutes(25)
setRestMinutes(5)
setStart(false)
setRelax(false)
}
function timer() {
if(seconds === 0){
setSeconds(59)
}else{
setSeconds(seconds - 1)
}
if(relax) {
if(seconds === 0){
setRestMinutes(restMinutes - 1)
}
else if(restMinutes === 5){
setRestMinutes(4)
}else{
setRestMinutes(restMinutes)
}
}
if(restMinutes === -1) {
setRestMinutes(5)
setRelax(false)
} else {
setWorkMinutes( seconds === 0 ? workMinutes - 1 : workMinutes === 25 ? 24 : workMinutes)
if (workMinutes === -1) {
setWorkMinutes(25)
setRelax(true)
}
}
}
return (
<>
{timer}
<p>{relax ? 'Take a Break' : 'Get Busy'}</p>
<p>{relax ? restMinutes : workMinutes} : {seconds < 10 ? `0${seconds}` : seconds}</p>
<button onClick={start ? pauseTimer: startTimer}>{start ? 'Pause' : 'Start'}</button>
<button onClick={resetTimer}>Reset</button>
</>
)
}
你忘记了setInterval
的回调,但我宁愿这样做:
import React, { useState, useEffect } from "react";
export default function Pomodoro() {
const [seconds, setSeconds] = useState(25 * 60);
const [paused, setPaused] = useState(true);
useEffect(() => {
const int = setInterval(() => {
console.log(`${Date.now()} - paused: ${paused}`);
if (!paused) {
setSeconds(s => s - 1);
}
}, 1000);
return () => {
clearInterval(int);
};
}, [paused]);
function startTimer() {
setPaused(false);
}
function pauseTimer() {
setPaused(true);
}
function resetTimer() {
setPaused(true);
setSeconds(25 * 60);
}
return (
<>
{`${Math.floor(seconds / 60)}:${("00" + (seconds % 60)).slice(-2)}`}
<button onClick={paused ? startTimer : pauseTimer}>
{paused ? "Start" : "Pause"}
</button>
<button onClick={resetTimer}>Reset</button>
</>
);
}
沙箱:https://codesandbox.io/s/k9j70jrjy5
你真的不需要这么多状态 - 它们是相互依赖的,所以你可以简化逻辑(当然你可以再做一次工作/放松功能,我没有打扰)。
你可以通过10分钟而不是25分钟来处理这样的放松计时器:
function startRelaxTimer() {
setSeconds(10 * 60);
}
或者通过在其他状态下处理它然后你需要做两次(只有当你在切换时记住旧状态时才会好)。
const [relax, setRelax] = useState(false);
const [relaxSeconds, setRelaxSeconds] = useState(10 * 60);
useEffect(() => {
const int = setInterval(() => {
console.log(`${Date.now()} - paused: ${paused}`);
if (!paused) {
relax ? setRelaxSecdonds(s => s - 1) : setSeconds(s => s - 1);
}
}, 1000);
return () => {
clearInterval(int);
};
}, [paused, relax]);