从流音频函数更新 useState 时无限重新渲染

Question

我正在构建一个应用程序 React Native，我将音频文件数组发送到 Expo AV Audio.Sound 对象中，加载它们，播放它们，然后尝试使用有关正在播放的音频文件的信息更新应用程序本身的显示(特别是用户在文件中的距离(。我正在尝试通过 useState 钩子更新显示，该钩子由音频播放器的回调函数调用。

我遇到的问题是，每当我尝试从音频播放器回调函数更改状态时，我都会陷入无限的重新渲染。简化代码如下：

import React, { useState} from 'react';
import { Audio } from 'expo-av';
const AudioPlayer = ({ user }) => {
const [currentProgress, setCurrentProgress] = useState(0);
const soundObject = new Audio.Sound();
soundObject.setOnPlaybackStatusUpdate(playbackUpdate);
// sets a function that is called every 500 milliseconds as the audio is played 
if(user) {
soundObject.loadAsync({user.message.path});
}
const play = () => {
soundObject.playAsync();
}
const playbackUpdate = (playbackObject) => {
setCurrentProgress(playbackObject.currentMillis);
// updating state with progress through audio file in milliseconds
}
return (
<View>
<Text>{currentProgress}</Text>
<Button title="play" onPress={play} />
</View>
)
}
export default AudioPlayer

Answer 1

请记住，函数体中的所有内容都将在每个渲染上运行 - 因此在本例中，您将创建一个新soundObject，并可能在每次渲染上运行soundObject.loadAsync调用。您需要利用其他钩子来避免这种情况 - 在您的情况下可能是useRef和useEffect。我建议通过钩子 api 参考来熟悉这些：https://reactjs.org/docs/hooks-reference.html

以下是我如何避免不必要的影响的快速尝试。您可能需要查看和调整依赖项数组，具体取决于您希望事情如何运行以及何时希望重新运行各种效果。例如，我不确定您是否需要重新创建Sound对象。

import React, { useState, useRef, useCallback, useEffect} from 'react';
import { Audio } from 'expo-av';
import { Button, View, Text } from 'react-native';
const AudioPlayer = ({ user }) => {
const [currentProgress, setCurrentProgress] = useState(0);
const soundObjectRef = useRef(new Audio.Sound());
useEffect(() => {
const playbackUpdate = (playbackObject) => {
setCurrentProgress(playbackObject.currentMillis);
// updating state with progress through audio file in milliseconds
}
soundObjectRef.current.setOnPlaybackStatusUpdate(playbackUpdate);
}, []); // do this only once per component mount
// sets a function that is called every 500 milliseconds as the audio is played 
useEffect(() => {
if (user) {
soundObjectRef.current.loadAsync({user.message.path});
}
}, [user]); // run this anytime user changes but do not run again if user doesn't change
const play = () => {
soundObjectRef.current.playAsync();
}
return (
<View>
<Text>{currentProgress}</Text>
<Button title="play" onPress={play} />
</View>
)
}
export default AudioPlayer