如何避免在 Flatlist 中重新渲染？

Question

我有一个来自 react-native 文档的 Flatlist 的简单示例 - https://snack.expo.dev/OQvPkym3t ，这是否正常，只有 15 个项目但是有 25 个渲染项目，您可以使用 console.log 查看？如何避免这种重新渲染？我可以在 renderItem 中使用 memoization 来防止重新渲染吗？

import React from 'react';
import { SafeAreaView, View, FlatList, StyleSheet, Text, StatusBar } from 'react-native';

const DATA = [
  {
    id: 'bd7acbea-c1b1-46c2-aed5-3ad53abb28ba',
    title: 'First Item',
  },
  {
    id: '3ac68afc-c605-48d3-a4f8-fbd91aa97f63',
    title: 'Second Item',
  },
  {
    id: '58694a0f-3da1-471f-bd96-145571e29d72',
    title: 'Third Item',
  },
    {
    id: 'bd7acbea-c1b1-46c2-aed5-3ad53abb28ba',
    title: 'First Item',
  },
  {
    id: '3ac68afc-c605-48d3-a4f8-fbd91aa97f63',
    title: 'Second Item',
  },
  {
    id: '58694a0f-3da1-471f-bd96-145571e29d72',
    title: 'Third Item',
  },
    {
    id: 'bd7acbea-c1b1-46c2-aed5-3ad53abb28ba',
    title: 'First Item',
  },
  {
    id: '3ac68afc-c605-48d3-a4f8-fbd91aa97f63',
    title: 'Second Item',
  },
  {
    id: '58694a0f-3da1-471f-bd96-145571e29d72',
    title: 'Third Item',
  },
    {
    id: 'bd7acbea-c1b1-46c2-aed5-3ad53abb28ba',
    title: 'First Item',
  },
  {
    id: '3ac68afc-c605-48d3-a4f8-fbd91aa97f63',
    title: 'Second Item',
  },
  {
    id: '58694a0f-3da1-471f-bd96-145571e29d72',
    title: 'Third Item',
  },
    {
    id: 'bd7acbea-c1b1-46c2-aed5-3ad53abb28ba',
    title: 'First Item',
  },
  {
    id: '3ac68afc-c605-48d3-a4f8-fbd91aa97f63',
    title: 'Second Item',
  },
  {
    id: '58694a0f-3da1-471f-bd96-145571e29d72',
    title: 'Third Item',
  },
];

const Item = ({ title }) => { 
  console.log('render')
  return (
  <View style={styles.item}>
    <Text style={styles.title}>{title}</Text>
  </View>
  )
};


const App = () => {
  const renderItem = ({ item }) => (
    <Item title={item.title} />
  );

  return (
    <SafeAreaView style={styles.container}>
      <FlatList
        data={DATA}
        renderItem={renderItem}
        keyExtractor={item => item.id}
      />
    </SafeAreaView>
  );
}

const styles = StyleSheet.create({
  container: {
    flex: 1,
    marginTop: StatusBar.currentHeight || 0,
  },
  item: {
    backgroundColor: '#f9c2ff',
    padding: 20,
    marginVertical: 8,
    marginHorizontal: 16,
  },
  title: {
    fontSize: 32,
  },
});

export default App;

Answer 1

您可以使用记忆来优化渲染。例如，您可以在提取项目的地方使用 useCallback，并使用自定义深度比较来进一步优化渲染。

你可以在我优化这段代码的地方查看这个小吃：https://snack.expo.dev/@amitdutta121/flatlist-simple

import React,{useCallback} from 'react';
import { SafeAreaView, View, FlatList, StyleSheet, Text, StatusBar } from 'react-native';

const DATA = [
  {
    id: 'bd7acbea-c1b1-46c2-aed5-3ad53abb28ba',
    title: 'First Item',
  },
  {
    id: '3ac68afc-c605-48d3-a4f8-fbd91aa97f63',
    title: 'Second Item',
  },
  {
    id: '58694a0f-3da1-471f-bd96-145571e29d72',
    title: 'Third Item',
  },
    {
    id: 'bd7acbea-c1b1-46c2-aed5-3ad53abb28ba',
    title: 'First Item',
  },
  {
    id: '3ac68afc-c605-48d3-a4f8-fbd91aa97f63',
    title: 'Second Item',
  },
  {
    id: '58694a0f-3da1-471f-bd96-145571e29d72',
    title: 'Third Item',
  },
    {
    id: 'bd7acbea-c1b1-46c2-aed5-3ad53abb28ba',
    title: 'First Item',
  },
  {
    id: '3ac68afc-c605-48d3-a4f8-fbd91aa97f63',
    title: 'Second Item',
  },
  {
    id: '58694a0f-3da1-471f-bd96-145571e29d72',
    title: 'Third Item',
  },
    {
    id: 'bd7acbea-c1b1-46c2-aed5-3ad53abb28ba',
    title: 'First Item',
  },
  {
    id: '3ac68afc-c605-48d3-a4f8-fbd91aa97f63',
    title: 'Second Item',
  },
  {
    id: '58694a0f-3da1-471f-bd96-145571e29d72',
    title: 'Third Item',
  },
    {
    id: 'bd7acbea-c1b1-46c2-aed5-3ad53abb28ba',
    title: 'First Item',
  },
  {
    id: '3ac68afc-c605-48d3-a4f8-fbd91aa97f63',
    title: 'Second Item',
  },
  {
    id: '58694a0f-3da1-471f-bd96-145571e29d72',
    title: 'Third Item',
  },
];


function propsAreEqual(prevprops, nextProps) {
  return JSON.stringify(prevprops) === JSON.stringify(nextProps)
}

const Item = React.memo(({ title }) => { 
  console.log('render')
  return (
  <View style={styles.item}>
    <Text style={styles.title}>{title}</Text>
  </View>
  )
},propsAreEqual);



const App = () => {
  
  const keyExtractor = useCallback((item)=>{item => item.id},[])

  
  const renderItem = ({ item }) => (
    <Item title={item.title} />
  );

  return (
    <SafeAreaView style={styles.container}>
      <FlatList
        data={DATA}
        renderItem={renderItem}
        keyExtractor={keyExtractor}
      />
    </SafeAreaView>
  );
}

const styles = StyleSheet.create({
  container: {
    flex: 1,
    marginTop: StatusBar.currentHeight || 0,
  },
  item: {
    backgroundColor: '#f9c2ff',
    padding: 20,
    marginVertical: 8,
    marginHorizontal: 16,
  },
  title: {
    fontSize: 32,
  },
});

export default App;

如何避免在 Flatlist 中重新渲染？

How to avoid rerender in Flatlist?

reactjs

react-native

react-native-flatlist