react-native - Performance issue of flatList in react native

Question

I've tried flatlist but it has a bit of performance issues in android.

1. As I scroll down, it loads the list. But afterwards, it shows blank while scrolling upwards.

2. After reaching the end of the screen, it stops for a while and then loads the datas. Why is it not showing loader (activity indicator) at the bottom? Why is onEndReached and onEndReachedThreshold not working?

Plz have a look at the video here

https://youtu.be/5tkkEAUEAHM

My code:

import React, { Component } from 'react';
import {
  AppRegistry,
  StyleSheet,
  Text,
  View,
  FlatList,
  ActivityIndicator,
} from 'react-native';
import { List, ListItem, SearchBar } from "react-native-elements";

export default class FlatListExample extends Component
{
constructor(props) {
    super(props);

    this.state = {
      loading: false,
      data: [],
      page: 1,
      seed: 1,
      error: null,
      refreshing: false,
    };
  }

  componentDidMount() {
    this.makeRemoteRequest();
  }

  makeRemoteRequest = () => {
    const { page, seed } = this.state;
    const url = `https://randomuser.me/api/?seed=${seed}&page=${page}&results=20`;
    console.log('url', url);
    this.setState({ loading: true });

    setTimeout(()=>{
      fetch(url)
        .then(res => res.json())
        .then(res => {
          this.setState({
            data:  [...this.state.data, ...res.results],
            error: res.error || null,
            loading: false,
            refreshing: false
          });
        })
        .catch(error => {
          this.setState({ error, loading: false });
        });
    },0);

  };

  renderFooter = () => {
    if (!this.state.loading) return null;

    return (
      <View
        style={{
          paddingVertical: 20,
          borderTopWidth: 1,
          borderColor: "#CED0CE"
        }}
      >
        <ActivityIndicator animating size="large" />
      </View>
    );
  };

handleLoadMore = () =>{
  this.setState({
    page:this.state.page + 1,
  },()=>{
    this.makeRemoteRequest();
  })
}
  render() {
    return (
      <FlatList
        data={this.state.data}
        renderItem={({ item }) => (
          <ListItem
            roundAvatar
            title={`${item.name.first} ${item.name.last}`}
            subtitle={item.email}
            avatar={{ uri: item.picture.thumbnail }}
          />
        )}
        keyExtractor={item => item.email}
        ListFooterComponent={this.renderFooter}
        onEndReached={this.handleLoadMore}
        onEndReachedThreshold={50}
      />
    );
  }
}

AppRegistry.registerComponent('FlatListExample', () => FlatListExample);

Answer 1

我注意到你没有设置initialNumToRender. 从文档：

initialNumToRender：数字

在初始批次中渲染多少项目。这应该足以填满屏幕，但仅此而已。请注意，这些项目永远不会作为窗口渲染的一部分卸载，以提高滚动到顶部操作的感知性能。

因此，您需要估计在任何给定时间您希望看到多少个单元格并将其设置为该值。如果您还没有更新到最新的 react-native，我还建议您更新，其中包括对 FlatList 组件的各种改进。