react native基于FlatList下拉刷新上拉加载实现代码示例

react native 的上拉加载一直困扰着自己，一直用的第三方组件，但是可维护性不高，而且也不太好用，最近工作没那么忙，就研究下了官方的FlatList，做出来的成果，比第三方组件流畅度高好多，而且也很好用

官方介绍：https://reactnative.cn/docs/flatlist/

下面是效果图：

ios效果图

android效果图

总体思路就是：就是计算屏幕高度，然后减去导航的头部，根据列表高度计算出每页的个数,然后向上取整。这样做的目的是：防止不满屏状态下的，onEndReached函数的主动触发。

方法实现：

 //满屏页面判断
 fullScreenJusting(ItemHeight) {
  const screnHeight = screnInfo.size.height;   //屏幕高度
  //计算列表个数
  const listNum = (screnHeight - 40) / ItemHeight;
  return Math.ceil(listNum);
 }

下拉刷新用的是 RefreshControl

官网地址：https://reactnative.cn/docs/refreshcontrol/#progressbackgroundcolor

具体代码：

import React, { Component } from 'react';
import {
 View,
 Text,
 Image,
 StyleSheet,
 FlatList,
 RefreshControl,
 ActivityIndicator,
} from 'react-native';
import { SafeAreaView } from 'react-navigation';
import screnInfo from '../utils/View';
import BaseStyle from '../constants/Style';
import { QUESTION_LIST } from '../constants/Api';
import { form_req } from '../utils/Request';

export default class TestScreen extends Component {
 constructor(props) {
  super(props);
  this.state = {
   data: [
   ],
   refreshing: false,
   fresh: true,
   animating: true,
   nomore: false,
   pageSize: 0,
   pageNumber: 1,
  };
 }
 componentDidMount() { //初始化的时候要判断长度 控制上拉加载

  const ListNums = this.fullScreenJusting(50);
  this.setState({
   pageSize: ListNums
  })
  this.onEndReachedCalled = false;
   this.getOrderList(ListNums, 1, true);

 }
 //满屏页面判断
 fullScreenJusting(ItemHeight) {
  const screnHeight = screnInfo.size.height;   //屏幕高度
  //计算列表个数
  const listNum = (screnHeight - 40) / ItemHeight;
  return Math.ceil(listNum);
 }

 getOrderList(ListNums, pageNumber, fresh) {
  let nomore;
  form_req(QUESTION_LIST, {
   page: pageNumber,
   perpage: ListNums,
  }).then(res => {
   if (res.code == 200) {
    const item = res.data;
    if (item.length < ListNums) {
     nomore = true
    } else {
     nomore = false
    }
    if (fresh) {
     this.setState({
      data: item,
      nomore: nomore
     })
     
    } else {
     this.setState({
      data: this.state.data.concat(item),
      nomore: nomore,
     })
    }
    // this.onEndReachedCalledDuringMomentum = true;

   } else {

   }
  });
 }

 renderItem = item => {
  return (
   
    {item.name}
   
  );
 };
 //列表线
 ItemSeparatorComponent = () => {
  return ;
 };
 //头部
 ListHeaderComponent = () => { };
 //尾部
 ListFooterComponent = () => {
  return (
   
    {
     this.state.data.length != 0 ?
      this.state.nomore ? (
       - 我是有底线的 -
      ) : (
        
         
         加载更多...
        
       )
      :
      null
    }

   
  );
 };
 //为空时
 ListEmptyComponent() {
  return (
   
    {/*  */}
    暂无订单
   
  );
 }
 _keyExtractor = (item,index) => item.id;

 _onEndReached = () => {
  if (!this.state.nomore && this.onEndReachedCalled ) {
   this.getOrderList(this.state.pageSize, ++this.state.pageNumber, false);
  }
  this.onEndReachedCalled=true;

 };
 _onRefresh() {
  this.setState({ nomore: false, pageNumber: 1 }, () => {
   this.getOrderList(this.state.pageSize, 1, true);
  })

 }

 render() {
  return (
   
    
      this.renderItem(item)}
      ItemSeparatorComponent={this.ItemSeparatorComponent}
      ListEmptyComponent={this.ListEmptyComponent}
      ListFooterComponent={this.ListFooterComponent}
      onEndReachedThreshold={0.1}
      refreshControl={
        {
         this._onRefresh();
        }}
       />
      }
     />
    
   
  );
 }
}

const styles = StyleSheet.create({
 listConten: {
  flex: 1,
  backgroundColor: '#ffffff',
 },
 item: {
  flexDirection: 'row',
  justifyContent: 'center',
  alignItems: "center",
  backgroundColor: '#ffffff',
  height: 50,
 },
 baseLine: {
  width: screnInfo.size.width,
  height: 1,
  backgroundColor: '#eeeeee',
 },
 noListView: {
  width: screnInfo.size.width,
  height: screnInfo.size.height - 140,
  justifyContent: 'center',
  alignItems: 'center',
 },
 NoListText: {
  marginTop: 15,
  fontSize: 18,
  color: '#999999',
 },
 noListImage: {
  width: 130,
  height: 140,
 },
 bottomfoot: {
  flexDirection: 'row',
  justifyContent: 'center',
  alignItems: 'center',
  padding: 10,
 },
 footText: {
  marginTop: 5,
  fontSize: 12,
  color: '#999999',
 },

 activeLoad: {
  flexDirection: 'row',
  justifyContent: 'center',
  alignItems: 'center',
 },
 ml: {
  marginLeft: 10,
 },
});

这里的坑就是：当初始化进来页面的时候 上拉会主动触发，所以这里加了一个开关 this.onEndReachedCalled = false； 初始化给一个false 当触发了 设为true,放在调取接口之后

代码都很简单易懂~ 有什么不懂的，或者有什么问题请留言，希望对大家的学习有所帮助，也希望大家多多支持脚本之家。