Implement pull to refresh FlatList

please help me out to implement pull to refresh on my app, I'm kinda new to react native, thanks. I don't know how to handle onRefresh and refreshing.

class HomeScreen extends Component {
  state = { refreshing: false }

  _renderItem = ({ item }) => <ImageGrid item={item} />

  _handleRefresh = () => {
   
  };

  render() {
    const { data } = this.props;
    if (data.loading) {
      return (
        <Root>
          <Loading size="large" />
        </Root>
      )
    }
 return (
   <Root>
     <HomeHeader />
     <FlatList
       contentContainerStyle={{ alignSelf: 'stretch' }}
       data={data.getPosts}
       keyExtractor={item => item._id}
       renderItem={this._renderItem}
       numColumns={3}
       refreshing={this.state.refreshing}
       onRefresh={this._handleRefresh}
     />
   </Root>
  );
 }
}

export default graphql(GET_POSTS_QUERY)(HomeScreen);

Set variable

this.state = { 
    isFetching: false,
}

Create Refresh function

onRefresh() {
    this.setState({isFetching: true,},() => {this.getApiData();});
}

And in last set onRefresh and refreshing in FlatList.

<FlatList
    data={ this.state.FlatListItems }
    onRefresh={() => this.onRefresh()}
    refreshing={this.state.isFetching}
/>

After fetching Data in function getApiData Make sure to set false isFetching.

this.setState({ isFetching: false })

You can also use refreshControl in Flatlist, ScrollView, and any other list component.

<FlatList
  contentContainerStyle={{ alignSelf: 'stretch' }}
  data={data.getPosts}
  keyExtractor={(item) => item._id}
  renderItem={this._renderItem}
  numColumns={3}
  refreshControl={
    <RefreshControl
      refreshing={this.state.refreshing}
      onRefresh={this._handleRefresh}
    />
  }
/>
    

// Sample code representing pull to refresh in flatlist. Modify accordingly.

import React, { Component } from 'react'
    import { Text, View,StyleSheet,FlatList,Dimensions,Image,TouchableHighlight } from 'react-native'
    
    export default class Home extends Component {
    
        constructor(props) 
        {
            super(props);
        this.state = {
            data : [],
            gender : "",
            isFetching: false,
        }
        }
    
    componentWillMount()
    {
    
        this.searchRandomUser()
    }
    
    onRefresh() {
        this.setState({ isFetching: true }, function() { this.searchRandomUser() });
     }
    
    searchRandomUser = async () =>
    {
       const RandomAPI = await fetch('https://randomuser.me/api/?results=20')
       const APIValue = await RandomAPI.json();
        const APIResults = APIValue.results
          console.log(APIResults[0].email);
          this.setState({
              data:APIResults,
              isFetching: false
          })
    
    }
    
      render() {
        return (
          <View style = {styles.container}>
     <TouchableHighlight
     onPressOut = {this.searchRandomUser}
         style = {{width:deviceWidth - 32, height:45,backgroundColor: 'green',justifyContent:"center",alignContent:"center"}}>
              <Text style = {{fontSize:22,color: 'white',fontWeight: 'bold',textAlign:"center"}}>Reload Data</Text>
         </TouchableHighlight>
     <FlatList
            data={this.state.data}
            onRefresh={() => this.onRefresh()}
          refreshing={this.state.isFetching}
            keyExtractor = { (item, index) => index.toString() }
            renderItem={({item}) =>
            <View style = {styles.ContainerView}>
            <View>
    <Image
    source={{uri : item.picture.large}}
    style = {{height:100,width:100,borderRadius: 50,marginLeft: 4}}
    resizeMode='contain'
    />
    </View>
    
    <View style = {{flexDirection: 'column',marginLeft:16,marginRight: 16,flexWrap:'wrap',alignSelf:"center",width: deviceWidth-160}}>
    <Text>Email Id : {item.email}</Text>
    
    <Text>Full Name : {this.state.gender} {item.name.first} {item.name.last}</Text>
    <Text>Date of birth : {item.dob.age}</Text>
    <Text>Phone number : {item.phone}</Text>
    
    </View>
    
    </View>
            }
            />
          </View>
        )
      }
    }
    const deviceWidth = Dimensions.get('window').width
    const deviceHeight = Dimensions.get('window').height
    const styles = StyleSheet.create({
        container: {
          flex: 1,
          alignItems: 'center',
          justifyContent: 'center',
          marginTop:22
        },
        ContainerView:
        {
            // backgroundColor:'grey',
            marginBottom:20,
            paddingVertical:10,
            backgroundColor: '#F5F5F5',
    
            borderBottomWidth:0.5,
            borderBottomColor:'grey',
            width: deviceWidth-40,
            marginLeft:20,
            marginRight:20,
            marginTop:20,
            flexDirection:'row'
        }
      });

const [refreshing, setRefreshing] = useState(false)
    
 <FlatList
     style={{ padding: 15 }}
     refreshControl={
         <RefreshControl 
             refreshing={refreshing} 
             onRefresh={_onRefresh}
             tintColor="#F8852D"/>
     }
     showsVerticalScrollIndicator={false}
     data={listData}
     renderItem={renderItem}
     item={(item, index) => index.toStirng()}
     onEndReachedThreshold={0.8}
     onEndReached={() => onEndReached()}
     ListFooterComponent={() => renderFooter()}
 /> 

> _onRefresh Function

const _onRefresh = () => {
    console.log('_onRefresh')
    setRefreshing(true);
    getPosts();
};

If someone is interested in doing it with React Hooks here is it:

First create isRefreshing state:

const [isRefreshing, setIsRefreshing] = useState(false)

Then create your onRefresh function that calls API to refresh data:

const onRefresh = () => {
    //set isRefreshing to true
    setIsRefreshing(true)
    callApiMethod()
    // and set isRefreshing to false at the end of your callApiMethod()
}

And after that, your FlatList component that looks like that:

return (
    <FlatList
        style={styles.flatList}
        onRefresh={onRefresh}
        refreshing={isRefreshing}
        data={data}
        renderItem={renderItem}
        keyExtractor={item => item.id.toString()}
    />
)

"Pull to refresh" concept implies that the list can be manually refreshed thus can be changed outside the current view (e.g. fetched from server). So the callback onRefresh has to trigger the data reloading process (e.g. send a request to the server) and set the refreshing variable to truthy value. This will notify the user that the process was started by showing loading indicator. Once you got the data ready you need to set refreshing to falsy so the view will hide loading indicator.

this is the best that I can do. my Code Image

when I pull it down it dosen't refetch data from server I'm running graphql server which connected by Apollo to the app, and I don't know how to get data from server in _getData() function.

Instead of using pull to refresh on flat-list simply use on Scroll View.

Set Refresh State

this.state = { 
     isFetching: false,
  }

Set onFresh in ScrollView

<ScrollView
  refreshControl={
    <RefreshControl
      refreshing={this.state.refresh}
      onRefresh={() => this.onRefresh()}
      tintColor="red"
    />
  }>
  <FlatList data={data} renderItem={this._renderItem} numColumns={3} />
</ScrollView>;

In OnRefreshFunction

  onRefresh() {
    this.setState({refresh: true});
    setTimeout(() => {
      this.setState({refresh: false});
    }, 2000);
  }

You can check the official document:

https://reactnative.dev/docs/refreshcontrol