FlatList onEndReached被多次调用 [英] FlatList onEndReached being called multiple times

问题描述

我正在做一个本机反应项目，用户可以使用Flickr API搜索图像，其他所有工作都很好，但是实现分页时遇到了问题.我已经使用FlatList的onEndReached来检测用户何时滚动到列表的末尾，但是问题是onEndReached被多次调用(包括第一次渲染期间被调用).如此处所述，我什至禁用了弹跳功能，但仍被多次调用

I'm making a react native project where user can search images using Flickr API, Everything else is working fine but the problem i'm having while implementing pagination. I have used FlatList's onEndReached to detect when user has scrolled to the end on the list, but the problem is onEndReached is being called multiple times(including one during the first render). I have even disabled bounce as said here but it's still being called more than once

 export default class BrowserHome extends React.Component {
  constructor(props) {
    super(props);
    this.state = {
      isLoading: false,
      tagParam: "cat",
      pageNum: -1,
      data: [],
      photosObj: ""
    };
  }

  componentDidMount() {
    this.setState({
      isLoading: true
    });
    try {
      this.makeRequest();
    } catch {
      console.log("error has occurred");
    }
  }

  makeRequest = () => {
    const { tagParam, pageNum } = this.state;
    let url = `https://api.flickr.com/services/rest/? 
               method=flickr.photos.search
               &api_key=${apiKey}&format=json&tags=${tagParam}
               &per_page=30&page=${pageNum + 1}&nojsoncallback=1`;
    fetch(url, {
      method: "GET"
    })
      .then(response => response.json())
      .then(responseJSON => {
        this.setState({
          data: this.state.data.concat(responseJSON.photos.photo),
          isLoading: false,
          pageNum: responseJSON.photos.page
        });
      })
      .catch(error => {
        console.log(error);
        this.setState({ isLoading: false });
        throw error;
      });
  };

  render() {
    if (this.state.isLoading) {
      return <ActivityIndicator animating={true} size="large" />;
    }

    return (
      <View
        style={{
          flex: 1,
          height: 200,
          justifyContent: "flex-start",
          width: screenSize.width,
          backgroundColor: "black"
        }}
      >
        <Text>This is browserhome</Text>
        <FlatList
          style={{
            width: screenSize.width
          }}
          numColumns={3}
          data={this.state.data}
          keyExtractor={item => item.id}
          bounces={false}
          onEndReachedThreshold={1}
          onEndReached={({ distanceFromEnd }) => {
            this.loadMoreItem();
            alert("end reached call");
          }}
          renderItem={({ item, index }) => (
            <>
              <ImageTile imageURL={this.createImageURL(item)} />
            //  <Text style={{ color: "white" }}>
             //   {index}
             //   {console.log(index)}
             // </Text>
            </>
          )}
        />
      </View>
    );
  }

  createImageURL(item) {
    let server = item.server,
      id = item.id,
      secret = item.secret;
    let urlString = `https://farm${
      item.farm
    }.staticflickr.com/${server}/${id}_${secret}_s.jpg`;
    return urlString;
  }

  loadMoreItem() {
    this.makeRequest();
  }
}

推荐答案

此解决方案对我有用.在 FlatList 组件中添加 onMomentumScrollBegin 并修改 onEndReached .

This solution worked for me. Add onMomentumScrollBegin and modify onEndReached in FlatList Component.

<FlatList
style = { ...}
data = {data}
initialNumToRender = {10}
onEndReachedThreshold = {0.1}
onMomentumScrollBegin = {() => {this.onEndReachedCalledDuringMomentum = false;}}
onEndReached = {() => {
    if (!this.onEndReachedCalledDuringMomentum) {
      this.retrieveMore();    // LOAD MORE DATA
      this.onEndReachedCalledDuringMomentum = true;
    }
  }
}
/>

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