React Native：当按下“like”按钮时，如何为呈现的 FlatList 中的每个项目处理 state？

Question

我正在尝试为平面列表中的每个单独项目处理 state 在呈现的平面列表（从 Firebase 加载数据）中的“心”图标。

该代码有效，因为填充了心形图标，并在按下图标时将数据推送到数据库。 同样，再次按下心形图标将恢复图标并从数据库中删除“喜欢”。

但是，当单击心形图标时，它会在填充的 state 和空心 state 之间切换，用于列表中每个项目的心形图标，当我尝试更改特定项目的 Z9ED39E2EA931586B6A985A6942EF5 时

我知道我需要为 Flat List 中的每个项目在本地处理 state，但我不知道该怎么做。 任何帮助，将不胜感激。 下面的代码：

import React, {Component} from 'react';
import {
  FlatList,
  Text,
  View,
} from 'react-native';
import {Icon} from 'react-native-elements';
import {globalStyles} from '../config/Styles';
import Firebase from 'firebase';
import 'firebase/database';

export default class HomeScreen extends Component {
  constructor(props) {
    super(props);
    this.state = {
      //set value of postList variable as an empty array
      postList: [],
      liked: false,
    };
  }

  componentDidMount() {
    this.getPostData();
  }

  getPostData = () => {
    const ref = Firebase.database().ref('/posts');
    ref.on('value', snapshot => {
      const postsObject = snapshot.val();
      if (!postsObject) {
        console.log('NO DATA IN FIREBASE:', Date(Date.now()));
      } else {
        console.log('HOMESCREEN FIREBASE DATA RETRIEVED:', Date(Date.now()));
        const postsArray = Object.values(postsObject);
        this.setState({postList: postsArray});
      }
    });
  };

  render() {
    return (
      <View>
        <FlatList
          keyExtractor={post => post.id}
          data={this.state.postList}
          renderItem={({item: post}) => (
            <View style={globalStyles.postContainer}>
              <Text style={globalStyles.postText}>
                {post.heading}
                {'\n'}@{' '}
                <Text style={{fontWeight: 'bold'}}>{post.location}</Text>
                {'\n'}
                {post.description}
                {'\n'}
                listed by{' '}
                <Text style={{fontWeight: 'bold'}}>{post.createdBy}</Text>
                {'\n'}
                on <Text style={{fontWeight: 'bold'}}>{post.createdAt}</Text>
              </Text>
              <View style={globalStyles.iconMargin}>
                <Icon
                  raised
                  iconStyle={globalStyles.icon}
                  name={this.state.liked ? 'heart' : 'heart-o'}
                  size={28}
                  type="font-awesome"
                  onPress={() => {
                    const userKey = Firebase.auth().currentUser.uid;
                    const postKey = post.id;
                    const favRef = Firebase.database().ref(
                      'favourites/' + userKey + '/' + postKey,
                    );
                    if (this.state.liked === false) {
                      favRef.set({
                        id: postKey,
                        heading: post.heading,
                        description: post.description,
                        location: post.location,
                        createdAt: post.createdAt,
                        createdBy: post.createdBy,
                      });
                      this.setState({liked: true});
                    } else {
                      favRef.remove();
                      this.setState({liked: false});
                    }
                  }}
                />
                <Icon
                  raised
                  iconStyle={globalStyles.icon}
                  name="flag-o"
                  size={28}
                  type="font-awesome"
                  onPress={() =>
                    this.props.navigation.navigate('ReportPostScreen', post)
                  }
                />
              </View>
            </View>
          )}
        />
      </View>
    );
  }
}

Answer 1

因为 this.state.liked 将适用于 json 响应中的所有项目以更正它，您可以更新 stateFCA366 数组

 ItemPRessed =(index)=>{let dataArray = this.state.data
  dataArray[index].liked = !dataArray[index].liked
  this.setState({
    data:dataArray
  })}

而不是this.state.liked使用post.liked所以它将特定于项目而不是this.setState({liked: true}); 放

this.ItemPRessed(Index)

我不知道你的索引在你的 json 中是如何工作的，如果是这样的话

[{item},{item}]

那么你可以使用renderItem=({item: post, index})而不是renderItem={({item: post})

获取按下它的项目的索引

Answer 2

好的，问题是你有一个单一的liked state 值而不是数组。 您应该首先将liked的内容更改为一个数组（它将存储被喜欢的帖子的 ID）。 也许将其称为更合适的名称，例如likePosts 。 然后，您可以在喜欢或不喜欢它们时从数组中添加或删除帖子 ID（并在决定显示什么图标时检查likedPosts数组的值）。

您修改后的代码应如下所示：

import React, {Component} from 'react';
import {
  FlatList,
  Text,
  View,
} from 'react-native';
import {Icon} from 'react-native-elements';
import {globalStyles} from '../config/Styles';
import Firebase from 'firebase';
import 'firebase/database';

export default class HomeScreen extends Component {
  constructor(props) {
    super(props);
    this.state = {
      //set value of postList variable as an empty array
      postList: [],
      likedPosts: [],
    };
  }

  componentDidMount() {
    this.getPostData();
  }

  getPostData = () => {
    const ref = Firebase.database().ref('/posts');
    ref.on('value', snapshot => {
      const postsObject = snapshot.val();
      if (!postsObject) {
        console.log('NO DATA IN FIREBASE:', Date(Date.now()));
      } else {
        console.log('HOMESCREEN FIREBASE DATA RETRIEVED:', Date(Date.now()));
        const postsArray = Object.values(postsObject);
        this.setState({postList: postsArray});
      }
    });
  };

  render() {
    return (
      <View>
        <FlatList
          keyExtractor={post => post.id}
          data={this.state.postList}
          renderItem={({item: post}) => (
            <View style={globalStyles.postContainer}>
              <Text style={globalStyles.postText}>
                {post.heading}
                {'\n'}@{' '}
                <Text style={{fontWeight: 'bold'}}>{post.location}</Text>
                {'\n'}
                {post.description}
                {'\n'}
                listed by{' '}
                <Text style={{fontWeight: 'bold'}}>{post.createdBy}</Text>
                {'\n'}
                on <Text style={{fontWeight: 'bold'}}>{post.createdAt}</Text>
              </Text>
              <View style={globalStyles.iconMargin}>
                <Icon
                  raised
                  iconStyle={globalStyles.icon}
                  name={this.state.likedPosts.indexOf(post.id) > -1 ? 'heart' : 'heart-o'}
                  size={28}
                  type="font-awesome"
                  onPress={() => {
                    const userKey = Firebase.auth().currentUser.uid;
                    const postKey = post.id;
                    const favRef = Firebase.database().ref(
                      'favourites/' + userKey + '/' + postKey,
                    );

                    // This checks that the array doesn't contain the post id (i.e. the post was not previously liked)
                    if (this.state.likedPosts.indexOf(post.id) === -1) {
                      favRef.set({
                        id: postKey,
                        heading: post.heading,
                        description: post.description,
                        location: post.location,
                        createdAt: post.createdAt,
                        createdBy: post.createdBy,
                      });
                      // Include the post.id in the likedPosts array
                      this.setState({ likedPosts: [...this.state.likedPosts, post.id] })
                    } else {
                      favRef.remove();
                      // Remove the post.id from the likedPosts array
                      let index = this.state.likedPosts.indexOf(post.id);
                      this.setState({ likedPosts: this.state.likedPosts.splice(index, 1) })
                    }
                  }}
                />
                <Icon
                  raised
                  iconStyle={globalStyles.icon}
                  name="flag-o"
                  size={28}
                  type="font-awesome"
                  onPress={() =>
                    this.props.navigation.navigate('ReportPostScreen', post)
                  }
                />
              </View>
            </View>
          )}
        />
      </View>
    );
  }
}