React Native：按下 'like' 按钮时如何处理呈现的 FlatList 中每个项目的状态？

Question

我正在尝试为平面列表中的每个单独项目处理呈现的平面列表（从 Firebase 加载数据）中 'heart' 图标的状态。

代码有效，心形图标会填满，按下图标时数据会推送到数据库。同样，再次按下心形图标会恢复图标并从数据库中删除 'like'。

但是，当我尝试点击心形图标时，它会在列表中每个项目的心形图标的填充状态和空心状态之间切换更改该特定项目的状态。

我知道我需要在本地处理平面列表中每个项目的状态，但我不知道该怎么做。任何帮助，将不胜感激。代码如下：

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 对 json 回复中的所有项目都是正确的要更正它，您可以更新状态数组 json

 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

[{item},{item}]

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

然后获取按下的项目的索引

Answer 2

好的，问题是您有一个单一的 liked 状态值而不是数组。您应该首先将 liked 更改为一个数组（它将存储被喜欢的 post 的 id）。也许称它为更合适的名称，例如 likePosts。然后，您可以在喜欢或不喜欢时从数组中添加或删除 post 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>
    );
  }
}

React Native：按下 'like' 按钮时如何处理呈现的 FlatList 中每个项目的状态？

React Native: how to handle state for each item in a rendered FlatList when pressing the 'like' button?

setstate

react-native

react-native-flatlist