react-native - 突出显示 React-Native FlatList 中的选定项目

Question

我组合了一个简单的 React-native 应用程序来从远程服务获取数据，并将其加载到 FlatList 中。当用户点击一个项目时，它应该被突出显示并保留选择。我相信这样一个微不足道的操作应该不难。我不确定我错过了什么。

import React, { Component } from 'react';
import {
  StyleSheet,
  Text,
  View,
  FlatList,
  ActivityIndicator,
  Image,
  TouchableOpacity,
} from 'react-native';

export default class BasicFlatList extends Component {
  constructor(props) {
    super(props);

    this.state = {
      loading: false,
      data: [],
      page: 1,
      seed: 1,
      error: null,
      refreshing: false,
      selectedItem:'null',
    };
  }

  componentDidMount() {
    this.makeRemoteRequest();
  }

  makeRemoteRequest = () => {
    const {page, seed} = this.state;
    const url = `https://randomuser.me/api/?seed=${seed}&page=${page}&results=20`;
    this.setState({loading: true});
    fetch(url)
      .then(res => res.json())
      .then(res => {
        this.setState({
          data: page === 1 ? res.results : [...this.state.data, ...res.results],
          error: res.error || null,
          loading: false,
          refreshing: false
        });
      })
      .catch(error => {
        this.setState({error, loading: false});
      });
  };

  onPressAction = (rowItem) => {
    console.log('ListItem was selected');
    console.dir(rowItem);
    this.setState({
      selectedItem: rowItem.id.value
    });
  }

  renderRow = (item) => {
    const isSelectedUser = this.state.selectedItem === item.id.value;
    console.log(`Rendered item - ${item.id.value} for ${isSelectedUser}`);
    const viewStyle = isSelectedUser ? styles.selectedButton : styles.normalButton;
    return(
        <TouchableOpacity style={viewStyle} onPress={() => this.onPressAction(item)} underlayColor='#dddddd'>
          <View style={styles.listItemContainer}>
            <View>
              <Image source={{ uri: item.picture.large}} style={styles.photo} />
            </View>
            <View style={{flexDirection: 'column'}}>
              <View style={{flexDirection: 'row', alignItems: 'flex-start',}}>
                {isSelectedUser ?
                  <Text style={styles.selectedText}>{item.name.first} {item.name.last}</Text>
                  : <Text style={styles.text}>{item.name.first} {item.name.last}</Text>
                }
              </View>
              <View style={{flexDirection: 'row', alignItems: 'flex-start',}}>
                <Text style={styles.text}>{item.email}</Text>
              </View>
            </View>
          </View>
        </TouchableOpacity>
    );
  }

  render() {
    return(
      <FlatList style={styles.container}
        data={this.state.data}
        renderItem={({ item }) => (
          this.renderRow(item)
        )}
      />
    );
  }
}

const styles = StyleSheet.create({
  container: {
    flex: 1,
    marginTop: 50,
  },
  selectedButton: {
    backgroundColor: 'lightgray',
  },
  normalButton: {
    backgroundColor: 'white',
  },
  listItemContainer: {
    flex: 1,
    padding: 12,
    flexDirection: 'row',
    alignItems: 'flex-start',
  },
  text: {
    marginLeft: 12,
    fontSize: 16,
  },
  selectedText: {
    marginLeft: 12,
    fontSize: 20,
  },
  photo: {
    height: 40,
    width: 40,
    borderRadius: 20,
  },
});

当用户点击列表中的一个项目时，“onPress”方法被调用，其中包含所选项目的信息。但是下一步在 Flatlist 中突出显示项目不会发生。 'UnderlayColor' 也没有帮助。
任何帮助/建议将不胜感激。

Answer 1

代替 this.state.selectedItem并设置/检查 rowItem.id.value ，我建议使用带有键值对的 Map 对象，如 RN FlatList 文档示例所示:https://facebook.github.io/react-native/docs/flatlist.html .也看看 js Map 文档:https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Map .

@j.I-V 推荐的 extraData Prop 将确保在 this.state.selected 更改选择时发生重新渲染。

您的 onPressAction 显然会与下面的示例有所不同，具体取决于您是要限制任何给定时间的选择数量还是不允许用户切换选择等。

此外，虽然不是必需的，但我喜欢为 renderItem 使用另一个类或纯组件。成分;最终看起来像下面这样:

export default class BasicFlatList extends Component {
  state = {
    otherStateStuff: ...,
    selected: (new Map(): Map<string, boolean>) //iterable object with string:boolean key:value pairs
  }

  onPressAction = (key: string) => {
    this.setState((state) => {
      //create new Map object, maintaining state immutability
      const selected = new Map(state.selected);
      //remove key if selected, add key if not selected
      this.state.selected.has(key) ? selected.delete(key, !selected.get(key)) : selected.set(key, !selected.get(key));
      return {selected};
    });
  }

  renderRow = (item) => {
    return (
        <RowItem
          {...otherProps}
          item={item}
          onPressItem={this.onPressAction}
          selected={!!this.state.selected.get(item.key)} />
    );
  }

  render() {
    return(
      <FlatList style={styles.container}
        data={this.state.data}
        renderItem={({ item }) => (
          this.renderRow(item)
        )}
        extraData={this.state}
      />
    );
  }
}


class RowItem extends Component {
  render(){
    //render styles and components conditionally using this.props.selected ? _ : _
    
    return (
      <TouchableOpacity onPress={this.props.onPressItem}>
        ...
      </TouchableOpacity>
    )
  }
}