您试图在对象上设置密钥,该对象是不可变的并且已被冻结

Question

在以下示例中:

• MapView显示ListView作为注释的元素
• 点击一个上ListView元素应导致画吧蓝颜色.
• 奖励如果MapView并且ListView有效地使用状态对象

在修改属性时,修改DataSourceof ListView似乎会导致冲突active:

您试图在对象上设置值为'active'且值为'false',该对象是不可变的并且已被冻结.

设置国家的正确方法是什么？

RNPlay示例

'use strict';

import React, {Component} from 'react';
import {AppRegistry,View,ListView,MapView,Text,TouchableOpacity} from 'react-native';

var annotations = [
        {
          title: 'A',active: false,latitude: 45,longitude: 26,latitudeDelta: 0.015,longitudeDelta: 0.015,
        },{
          title: 'B',active: false,latitude: 49,longitude: 14,latitudeDelta: 0.015,longitudeDelta: 0.015,
        },{
          title: 'C',active: false,latitude: 26,longitude: 25,latitudeDelta: 0.015,longitudeDelta: 0.015,
        }
      ]

class SampleApp extends Component {

  constructor(props) {
    super(props);
    var ds = new ListView.DataSource({
        rowHasChanged: (row1, row2) => row1 !== row2,
    });
    this.state = {
      region: annotations[0],
      annotations: annotations,
      dataSource: ds.cloneWithRows(annotations)
    };
  }

  handleClick(field) {
    if (this.previousField) {
      this.previousField.active = false;
    }
    this.previousField = field;
    field.active = true;
    this.setState({
      region: field,
    });
  }

  renderField(field) {
    let color = (field.active == true)?'blue':'yellow'; 

    return (
      <TouchableOpacity onPress={this.handleClick.bind(this,field)}>
        <Text style={{backgroundColor:color,borderWidth:1}}>{field.title}</Text>
      </TouchableOpacity>
    );
  }

  render() {
    return (
      <View style={{flex:1,flexDirection:'column',alignSelf:'stretch'}}>
        <MapView
            style={{flex:0.5,alignSelf:'stretch',borderWidth:1}}
          region={this.state.region}
          annotations={this.state.annotations}
        />
        <ListView
          dataSource={this.state.dataSource}
          renderRow={(field) => this.renderField(field)}
        />
      </View>
    );
  }
}

AppRegistry.registerComponent('SampleApp', () => SampleApp);

Answer 1

问题

当您设置field.active = true;或者this.previousField.active = false;,您正在修改field您的数据源中存在的对象()ListView.的ListView,因为当你创建它使用冻结其数据源引发错误cloneWithRows.这是为了确保不能在正常的React组件生命周期之外修改数据源(如setState).相反,ListView.DataSource对象设计为使用更改cloneWithRows,返回现有数据源的副本.

如果您熟悉Redux库,那么它与使用reducer函数返回状态副本而不是修改现有状态的理念非常相似.

克隆DataSource

要解决这个问题,不要改变函数中的field对象,而是handleClick要创建一个已设置值的新数据数组(如active),然后setState使用新ListView创建的数据源调用cloneWithRows.如果你这样做,你甚至根本不需要annotations你所在州的钥匙.

代码可能比这里的文字更有帮助:

handleClick(field) {

  //iterate over annotations, and update them.
  //I'm taking 'title' as a unique id property for each annotation, 
  //for the sake of the example.
  const newAnnotations = annotations.map(a => {
    //make a copy of the annotation.  Otherwise you'll be modifying
    //an object that's in your listView's datasource,
    //and therefore frozen.
    let copyA = {...a};
    if (copyA.title === field.title) {
      copyA.active = true;
    } else {
      copyA.active = false;
    }
    return copyA;
  });

  this.setState({
    region: {...field, active: true},
    dataSource: this.state.dataSource.cloneWithRows(newAnnotations),
  });
}

我希望这有帮助!这是一个代码片段,其中包含您发布的完整代码以及我的修改.正如你在iOS上使用React Native 0.29所描述的那样,它正在为我工​​作.你标记了android-mapview的问题,所以我假设你正在运行Android,但在这种情况下平台不应该真正有所作为.

'use strict';

import React, {Component} from 'react';
import {AppRegistry,View,ListView,MapView,Text,TouchableOpacity} from 'react-native';

var annotations = [
        {
          title: 'A',active: false,latitude: 45,longitude: 26,latitudeDelta: 0.015,longitudeDelta: 0.015,
        },{
          title: 'B',active: false,latitude: 49,longitude: 14,latitudeDelta: 0.015,longitudeDelta: 0.015,
        },{
          title: 'C',active: false,latitude: 26,longitude: 25,latitudeDelta: 0.015,longitudeDelta: 0.015,
        }
      ]

class SampleApp extends Component {

  constructor(props) {
    super(props);
    var ds = new ListView.DataSource({
        rowHasChanged: (row1, row2) => row1 !== row2,
    });
    this.state = {
      region: annotations[0],
      dataSource: ds.cloneWithRows(annotations)
    };
  }

  handleClick(field) {

    //iterate over annotations, and update them.
    //I'm taking 'title' as a unique id property for each annotation, 
    //for the sake of the example.
    const newAnnotations = annotations.map(a => {
      //make a copy of the annotation.  Otherwise you'll be modifying
      //an object that's in your listView's datasource,
      //and therefore frozen.
      let copyA = {...a};
      if (copyA.title === field.title) {
        copyA.active = true;
      } else {
        copyA.active = false;
      }
      return copyA;
    });

    this.setState({
      region: {...field, active: true},
      dataSource: this.state.dataSource.cloneWithRows(newAnnotations),
    });
  }

  renderField(field) {
    console.log(field);
    let color = (field.active == true)?'blue':'yellow';

    return (
      <TouchableOpacity onPress={this.handleClick.bind(this,field)}>
        <Text style={{backgroundColor:color,borderWidth:1}}>{field.title}</Text>
      </TouchableOpacity>
    );
  }

  render() {
    return (
      <View style={{flex:1,flexDirection:'column',alignSelf:'stretch'}}>
        <MapView
          style={{flex:0.5,alignSelf:'stretch',borderWidth:1}}
          region={this.state.region}
          annotations={this.state.annotations}
        />
        <ListView
          dataSource={this.state.dataSource}
          renderRow={(field) => this.renderField(field)}
        />
      </View>
    );
  }
}

AppRegistry.registerComponent('SampleApp', () => SampleApp);