Question

我正在尝试从服务器动态获取附近的标记并在地图上打印但没有成功。当我更新地图位置时，我会收到警告。当我拖动地图时，预期的行为是在地图上打印标记，但它没有显示任何动态提取的标记，但显示警告。

20:27:15：[未处理的承诺拒绝：TypeError：undefined不是对象（评估＆＃39; object [key]＆＃39;）] - node_modules / immutability-helper / index.js：81：44 in - 更新中的node_modules / immutability-helper / index.js：73：29 - ......来自框架内部的16个堆栈框架

App.js（主文件）

import React, { Component } from 'react';
import { Text, View, StyleSheet, Switch, Alert, AppRegistry } from 'react-native';
import MapView from 'react-native-maps';
import Fetchdata from './Fetchdata.js';

const styles = StyleSheet.create({
  container: {
    ...StyleSheet.absoluteFillObject,
    height: 400,
    width: 400,
    justifyContent: 'flex-end',
    alignItems: 'center',
  },
  map: {
    ...StyleSheet.absoluteFillObject,
  },
});

export default class myScreen extends Component {
  render() {
    return (
      <View style ={styles.container}>
        <Fetchdata />
      </View>
    );
  }
}

Fetchdata.js（获取服务器数据的文件）

import React, { Component } from 'react'
import { Text, View, StyleSheet, Switch, Alert, AppRegistry} from 'react-native'
import MapView, {Marker, ProviderPropType} from 'react-native-maps';
import update from 'immutability-helper';

const styles = StyleSheet.create({
  container: {
    ...StyleSheet.absoluteFillObject,
    height: 400,
    width: 400,
    justifyContent: 'flex-end',
    alignItems: 'center',
  },
  map: {
    ...StyleSheet.absoluteFillObject,
  },
});
export default class Fetchdata extends Component {
  constructor (props) {
    super(props);
  };

  state = {
    latitude: 40.3565,
    longitude: 27.9774,
    markers: [
      {
        key: 1,
        latlng: {
          latitude: 40.3565,
          longitude: 27.9774
        }
      }
    ]
  };
  componentDidMount = () => {
    navigator.geolocation.getCurrentPosition(
        (position) => {
          this.setState({
            latitude: position.coords.latitude,
            longitude: position.coords.longitude,
            error: null,
      });
    },
      (error) => this.setState({ error: error.message }),
      { enableHighAccuracy: true, timeout: 20000, maximumAge: 1000 },
    );
   }
   onRegionChange (region) {
       fetch('https://isg.info.tr/query_maps.php' + '?latitude=' + region.latitude + '&longitude=' + region.longitude , {method: 'GET'})
        .then((response) => response.json())
        .then((responseJson) => {
          var newlatlng;
          for (i = 0 ; i< responseJson.length; i++) {
            newlatlng = update(this.state, {markers: { 
                                                        key: { $set: i }, 
                                                        latlng: { latitude: { $set: responseJson.latitude },
                                                        longitude: { $set:  responseJson.longitude  } 
                                                      } 
                                            }        
                                          });
            this.setState({markers});
          }
        })
   };
   render() {
      return (
        <View style={styles.container}>
          <MapView
                style={styles.map}
                initialRegion={{
                latitude: this.state.latitude,
                longitude: this.state.longitude,
                latitudeDelta: 0.015,
                longitudeDelta: 0.015,
            }}
            onRegionChange={this.onRegionChange.bind(this)}
            >
            {this.state.markers.map((marker, index) => (
              <MapView.Marker key={index} coordinate={marker.latlng} title={'marker.title'} />
            ))}
          </MapView>
      </View>
      );
   }
}
Fetchdata.propTypes = {
  provider: ProviderPropType,
};

Jsondata从服务器获取：

[{"latlng":{"latitude":"40.3565","longitude":"27.9774"}},{"latlng":{"latitude":"40.3471","longitude":"27.9598"}},{"latlng":{"latitude":"40","longitude":"27.9708"}}]

Answer 1

我不确定更新功能，但在这里您要分配未定义的值：

latlng：{latitude：{$ set：responseJson.latitude}，经度：{$ set：responseJson.longitude}

responseJson没有孩子的经纬度。他们有LatLng

React Native Map - 从服务器获取标记

1 个答案: