react-native - 使用 REST 中的经度和纬度获取方向

Question

我想从 2 个点（起点和终点）获取方向，我编写了一个简单的函数来获取经度和纬度。

看起来像这样

const GetLongitudeFromAddress = (address) =>{
    var logLatApi = 'https://maps.googleapis.com/maps/api/geocode/json?address='+address+'&sensor=false&key=AIzaSyBsy6x3mTXbPQ52qk6XMI9u1NgMfn9-YNE';
    var header = {
        'Accept': 'application/json',
        'Content-Type': 'application/json'
    };
    fetch(
        logLatApi,{
            method : 'GET',
            headers : header
        }
    ).then((response) => response.json())
    .then((responseJson)=>{
        if(responseJson.status ==='OK')
        {
            this.setState({longitude: responseJson.results[0].geometry.location.lng});
            this.setState({latitude: responseJson.results[0].geometry.location.lat});
        }
    })
}

现在我想在 inputText 中使用它 像这样

            <TextInput 
            style={styles.input}
            placeholder="Origin"
            onChangeText={text => GetLongitudeFromAddress(text)}
            />

它似乎不起作用，我得到了这个错误可能承诺处理拒绝，如下图所示

如何将它与 useState 一起使用？我的代码如下所示：

import React , {useState, useEffect} from 'react';
import {StyleSheet, View, Dimensions, TextInput} from 'react-native';
import MapView , { Marker , Polyline } from 'react-native-maps';
import MapViewDirections from 'react-native-maps-directions';
import { GooglePlacesAutocomplete } from 'react-native-google-places-autocomplete';

const ShowMap =() =>{

    const GetLongitudeFromAddress = (address) =>{
        var logLatApi = 'https://maps.googleapis.com/maps/api/geocode/json?address='+address+'&sensor=false&key=AIzaSyBsy6x3mTXbPQ52qk6XMI9u1NgMfn9-YNE';
        var header = {
            'Accept': 'application/json',
            'Content-Type': 'application/json'
        };
        fetch(
            logLatApi,{
                method : 'GET',
                headers : header
            }
        ).then((response) => response.json())
        .then((responseJson)=>{
            if(responseJson.status ==='OK')
            {
                this.setState({longitude: responseJson.results[0].geometry.location.lng});
                this.setState({latitude: responseJson.results[0].geometry.location.lat});
            }
        })
    }

    const [coordinates] = useState([
        {
          latitude: 6.450430,
          longitude: 3.390460,
        },
        {
          latitude: 6.430980,
          longitude: 3.435880,
        },
      ]);

    return(
        
        <View style={styles.container}>
        <MapView
          style={styles.maps}
          initialRegion={{
            latitude: coordinates[0].latitude,
            longitude: coordinates[0].longitude,
            latitudeDelta: 0.0622,
            longitudeDelta: 0.0121,
          }}>
          <MapViewDirections
            origin={coordinates[0]}
            destination={coordinates[1]}
            apikey="AIzaSyBsy6x3mTXbPQ52qk6XMI9u1NgMfn9-YNE"
            strokeWidth={4}
            strokeColor="#FD0631"
          />
          <Marker coordinate={coordinates[0]} />
          <Marker coordinate={coordinates[1]} />
        </MapView>
        <View style={styles.inputView}>
                <TextInput 
                style={styles.input}
                placeholder="Origin"
                onChangeText={text => GetLongitudeFromAddress(text)}
                />
                <TextInput 
                style={styles.input}
                placeholder="Destination"
                onChangeText={text => GetLongitudeFromAddress(text)}
                />
            </View>
      </View>
    );
}


const styles = StyleSheet.create({
    container: {
      flex: 1,
    },
    maps: {
      width: Dimensions.get('screen').width,
      height: Dimensions.get('screen').height,
    },
    inputView:{
        backgroundColor: 'rgba(0,0,0,0)',
        position: 'absolute', 
        top: 0,
        left: 5,
        right: 5
    },
    input: {
        height: 50,
        padding: 10,
        marginTop: 20,
        marginLeft: 10,
        marginRight: 10,
        fontSize: 18,
        borderWidth: 1,
        borderRadius: 35,
        borderColor: '#EEEEEE',
        backgroundColor: 'white',
    }
  });



export default ShowMap;

我该怎么做？我如何使用它GetLongitudeFromAddress来获取两个领域的经度和纬度。请协助

标签： react-nativeuse-statedirections

Answer 1

您需要有一个按钮，GetLongitudeFromAddress在按下时会调用该函数。每次更改输入文本值时调用此函数的成本都会很高，因为每次调用该函数时都会调用地理编码请求。我成功地修改了您的代码以从输入文本中获取地址，然后使用该函数对其进行转换，然后将转换后的坐标用作 MapViewDirections 的输入。下面是一个示例代码和一个带有内联注释的代码片段：

import React, { useState, useEffect } from 'react';
import { StyleSheet, View, Dimensions, TextInput, Button } from 'react-native';
import MapView, { Marker, Polyline } from 'react-native-maps';
import MapViewDirections from 'react-native-maps-directions';
import { GooglePlacesAutocomplete } from 'react-native-google-places-autocomplete';
const { width, height } = Dimensions.get('window');
const ShowMap = () => {

//initial maps coordinate
  const [initialCenter] = useState({
    latitude: 6.45043,
    longitude: 3.39046,
  });

//state variables for the value of the textbox
  const [originInput, setOInput] = useState(null);
  const [destInput, setDInput] = useState(null);

//state variables to handle the coordinates after getting it from GetLongitudeFromAddress function
  const [originReq, setOReq] = useState(null);
  const [destReq, setDReq] = useState(null);

//state variable that will be one of the condition to trigger MapViewDirections once button is pressed
  const [isBtnPressed, setBtn] = useState(null);

  //state variable that will be a condition to show the origin and destination marker once the route was started
  const [routeStarted, setRouteStarted] = useState(null);

//function that will convert the address from your inpput textbox to a coordinate(geocoding)
//coord variable will be the variable that will determine if you are converting the origin or the destination coordinates
  const GetLongitudeFromAddress = (address, coord) => {
    var logLatApi =
      'https://maps.googleapis.com/maps/api/geocode/json?address=' +
      address +
      '&sensor=false&key=YOUR_KEY';
    var header = {
      Accept: 'application/json',
      'Content-Type': 'application/json',
    };
    fetch(logLatApi, {
      method: 'GET',
      headers: header,
    })
      .then((response) => response.json())
      .then((responseJson) => {
        if (responseJson.status === 'OK') {
          //check if coord value is 'origin' or destination'
          if (coord == 'origin' || coord == 'destination') {
            if (coord == 'origin') {
              //if origin, it will change the originReq state value to the result
              setOReq({
                latitude: responseJson.results[0].geometry.location.lat,
                longitude: responseJson.results[0].geometry.location.lng,
              });
            } else {
              //if destination, it will change the destReq state value to the result
              setDReq({
                latitude: responseJson.results[0].geometry.location.lat,
                longitude: responseJson.results[0].geometry.location.lng,
              });
            }
          }
        }
      });
 
  };

//function called when the button is pressed
  const processAddress = () => {
 //it will pass the current value of your input state and hardcoding origin or destination to mark if the address being converted to coordinates is either one of them
    GetLongitudeFromAddress(originInput, 'origin');
    GetLongitudeFromAddress(destInput, 'destination');
    //change isBtnPressed state variable value
    setBtn('Y');
  };

//function called when the route is ready, it will also fit the polyline to the current view
  const routeReady = (result) => {
    console.log(`Distance: ${result.distance} km`);
    console.log(`Duration: ${result.duration} min.`);
    console.log(isBtnPressed);
    this.mapView.fitToCoordinates(result.coordinates, {
      edgePadding: {
        right: width / 20,
        bottom: height / 20,
        left: width / 20,
        top: height / 20,
      },
    });
  };



  return (
    <View style={styles.container}>
      <MapView
        style={styles.maps}
        ref={(c) => (this.mapView = c)}
        initialRegion={{
          latitude: initialCenter.latitude,
          longitude: initialCenter.longitude,
          latitudeDelta: 0.0622,
          longitudeDelta: 0.0121,
        }}>
        {isBtnPressed !== null && originReq !== null && destReq !== null && (
          <MapViewDirections
            origin={originReq}
            destination={destReq}
            apikey="YOUR_KEY"
            strokeWidth={4}
            strokeColor="#FD0631"
            onStart={() => {
              setRouteStarted('Y');
            }}
            onReady={(result) => {
              routeReady(result);
            }}
            onError={() => {
              setRouteStarted(null);
            }}
          />
        )}
        {routeStarted !== null && originReq != null && (
          <Marker coordinate={originReq} />
        )}
        {routeStarted !== null && destReq != null && (
          <Marker coordinate={destReq} />
        )}
      </MapView>
      <View style={styles.inputView}>
        <TextInput
          style={styles.input}
          placeholder="Origin"
          onChangeText={(text) => setOInput(text)}
        />
        <TextInput
          style={styles.input}
          placeholder="Destination"
          onChangeText={(text) => setDInput(text)}
        />
        <Button title="Press me" color="#f194ff" onPress={processAddress} />
      </View>
    </View>
  );
};

const styles = StyleSheet.create({
  container: {
    flex: 1,
  },
  maps: {
    width: Dimensions.get('screen').width,
    height: Dimensions.get('screen').height,
  },
  inputView: {
    backgroundColor: 'rgba(0,0,0,0)',
    position: 'absolute',
    top: 0,
    left: 5,
    right: 5,
  },
  input: {
    height: 50,
    padding: 10,
    marginTop: 20,
    marginLeft: 10,
    marginRight: 10,
    fontSize: 18,
    borderWidth: 1,
    borderRadius: 35,
    borderColor: '#EEEEEE',
    backgroundColor: 'white',
  },
});

export default ShowMap;

注意：请在您的代码中删除您的 API 密钥，请勿将其分享到公共站点，以保护您的 API 密钥不被意外使用。