当我使用“position.coords.latitude”试图获得当前位置时，我得到了一个undefined

Question

我是新来的Ionic2，我按照这个教程，它完美地工作https://www.joshmorony.com/create-a-nearby-places-list-with-google-maps-in-ionic-2-part-1/，它列出了一些地方，然后计算距离在这些地方和硬编码的地方之间，我想要实现的是使用当前位置而不是代码中给出的位置，以下是我迄今取得的屏幕截图screenshot of my application 以下是我的位置提供程序：

import { Injectable } from '@angular/core'; 
 
import { Http } from '@angular/http'; 
 
import 'rxjs/add/operator/map'; 
 
import {Geolocation} from '@ionic-native/geolocation'; 
 

 
/* 
 
    Generated class for the LocationsProvider provider. 
 

 
    See https://angular.io/docs/ts/latest/guide/dependency-injection.html 
 
    for more info on providers and Angular 2 DI. 
 
*/ 
 
@Injectable() 
 
export class LocationsProvider { 
 

 
    data: any; 
 
    Currentlatitude: any; 
 
    Currentlongitude: any; 
 
    
 

 
    constructor(public http: Http, public geolocation: Geolocation) { 
 
     console.log('Hello LocationsProvider Provider'); 
 
    } 
 

 
    load(){  
 
     this.geolocation.watchPosition().subscribe((position) => { 
 
      this.Currentlatitude = position.coords.latitude; 
 
      this.Currentlongitude = position.coords.longitude;     
 
     }); 
 

 
     if(this.data){ 
 
      return Promise.resolve(this.data); 
 
     } 
 
    
 
     return new Promise(resolve => {  
 
      this.http.get('assets/data/locations.json').map(res => res.json()).subscribe(data => {  
 
       this.data = this.applyHaversine(data.locations);  
 
       this.data.sort((locationA, locationB) => { 
 
        return locationA.distance - locationB.distance; 
 
       });  
 
       resolve(this.data); 
 
      });  
 
     });  
 
    } 
 
    
 
    applyHaversine(locations){ 
 
    // this must change according to the device location 
 
    /* 
 

 
     let usersLocation = { 
 
      lat: 40.713744, 
 
      lng: -74.009056 
 
     }; */ 
 

 
     console.log("this.Currentlatitude ",this.Currentlatitude); 
 
    
 
     let usersLocation = { 
 
      latitude: this.Currentlatitude, 
 
      longitude: this.Currentlongitude 
 
     }; 
 

 
     console.log("usersLocation.latitude ",usersLocation.latitude); 
 
     locations.map((location) => { 
 
      let placeLocation = { 
 
       latitude: location.latitude, 
 
       longitude: location.longitude 
 
      }; 
 

 
      location.distance = this.getDistanceBetweenPoints(usersLocation, placeLocation, 'km').toFixed(2);    
 
     }); 
 

 
     return locations; 
 
    } 
 
    
 
    getDistanceBetweenPoints(start, end, units){  
 
     let earthRadius = { 
 
      miles: 3958.8, 
 
      km: 6371 
 
     }; 
 
    
 
     let R = earthRadius[units || 'km']; 
 
      
 
     let lat1 = start.latitude; 
 
     
 
     let lon1 = start.longitude; 
 
     
 
     let lat2 = end.latitude; 
 
      
 
     let lon2 = end.longitude; 
 
     console.log("lon1 ",lat1); // here it gives me undefined 
 

 
     let dLat = this.toRad((lat2 - lat1)); 
 
      
 
     let dLon = this.toRad((lon2 - lon1)); 
 
      
 
     let a = Math.sin(dLat/2) * Math.sin(dLat/2) + 
 
     Math.cos(this.toRad(lat1)) * Math.cos(this.toRad(lat2)) * 
 
     Math.sin(dLon/2) * 
 
     Math.sin(dLon/2); 
 
     
 
     let c = 2 * Math.atan2(Math.sqrt(a), Math.sqrt(1 - a)); 
 
     let d = R * c; 
 
      
 
     return d;  
 
    } 
 
    
 
    toRad(x){    
 
     return x * Math.PI/180; 
 
    }  
 
}

Answer 1

我想通的事情了地址（坐标或正常地址）之间的距离/时间，我的问题是，我没在使用Ionic中的Promises和Observables时，我不理解同步和异步任务，对于那些有同样问题的人，我建议本教程解释https://www.joshmorony.com/dealing-with-asynchronous-code-in-ionic/。 至于我的程序的解决方案，我发现这个问题的解决方案Get current position in ionic2

Answer 2

我最近为我的应用程序提供了位置服务。我使用地理定位插件，让我的当前位置，并从谷歌distancematrix API映射去

import { Query } from '../models/query'; 
import { Injectable } from '@angular/core'; 
import { Http } from '@angular/http'; 
import 'rxjs/add/operator/map'; 
import { Geolocation, Geoposition, Coordinates } from '@ionic-native/geolocation'; 
import { NativeGeocoder, NativeGeocoderReverseResult, NativeGeocoderForwardResult } from '@ionic-native/native-geocoder'; 

@Injectable() 
export class LocationService { 

    google_API_KEY: string = 'API_KEY_FROM_GOOGLE_GOES_HERE'; 
    currentLocation: Geoposition; 

    constructor(public http: Http, private geolocation: Geolocation, 
    private geocoder: NativeGeocoder) { 
    // Set your current location here, or remove this and set it manually throughout the app 
    this.setCurrentLocation(); 
    } 


    setCurrentLocation() { 
    return this.geolocation.getCurrentPosition().then((resp) => { 
     // Manipulate resp here if needed 
     this.currentLocation = resp; 
     console.log(JSON.stringify(this.currentLocation)); 
    }).catch((error) => { 
     console.log('Error getting location', error); 
    }) 
    } 

    getBetweenCoordsDetails(fromString: string, toString: string) { 
    let query = new Query('https://maps.googleapis.com/maps/api/distancematrix/json'); 
    query.add('key', this.google_API_KEY); 
    query.add('destinations', toString); 
    query.add('origins', fromString); 
    query.add('units', 'imperial'); 
    return this.http.get(query.toQuery()) 
     .do(resp => { 
     let x = resp; 
     }, error => { 
     let x = error; 
     }) 

    } 

    getBetweenCoordAndHereDetails(toString: string) { 
    let x = this.currentLocation.coords; 
    return this.getBetweenCoordsDetails(this.currentLocation.coords.latitude + ',' + this.currentLocation.coords.longitude, toString); 
    } 

    getCoordinatesFromAddress(address: string) { 
    return this.geocoder.forwardGeocode(address); 
    } 

}