How To Display Multiple Markers Coordinates Stored In Firebase Database On Google Maps

问题

I am trying to get the coordinates that are saved in the firebase real-time database and display them on a map using the google maps API. This is the code I have so far. Right now it opens and shows the users current location using the html5 geolocation API and it syncs the lat and long coordinates to the firebase real-time database using Geofire.

I don't know how to retrieve these points and have multiple points on the google map at the same time showing different users locations. If anyone could help me with this I would really appreciate it.

<script src="https://cdn.firebase.com/libs/geofire/4.1.2/geofire.min.js"></script>
<script src="https://www.gstatic.com/firebasejs/4.12.1/firebase.js"></script>
<!DOCTYPE html>
<html>
  <head>
    <title>Geolocation</title>
    <meta name="viewport" content="initial-scale=1.0, user-scalable=no">
    <meta charset="utf-8">
    <style>
      /* Always set the map height explicitly to define the size of the div
       * element that contains the map. */
      #map {
        height: 100%;
      }
      /* Optional: Makes the sample page fill the window. */
      html, body {
        height: 100%;
        margin: 0;
        padding: 0;
      }
    </style>
    <!-- Place this inside the HTML head; don't use async defer for now -->
<script src="https://www.gstatic.com/firebasejs/4.12.1/firebase.js"></script>
<script src="https://cdn.firebase.com/libs/geofire/4.1.2/geofire.min.js"></script>

  <script>
        
        var config = {
    apiKey: "AIzaSyCWZjRe2CK8Hu2VN35AgZOQ7lQZKcI-UWM",
    authDomain: "carrier-35d7c.firebaseapp.com",
    databaseURL: "https://carrier-35d7c.firebaseio.com",
    projectId: "carrier-35d7c",
    storageBucket: "carrier-35d7c.appspot.com",
    messagingSenderId: "827792028763"
  };

        if (!firebase.apps.length) {
            firebase.initializeApp(config);
        }
        
        //Create a node at firebase location to add locations as child keys
        var locationsRef = firebase.database().ref("locations");
        
        // Create a new GeoFire key under users Firebase location
        var geoFire = new GeoFire(locationsRef.push());
      </script>


  </head>
  <body>
    <div id="map"></div>
    <script>
      // Note: This example requires that you consent to location sharing when
      // prompted by your browser. If you see the error "The Geolocation service
      // failed.", it means you probably did not give permission for the browser to
      // locate you.

      var map, infoWindow;
      var lat, lng;
      function initMap() {
        map = new google.maps.Map(document.getElementById('map'), {
          center: {lat: -34.397, lng: 150.644},
          zoom: 18
        });
        infoWindow = new google.maps.InfoWindow;

        // Try HTML5 geolocation.
        if (navigator.geolocation) {
          navigator.geolocation.getCurrentPosition(function(position) {
            lat = position.coords.latitude;
            lng = position.coords.longitude;

            var pos = {lat: lat, lng: lng };
                _setGeoFire();
          

            infoWindow.setPosition(pos);
            infoWindow.setContent('Location found.');
            infoWindow.open(map);
            map.setCenter(pos);
          }, function() {
            handleLocationError(true, infoWindow, map.getCenter());
          });
        } else {
          // Browser doesn't support Geolocation
          handleLocationError(false, infoWindow, map.getCenter());
        }
      }

      function handleLocationError(browserHasGeolocation, infoWindow, pos) {
        infoWindow.setPosition(pos);
        infoWindow.setContent(browserHasGeolocation ?
                              'Error: The Geolocation service failed.' :
                              'Error: Your browser doesn\'t support geolocation.');
        infoWindow.open(map);
      }

      function _setGeoFire(){
    geoFire.set("User", [lat, lng]).then(()=>{
            console.log("Location added");
        }).catch(function(error) {
            console.log(error);
        });


}
    </script>
    <script 
    src="https://maps.googleapis.com/maps/api/js?key=AIzaSyD2nPlSt_nM7PSKD8So8anbUbBYICFWcCA&callback=initMap">
    </script>
  </body>
</html>

回答1:

Related question:

How to retrieve data from Firebase using Javascript?

I only get one result from that database:

c20ej76jhb
45.546058,-122.813203

Using this code (uses on rather than once) with a reference to a database I created with multiple locations (and a different format of data):

var locationsRef = firebase.database().ref("locations");
locationsRef.on('child_added', function(snapshot) {
var data = snapshot.val();
var marker = new google.maps.Marker({
  position: {
    lat: data.lat,
    lng: data.lng
  },
  map: map
});
bounds.extend(marker.getPosition());
marker.addListener('click', (function(data) {
  return function(e) {
    infowindow.setContent(data.name + "<br>" + this.getPosition().toUrlValue(6) + "<br>" + data.message);
    infowindow.open(map, this);
  }
}(data)));
map.fitBounds(bounds);

});

proof of concept fiddle

from your database:

from mine (with multiple locations and the modified code above):

code snippet:

function initialize() {
  var infowindow = new google.maps.InfoWindow();
  var map = new google.maps.Map(
    document.getElementById("map_canvas"), {
      center: new google.maps.LatLng(37.4419, -122.1419),
      zoom: 13,
      mapTypeId: google.maps.MapTypeId.ROADMAP
    });
  // Initialize Firebase
  var config = {
    apiKey: "AIzaSyC8HcClvIT_FlG8ZwCji4LG-qNx8D9VCrs",
    authDomain: "geocodeziptest.firebaseapp.com",
    databaseURL: "https://geocodeziptest.firebaseio.com",
    projectId: "geocodeziptest",
    storageBucket: "geocodeziptest.appspot.com",
    messagingSenderId: "1096545848604"
  };
  firebase.initializeApp(config);
  //Create a node at firebase location to add locations as child keys
  var locationsRef = firebase.database().ref("locations");
  var bounds = new google.maps.LatLngBounds();
  locationsRef.on('child_added', function(snapshot) {
    var data = snapshot.val();
    console.log(data);
    var marker = new google.maps.Marker({
      position: {
        lat: data.lat,
        lng: data.lng
      },
      map: map
    });
    bounds.extend(marker.getPosition());
    marker.addListener('click', (function(data) {
      return function(e) {
        infowindow.setContent(data.name + "<br>" + this.getPosition().toUrlValue(6) + "<br>" + data.message);
        infowindow.open(map, this);
      }
    }(data)));
    map.fitBounds(bounds);
  });
}
google.maps.event.addDomListener(window, "load", initialize);

html,
body,
#map_canvas {
  height: 100%;
  width: 100%;
  margin: 0px;
  padding: 0px
}

<script src="https://maps.googleapis.com/maps/api/js?key=AIzaSyCkUOdZ5y7hMm0yrcCQoCvLwzdM6M8s5qk"></script>
<script src="https://www.gstatic.com/firebasejs/4.12.1/firebase.js"></script>
<script src="https://cdn.firebase.com/libs/geofire/4.1.2/geofire.min.js"></script>
<div id="map_canvas"></div>

来源：https://stackoverflow.com/questions/49641049/how-to-display-multiple-markers-coordinates-stored-in-firebase-database-on-googl

标签

html

firebase

google-maps-api-3

firebase-realtime-database

geofire