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Retrieve latitude and longitude of a draggable pin via Google Maps API V3

问题描述:

I will explain. I managed to have a draggable pin on a map. I want to retrieve the coordinates of this point and put them into two fields: Latitude and Longitude. These coordinates will later be send to a SQL table via PHP.

Here is an example of what I intend to do, but instead of several pins, it's just one and it's draggable. The problem is: I'm not even able to display the coordinates of the initial point. And of course when the user moves the pin, I want the coordinates to change as well in the fields.

I hope I made myself clear. What did I do wrong? Should I use the Geocoding service?

Here goes the JS:

<script type="text/javascript">

var map;

function initialize() {

var myLatlng = new google.maps.LatLng(40.713956,-74.006653);

var myOptions = {

zoom: 8,

center: myLatlng,

mapTypeId: google.maps.MapTypeId.ROADMAP

}

map = new google.maps.Map(document.getElementById("map_canvas"), myOptions);

var marker = new google.maps.Marker({

draggable: true,

position: myLatlng,

map: map,

title: "Your location"

});

google.maps.event.addListener(marker,'click',function(overlay,point){

document.getElementById("latbox").value = lat();

document.getElementById("lngbox").value = lng();

});

}

</script>

And the HTML:

<html>

<body onload="initialize()">

<div id="map_canvas" style="width:50%; height:50%"></div>

<div id="latlong">

<p>Latitude: <input size="20" type="text" id="latbox" name="lat" ></p>

<p>Longitude: <input size="20" type="text" id="lngbox" name="lng" ></p>

</div>

</body>

</html>

网友答案:

Either of these work

google.maps.event.addListener(marker, 'click', function (event) {
    document.getElementById("latbox").value = event.latLng.lat();
    document.getElementById("lngbox").value = event.latLng.lng();
});

google.maps.event.addListener(marker, 'click', function (event) {
    document.getElementById("latbox").value = this.getPosition().lat();
    document.getElementById("lngbox").value = this.getPosition().lng();
});

You might also consider using the dragend event also

google.maps.event.addListener(marker, 'dragend', function (event) {
    document.getElementById("latbox").value = this.getPosition().lat();
    document.getElementById("lngbox").value = this.getPosition().lng();
});
网友答案:

Look at the official code sample from Google Maps API reference: http://gmaps-samples-v3.googlecode.com/svn/trunk/draggable-markers/draggable-markers.html

网友答案:

The code that is actually working is the following:

google.maps.event.addListener(marker, 'drag', function(event){
       document.getElementById("latbox").value = event.latLng.lat();
       document.getElementById("lngbox").value = event.latLng.lng();
});

It would be better if the map could be re-centered once the pin is dropped. I guess it can be done with map.setCenter() but I'm not sure where I should put it. I tried to put it right before and right after this piece of code but it won't work.

网友答案:

Google Maps V3 Example. Here's a working example of a user dropping a single pin, replacing a dropped pin with new pin, custom pin images, pins that populate lat/long values in a FORM FIELD within a DIV.

<html>
<body onLoad="initialize()">

  <div id="map_canvas" style="width:50%; height:50%"></div>

  <div id="latlong">
    <p>Latitude: <input size="20" type="text" id="latbox" name="lat" ></p>
    <p>Longitude: <input size="20" type="text" id="lngbox" name="lng" ></p>
  </div>

</body>
</html>

<cfoutput>
    <script type="text/javascript" src="http://maps.googleapis.com/maps/api/js?key=#YOUR-GOOGLE-API-KEY#&sensor=false"></script>
</cfoutput>

<script type="text/javascript">
//<![CDATA[

    // global "map" variable
    var map = null;
    var marker = null;

    // popup window for pin, if in use
    var infowindow = new google.maps.InfoWindow({ 
        size: new google.maps.Size(150,50)
        });

    // A function to create the marker and set up the event window function 
    function createMarker(latlng, name, html) {

    var contentString = html;

    var marker = new google.maps.Marker({
        position: latlng,
        map: map,
        zIndex: Math.round(latlng.lat()*-100000)<<5
        });

    google.maps.event.addListener(marker, 'click', function() {
        infowindow.setContent(contentString); 
        infowindow.open(map,marker);
        });

    google.maps.event.trigger(marker, 'click');    
    return marker;

}

function initialize() {

    // the location of the initial pin
    var myLatlng = new google.maps.LatLng(33.926315,-118.312805);

    // create the map
    var myOptions = {
        zoom: 19,
        center: myLatlng,
        mapTypeControl: true,
        mapTypeControlOptions: {style: google.maps.MapTypeControlStyle.DROPDOWN_MENU},
        navigationControl: true,
        mapTypeId: google.maps.MapTypeId.ROADMAP
    }

    map = new google.maps.Map(document.getElementById("map_canvas"), myOptions);

    // establish the initial marker/pin
    var image = '/images/googlepins/pin2.png';  
    marker = new google.maps.Marker({
      position: myLatlng,
      map: map,
      icon: image,
      title:"Property Location"
    });

    // establish the initial div form fields
    formlat = document.getElementById("latbox").value = myLatlng.lat();
    formlng = document.getElementById("lngbox").value = myLatlng.lng();

    // close popup window
    google.maps.event.addListener(map, 'click', function() {
        infowindow.close();
        });

    // removing old markers/pins
    google.maps.event.addListener(map, 'click', function(event) {
        //call function to create marker
         if (marker) {
            marker.setMap(null);
            marker = null;
         }

        // Information for popup window if you so chose to have one
        /*
         marker = createMarker(event.latLng, "name", "<b>Location</b><br>"+event.latLng);
        */

        var image = '/images/googlepins/pin2.png';
        var myLatLng = event.latLng ;
        /*  
        var marker = new google.maps.Marker({
            by removing the 'var' subsquent pin placement removes the old pin icon
        */
        marker = new google.maps.Marker({   
            position: myLatLng,
            map: map,
            icon: image,
            title:"Property Location"
        });

        // populate the form fields with lat & lng 
        formlat = document.getElementById("latbox").value = event.latLng.lat();
        formlng = document.getElementById("lngbox").value = event.latLng.lng();

    });

}
//]]>

</script> 
网友答案:

Check this fiddle

In the following code replace dragend with the event you want. In your case 'click'

google.maps.event.addListener(marker, 'dragend', function (event) {
    document.getElementById("defaultLatitude").value = event.latLng.lat();
    document.getElementById("defaultLongitude").value = event.latLng.lng();
});
网友答案:
google.maps.event.addListener(marker, 'dragend', function (event) {
    document.getElementById("latbox").value = this.getPosition().lat();
    document.getElementById("lngbox").value = this.getPosition().lng();
}); 

worked well for me.. Thanks..

网友答案:
    var zoomLevel = map.getZoom();
    var pos = (event.latLng).toString();

    $('#position').val(zoomLevel+','+pos); //set value to some input

Example Run JsFiddle

网友答案:

tRy This :)

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
<!--
develop by manoj sarnaik
 -->
<html xmlns="http://www.w3.org/1999/xhtml" xmlns:v="urn:schemas-microsoft-com:vml">
  <head>
    <meta http-equiv="content-type" content="text/html; charset=UTF-8"/>
    <title>Manoj Sarnaik</title>
    <script src="http://maps.google.com/maps?file=api&amp;v=2&amp;key=ABQIAAAAjU0EJWnWPMv7oQ-jjS7dYxSPW5CJgpdgO_s4yyMovOaVh_KvvhSfpvagV18eOyDWu7VytS6Bi1CWxw"
      type="text/javascript"></script>
    <script type="text/javascript">

    var map = null;
    var geocoder = null;

    function initialize() {
      if (GBrowserIsCompatible()) {
        map = new GMap2(document.getElementById("map_canvas"));
        map.setCenter(new GLatLng(20.236046, 76.988255), 1);
        map.setUIToDefault();
        geocoder = new GClientGeocoder();
      }
    }

    function showAddress(address) {
      if (geocoder) {
        geocoder.getLatLng(
          address,
          function(point) {
            if (!point) {
              alert(address + " not found");
            } else {
              map.setCenter(point, 15);
              var marker = new GMarker(point, {draggable: true});
              map.addOverlay(marker);
              GEvent.addListener(marker, "dragend", function() {
                marker.openInfoWindowHtml(marker.getLatLng().toUrlValue(6));
              });
              GEvent.addListener(marker, "click", function() {
                marker.openInfoWindowHtml(marker.getLatLng().toUrlValue(6));
              });
          GEvent.trigger(marker, "click");
            }
          }
        );
      }
    }
    </script>
  </head>

  <body onload="initialize()" onunload="GUnload()">
    <form action="#" onsubmit="showAddress(this.address.value); return false">

      <p>
        <input type="text" style="width:350px" name="address" value="Malegaon,washim" />
        <input type="submit" value="Go!" />
      </p>
      <div id="map_canvas" style="width: 600px; height: 400px"></div>
    </form>

  </body>
</html>
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