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Google Maps API - show popup Lat Lon at mouse click

Posted on 2007-12-02
Last Modified: 2010-01-30
I would like to show a popup on a Google Map that I have generated, via the APIs provided by Google and accessed via Javascript code.

This popup should show the Latitude and Longitude of the mouse click location on the map.

How do I do this via Javascript and the Google Map APIs ?

Question by:Donelson
  • 4
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LVL 82

Accepted Solution

hielo earned 500 total points
ID: 20398204
Refer to:

Specifically, look at the "Using Passed Arguments in Events" example. A slightly modified version of it is included below. The example below will call "processClick" with the latitude and longitude values upon click.
Hope this helps.
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN"
<html xmlns="http://www.w3.org/1999/xhtml" xmlns:v="urn:schemas-microsoft-com:vml">
    <meta http-equiv="content-type" content="text/html; charset=utf-8"/>
    <title>Google Maps JavaScript API Example: Event Arguments</title>
    <script src="http://maps.google.com/maps?file=api&amp;v=2&amp;key=ABQIAAAAzr2EBOXUKnm_jVnk0OJI7xSosDVG8KKPE1-m51RBrvYughuyMxQ-i1QfUnH94QxWIa6N4U6MouMmBA"
    <script type="text/javascript">
    function initialize() {
      if (GBrowserIsCompatible()) {
        var map = new GMap2(document.getElementById("map_canvas"));
        map.setCenter(new GLatLng(37.4419, -122.1419), 13);
        GEvent.addListener(map,"click", function(overlay,latlng) {     
          //var myHtml = "The GLatLng value is: " + map.fromLatLngToDivPixel(latlng) + " at zoom level " + map.getZoom();
          //map.openInfoWindow(latlng, myHtml);
		var coordinate = String(map.fromLatLngToDivPixel(latlng)).replace(/[\)\(]/g,"").split(", ");
		processClick( coordinate[0],coordinate[1] );
        map.addControl(new GSmallMapControl());
        map.addControl(new GMapTypeControl());
function processClick(latitude,longitude)
	alert("Latitude: " +latitude + "; Longitude:"+longitude);
  <body onload="initialize()" onunload="GUnload()">
    <div id="map_canvas" style="width: 500px; height: 300px"></div>

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Author Comment

ID: 20399411
Could you explain in english what this string proc does?

(map.fromLatLngToDivPixel(latlng)).replace(/[\)\(]/g,"").split(", ");

LVL 82

Expert Comment

ID: 20399529
OK, sure. This part:

will return the latitude and longitude as a string, but formatted as follows:
(234, 312)

The replace part is removing the leading and trailing parentheses.
The split part "breaks" apart "234, 312" at the ", " returning an array.
Ultimately "var coordinate " ends up receiving an array of two elements. The first is the latitude and the other is the longitude.

Then I just called my "generic" function with the coordinates.
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LVL 82

Expert Comment

ID: 20399568
Just so we are clear:
var coordinate = String(map.fromLatLngToDivPixel(latlng)).replace(/[\)\(]/g,"").split(", ");

could have been written as:

//get coordinates formatted as "(#, #)"
var coordinate = String(map.fromLatLngToDivPixel(latlng));

//remove leading and trailing parenthesis, leaving you with "#, #"
coordinate = coordinate.replace(/[\)\(]/g,"");

//break the string at the comma space. split returns its results in an array.
coordinate = coordinate.split(", ");

At this point: coordinate[0] contains the latitude; coordinate[1] contains the longitude.

Author Comment

ID: 20399570
Someone said there is a "point" function:

point.lat() --and-- point.lon()


LVL 82

Expert Comment

ID: 20403580
Donelson, I did a research based on you last post and there is a HUGE difference between String(map.fromLatLngToDivPixel(latlng)), and the Point methods.

The first Computes the pixel coordinates of the given geographical point in the DOM element that holds the draggable map. Tthe latter are he actual "earth" geographic values. Assuming you are interested in the latter, the code would need to bechanged as follows:
       GEvent.addListener(map,"click", function(overlay,latlng) {    
     processClick( latlng.lat(),latlng.lng() );

Author Comment

ID: 20404070

Much better. We both learned something !



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