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Working with Geolocation watchPosition() API

Working with Geolocation watchPosition() API

I’m going to share a working navigator.geolocation.watchPosition() code I used when I wanted the user to know his current location in real time (while he is walking or riding a vehicle).

This works while the user is using his Android device or any device with a browser that supports the Geolocation API.

We made this code with the help of Google Maps and jQuery.

Live Demo

Recommended to use a mobile device, you must allow it to get your current location, don’t worry, I’m not tracking you.

Code Example

Now here’s our index.html code.

<!DOCTYPE HTML>
<html>
<head>
    <title>Geolocation watchPosition() by The Code of a Ninja</title>
    
    <!-- for mobile view -->
    <meta content='width=device-width, initial-scale=1' name='viewport'/>
    
    <script src="//ajax.googleapis.com/ajax/libs/jquery/1.10.2/jquery.min.js" ></script>
    <script type="text/javascript" src="http://maps.google.com/maps/api/js?v=3&sensor=false&language=en"></script>
    <script type="text/javascript">

        // you can specify the default lat long
        var map,
            currentPositionMarker,
            mapCenter = new google.maps.LatLng(14.668626, 121.24295),
            map;

        // change the zoom if you want
        function initializeMap()
        {
            map = new google.maps.Map(document.getElementById('map_canvas'), {
               zoom: 18,
               center: mapCenter,
               mapTypeId: google.maps.MapTypeId.ROADMAP
             });
        }

        function locError(error) {
            // tell the user if the current position could not be located
            alert("The current position could not be found!");
        }

        // current position of the user
        function setCurrentPosition(pos) {
            currentPositionMarker = new google.maps.Marker({
                map: map,
                position: new google.maps.LatLng(
                    pos.coords.latitude,
                    pos.coords.longitude
                ),
                title: "Current Position"
            });
            map.panTo(new google.maps.LatLng(
                    pos.coords.latitude,
                    pos.coords.longitude
                ));
        }

        function displayAndWatch(position) {
        
            // set current position
            setCurrentPosition(position);
            
            // watch position
            watchCurrentPosition();
        }

        function watchCurrentPosition() {
            var positionTimer = navigator.geolocation.watchPosition(
                function (position) {
                    setMarkerPosition(
                        currentPositionMarker,
                        position
                    );
                });
        }

        function setMarkerPosition(marker, position) {
            marker.setPosition(
                new google.maps.LatLng(
                    position.coords.latitude,
                    position.coords.longitude)
            );
        }

        function initLocationProcedure() {
            initializeMap();
            if (navigator.geolocation) {
                navigator.geolocation.getCurrentPosition(displayAndWatch, locError);
            } else {
                // tell the user if a browser doesn't support this amazing API
                alert("Your browser does not support the Geolocation API!");
            }
        }

        // initialize with a little help of jQuery
        $(document).ready(function() {
            initLocationProcedure();
        });
    </script>
</head>

<body style="margin:0; padding:0;">
    
    <!-- display the map here, you can changed the height or style -->
    <div id="map_canvas" style="height:25em; margin:0; padding:0;"></div>
</body>

</html>

In my case, I used this code with an Android WebView since it should be seen inside an app I’m working on, but as I said, this will work with any device with a browser.

If you have the same case as mine, you can also use this piece of android WebView code.

Just add:

webSettings.setGeolocationEnabled(true);

and inside your setWebChromeClient()…

@Override
public void onGeolocationPermissionsShowPrompt(String origin, GeolocationPermissions.Callback callback) {
    
    super.onGeolocationPermissionsShowPrompt(origin, callback);
    callback.invoke(origin, true, false);
}

Download Source Code

You can download all the code used in this tutorial for only $9.99 $5.55!

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Issues Encountered

If you were testing it with an Adroid Webview or Chrome Browser and seemed like it is not working, don’t lose hope. There is always hope. :)

Here’s the solution, uninstall the Chrome browser and then re-install it.

Related Source Code

Google Maps Geocoding Example with PHP – This tutorial is about a Google Maps geocoding example with PHP. We used some Google Maps JavaScript to show the geo-coded data on the map as well.

Further Reading

Geolocation API Specification
Geolocation.watchPosition() from Mozilla Developer Network

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