WRT GPS undefined

[gurmukh]

Hi Guys

I am developing a service that reports the GPS co-ordinates of the device. However, there are times when the device reports location is found, but then the values of latitude and longitude are "undefined". Looking at the docs:

[criteria.Updateoptions.PartialUpdates] Specifies whether longitude, latitude, and altitude information is always guaranteed. http://library.forum.nokia.com/index...1C4378307.html

This is set to false, so I assume I would ALWAYS get a value? Here is a code snippet



function getLocationAsync() {

// Show notification status
uiManager.showNotification(-1, "wait", "Trying to get GPS fix...", 0.1);

// Disable partial updates so result returned is accurate GPS location.
var updateoptions = new Object();
updateoptions.PartialUpdates = false;
updateoptions.UpdateTimeOut = 60000000;
criteria.Updateoptions = updateoptions;


try {
// Create service object
so = device.getServiceObject("Service.Location", "ILocation");

// Create asynchronous method to call "callbackLocation" once GPS co-ordinates are known.
so.ILocation.GetLocation(criteria,callbackLocation);

} catch (e) {
uiManager.showNotification(-1, "wait", "getLocationAsync: " + e, 0.1);
}
}

function callbackLocation(transId, eventCode, result){

// Update global variable gotLocation and cancel asynchronous method.
if (gotLocation == false) {
gotLocation = true;
latitude = result.ReturnValue.Latitude;
longitude = result.ReturnValue.Longitude;
criteria.CancelRequestType="GetLocCancel";
result = so.ILocation.CancelNotification(criteria);
alert(longitude+latitude); // returns undefinedundefined
}
// Notify user GPS co-ordinates are found.
uiManager.showNotification(-1, "wait", "Got it!", 0.3);

// Get updated JSON object
getJson();
}

Any advice would be great!

[jzferreira]

Ok. I don't understand what is the problem, but follow a code which works for me:

var test = test || {};

/**
 * TODO
 */
test.location = {
    _so: null,
    init: function(){
        try {
            this._so = device.getServiceObject("Service.Location", "ILocation");
        } 
        catch (e) {
        
        }
    },
    getLocation: function(callbackSuccess, callbackError){
    
        try {
            var updateoptions = {};
            
            updateoptions.PartialUpdates = false;
            
            var criteria = {};
            criteria.LocationInformationClass = "GenericLocationInfo";
            criteria.Updateoptions = updateoptions;
            
            var result = this._so.ILocation.Trace(criteria, function(transId, eventCode, result){
            
                if (result.ErrorCode && result.ErrorCode !== 0) {
                    //ERROR
                    response = {
                        'error': result.ErrorMessage,
                        'code': result.ErrorCode
                    };
                    
                    callbackError.call(this, response);
                    
                }
                else {
                    //SUCCESS			
                    response = {
                        'success': 'Success Location',
                        'code': result.ErrorCode,
                        'longitude': result.ReturnValue.Longitude,
                        'latitude': result.ReturnValue.Latitude
                    };
                    
                    callbackSuccess.call(this, response);
                }
                
            });
            
            var errCode = result.ErrorCode;
            
            var response = null;
            
            if (errCode && errCode != 0) {
            
                response = {
                    'error': result.ErrorMessage,
                    'code': result.ErrorCode
                };
                callbackError.call(this, response);
            }
        } 
        catch (e) {
        
        }
        
    }
};

[gurmukh]

Thanks Javier

The difference I see with your code is that you are using the Trace approach and also are not cancelling the request once the initial co-ordinates are found.

[LWCARAB]

Hello,

I'm totally new to widget development and JavaScript to but I'm basically tring to play around with stuff and get my gps to return something, I've tried using your code and added some print lines but I don't get anything... any advice?

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
    <head>
        <title>Sample Widget</title>
		    <meta http-equiv="Content-Type" content="text/html; charset=UTF-8" />
        <link href="basic.css" rel="stylesheet" type="text/css" />
        
        <meta name="generator" content="Nokia WRT extension for Visual Studio 2.0" />
    </head>
    <body >
        <script type="text/javascript">
        var test = test || {};

        /**
        * TODO
        */
        test.location = {
            _so: null,
            init: function() {
                try {
                    this._so = device.getServiceObject("Service.Location", "ILocation");
                }
                catch (e) {

                }
            },
            getLocation: function(callbackSuccess, callbackError) {

                try {
                    var updateoptions = {};

                    updateoptions.PartialUpdates = false;

                    var criteria = {};
                    criteria.LocationInformationClass = "GenericLocationInfo";
                    criteria.Updateoptions = updateoptions;

                    var result = this._so.ILocation.Trace(criteria, function(transId, eventCode, result) {
                        document.write(result.ErrorCode);

                        if (result.ErrorCode && result.ErrorCode !== 0) {
                            //ERROR
                            response = {
                                'error': result.ErrorMessage,
                                'code': result.ErrorCode
                            };

                            callbackError.call(this, response);

                        }
                        else {
                            //SUCCESS			
                            response = {
                                'success': 'Success Location',
                                'code': result.ErrorCode,
                                'longitude': result.ReturnValue.Longitude,
                                'latitude': result.ReturnValue.Latitude
                            };

                            callbackSuccess.call(this, response);
                            document.write(response);
                        }

                    });

                    var errCode = result.ErrorCode;

                    var response = null;

                    if (errCode && errCode != 0) {

                        response = {
                            'error': result.ErrorMessage,
                            'code': result.ErrorCode
                        };
                        callbackError.call(this, response);
                    }
                }
                catch (e) {

                }

            }
        };
        </script>
	</body>
</html>

[isalento]

Hello,

gurmukh:
Always check the result.ErrorCode before using the location data in the callback. You will probably get some error code, when undefined is returned.

LWCARAB:
You should init the code somehow. Like:

test.location.init();
test.location.getLocation(
  function(response){ alert(response.success); }, 
  function(response){ alert(response.error); }
);

Br,
Ilkka

[gurmukh]

Hi there

I managed to fix it by just re-calling the function to get the Location if it was "undefined". That seems to do the trick.

Changing the cache value, the timeout value etc made no difference.

I also noticed that the JS was causing the browser to crash under certain situations so had to re-jig the whole thing.

Trial and error :-)!