BlackBerry Tablet Applications : Exploring the APIs - GPS

GPS stands for Global Positioning System. GPS is a space-based satellite navigation system that sends reliable location information to your handheld device.

If your application requires the use of the device’s GPS capabilities, you will need to select the read_geolocation permission when creating your project. 

Let’s review the code that follows. First, you’ll notice that there is a private variable named geoLocation declared of type flash.sensors.GeoLocation. Within applicationComplete of the application, an event handler function is called; it first checks to see if the device has an available GPS unit by reading the static property of the GeoLocation class. If this property returns as true, a new instance of GeoLocation is created and the data refresh interval is set to 500 milliseconds (.5 seconds) within the setRequestedUpdateInterval method, and an event listener of type GeoLocationEvent.UPDATE is added to handle updates. Upon update, the GPS information is read from the event and written to a TextArea within the handleUpdate function. Note that there is also some math being done to convert the speed property into miles per hour and kilometers per hour. The results can be seen within Figure 1.

<?xml version="1.0" encoding="utf-8"?>
<s:Application xmlns:fx="http://ns.adobe.com/mxml/2009"
               xmlns:s="library://ns.adobe.com/flex/spark"
               applicationComplete="application1_applicationCompleteHandler(event)">
    <fx:Script>
        <![CDATA[
            import mx.events.FlexEvent;

            import flash.sensors.Geolocation;

            private var geoLocation:Geolocation;

            protected function application1_applicationCompleteHandler
            (event:FlexEvent):void {
                if(Geolocation.isSupported==true){
                    geoLocation = new Geolocation();
                    geoLocation.setRequestedUpdateInterval(500);
                    geoLocation.addEventListener(GeolocationEvent.UPDATE, 
                    handleLocationRequest);
                } else {
                    status.text = "Geolocation feature not supported";
                }
            }

            private function handleLocationRequest(event:GeolocationEvent):void {
                var mph:Number = event.speed*2.23693629;
                var kph:Number = event.speed*3.6;
                info.text = "Updated: " + new Date().toTimeString() + "\n\n"
                    + "latitude: " + event.latitude.toString() + "\n"
                    + "longitude: " + event.longitude.toString() + "\n"
                    + "altitude: " + event.altitude.toString()  + "\n"
                    + "speed: " + event.speed.toString()  + "\n"
                    + "speed: " + mph.toString()  + " MPH \n"
                    + "speed: " + kph.toString()  + " KPH \n"
                    + "heading: " + event.heading.toString()  + "\n"
                    + "horizontal accuracy: "
                    + event.horizontalAccuracy.toString()  + "\n"
                    + "vertical accuracy: "
                    + event.verticalAccuracy.toString();
            }

        ]]>
    </fx:Script>
    <fx:Declarations>
        <!-- Place non-visual elements (e.g., services, value objects) here -->
    </fx:Declarations>

    <s:Label id="status" text="Geolocation Info" top="10" width="100%" 
textAlign="center"/>
    <s:TextArea id="info" width="100%" top="40" editable="false"/>
</s:Application>