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After you have pasted the above code, you have one more thing to do before you can test your app. Do you see the place in the code where I have said "Your Key Here"? Replace that string with either your API key or the sample one I provided:

ABQIAAAAwk8Uo9ZkiYLo0bvznt5qbxSIV5tnHDoabJrKPiVale6sm5IJBBS2C3Ww9LHmZUrLpe104a4FUKqH9g

Once you have replaced the API key text with the actual key itself, press Ctrl + Enter to see your app work:

All right. Now that you have a working app, let's quickly look at the code to see how this was all set up. In this article I will just describe the basics of how to have a map up and running with directions displayed.

Looking at the Code
Like all APIs, the Google Maps API is an abstraction - it provides a nice interface that hides the complexities that lie beneath. If you had to figure out a way to communicate with the Google Maps API from scratch, you may have to do a lot of tricky, complicated work. Thanks to this API, the tricky and complicated work has already been done for you. All you have to do is just code against the nice interface.

Let's look at the code that you have to write to talk to this API starting at the very top:

import com.google.maps.LatLng;

import com.google.maps.Map;

import com.google.maps.MapEvent;

import com.google.maps.MapType;

import com.google.maps.InfoWindowOptions;

import com.google.maps.LatLngBounds;

import com.google.maps.MapMoveEvent;

import com.google.maps.overlays.Marker;

import com.google.maps.overlays.MarkerOptions;

import com.google.maps.interfaces.IPolyline;

import com.google.maps.services.*;

These are import statements that point your code to the location where the various classes and types you are using live. Because a lot of the code you are using requires the Google Maps API, something which Flash doesn't know anything about by default, you have to explicitly point the compiler to the API via these import statements.

---

var dir:Directions;

var polyline:IPolyline;

var map:Map

There are three variables that I want globally accessible, so I am just declaring them. These variables will be initialized in later methods that I describe.

---

function setupMap() {

map = new Map();

map.key="Your Key Here";

map.setSize(new Point(400,400));

map.x=0;

map.y=0;

map.addEventListener(MapEvent.MAP_READY, onMapReady);

this.addChild(map);

}

setupMap();

The above code defines the setupMap method along with the method call that actually calls your setupMap method. The setupMap method does a few things. It initializes your map variable from earlier, sets your map's API key, specifies position/size, and sets up the event handler. The final thing you do is actually add your map to your application's visual tree. That is accomplished via the addChild method.

The format for binding your event to an event handler is consistent with everything you've done in the past. What may be new to you is the actual event itself. The Google Maps API declares its own custom event called MAP_READY that lives in the MapEvent class, and as I will show next, you will see the onMapReady event handler get called when the MAP_READY event gets called.

---

function onMapReady(event:Event):void {

dir = new Directions();

dir.addEventListener(DirectionsEvent.DIRECTIONS_SUCCESS,onDirectionsLoaded);

dir.load("645 Carlton Road, Markham, ON to Fawnbrook Circle, Markham, ON");

}

The onMapReady method is, as I showed a few seconds ago, is the event handler for the the MAP_READY event. When your map is ready, this event handler will get called, and this event handler is responsible for setting off the events that cause things to be drawn on your recently-made ready map.

I initialize the dir variable to a new Directions object, add another event handler to let me know when my direction is ready, and actually specify the addresses I want to find directions to. In other words, when the directions I specify as arguments to my dir object's load method get sent to the server and successfully returned, the onDirLoad gets called. Let's look at this onDirLoad method in greater detail next.

---

function onDirectionsLoaded(event:DirectionsEvent):void {

var returnedDirection:Directions=event.directions;

 

var startLatLng:LatLng=returnedDirection.getRoute(0).getStep(0).latLng;

var endLatLng:LatLng=returnedDirection.getRoute(returnedDirection.numRoutes-1).endLatLng;

 

polyline=returnedDirection.createPolyline();

 

// Remove everything from map and add back the markers and polyline

map.clearOverlays();

map.addOverlay(polyline);

map.addOverlay(new Marker(startLatLng));

map.addOverlay(new Marker(endLatLng));

map.setCenter(returnedDirection.bounds.getCenter(), map.getBoundsZoomLevel(returnedDirection.bounds));

}

The final method we will look at is the onDirectionsLoaded method that gets called when the server returns the direction data for the addresses you specified earlier.

This code is specific to the Google Maps API, so I am not going to be describing all of this in greater detail. What this code does is pretty straightforward. What you first do is get the latitudinal and longitudinal coordinates of your start and end point. This is responsible for setting your starting and ending points.

Once you have these points, you need to generate the path between them. Unfortunately, this isn't like drawing a straight or curved line between two points :P

The path that gets generated is actually a series of lines that snakes through various roads and intersections to get you between two points. The createPolyLine method found in your Directions object gets you exactly that - a series of lines that, when put together, create the lines between the two points.

The final step once all of the data has been calculated is to actually display them on your map. That is handled elegantly by the following five lines:

// Remove everything from map and add back the markers and polyline

map.clearOverlays();

map.addOverlay(polyline);

map.addOverlay(new Marker(startLatLng));

map.addOverlay(new Marker(endLatLng));

map.setCenter(returnedDirection.bounds.getCenter(), map.getBoundsZoomLevel(returnedDirection.bounds));

Let's run through this code quickly. First, clear anything on your map that you may not want to see. After that, add the overlays for your directions, starting point, and ending point. You have one more thing remaining before you can call it a day.

Your map's initial size is determined by two things. It is determined by your map's center point and the boundaries of the points that make up your starting point, ending point, and the path between them. Your map object's setCenter object takes those three inputs into account, does some magic, and sets up your map's center and zoom positions for you.

Conclusion
I hope this tutorial helped give you a leg up on using the Google Maps API to create a simple application. There is a lot more you can do, and this tutorial just scratched the surface of what is possible.

If you have any questions, please feel free to post on the forums, and I or others will help you out.

Cheers!

Gaurav Pandey