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Revision as of 19:01, 24 April 2013 by jasfox (Talk | contribs)

HERE Maps API - Coroutines

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This article demonstrates the use of HERE Maps API Coroutine feature.

Article Metadata
Tested with
Devices(s): Internet Explorer, Google Chrome, Firefox, Opera
Compatibility
Platform(s): Web browser
Dependencies: HERE Maps 2.2.4
Article
Keywords: HERE Maps, JavaScript, coroutines
Created: Maveric (28 Jun 2011)
Updated: avnee.nathani (31 Dec 2011)
Last edited: jasfox (24 Apr 2013)


Introduction and Prerequisites

Firstly, please read the complete section of Coroutines at the HERE Maps API reference. It is explained there in detail, and here is the direct link:

http://developer.here.net/docs/maps_js/topics_api_pub/nokia.maps.util.Coroutine.html

The example below is using the same concept as in the How to pan the map example.

As the Coroutine built in serves a similar function to the JavaScript setTimeout() and setInterval(), you can also utilize them in same type of use cases. The main idea behind the Coroutine implementation is to serve as a point of saving some CPU time cycles, while performing multiple tasks during the same mapping program - threading.

Because there is a lot to this subject, it is highly recommended that you read the related API chapter.

Example code

This example will loop from 1 to 500 with 10ms delay. The run is displayed on screen, and after the set time period of Coroutine operations, the map will pan to a new position and the Coroutines get terminated. Remember to add in your own AppId and Token.

<!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>Coroutines Example</title>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8" />
<script type="text/javascript"
src="http://api.maps.nokia.com/2.2.4/jsl.js" charset="utf-8">
</script>
</head>
<!--Add the all_is_ready function to the onload event if code does not work in IE -->
<body onload = "all_is_ready()">
<div id="showCoords" style="height: 2.0em; font-size: 2em; color: blue;"></div>
 
<div id="map" style="width:80%; height:80%; position: absolute; "></div>
 
<script type="text/javascript">
/////////////////////////////////////////////////////////////////////////////////////
// Don't forget to set your API credentials
//
// Replace with your appId and token which you can obtain when you
// register on http://api.developer.nokia.com/
//
nokia.Settings.set( "appId", "YOUR APP ID GOES HERE");
nokia.Settings.set( "authenticationToken", "YOUR AUTHENTICATION TOKEN GOES HERE");
 
//
/////////////////////////////////////////////////////////////////////////////////////
 
var myInterval = 0;
var myTimer;
var map_start_x = 100;
var map_start_y = 100;
var map_end_x = 120;
var map_end_y = 100;
var myMap;
 
//If code does not work in IE, make sure the following code is commented out
/*if (document.addEventListener)
document.addEventListener("DOMContentLoaded", all_is_ready, false);*/

 
 
 
function all_is_ready(){
 
alert("Click OK to start the panning using Coroutine");
 
myMap = new nokia.maps.map.Display(document.getElementById("map"),
{
components: [ new nokia.maps.map.component.Behavior(),
new nokia.maps.map.component.ZoomBar(),
new nokia.maps.map.component.Overview(),
new nokia.maps.map.component.TypeSelector(),
new nokia.maps.map.component.ScaleBar() ],
zoomLevel: 3,
center: [52.51, 13.4]
 
});
 
 
var i = 0,
Coroutine = nokia.maps.util.Coroutine;
 
// Define the 1st coroutine - increase the value of i by one every 10 milliseconds, until we reach a 100.
// Watch the console output for the numbers!
 
var iteration = Coroutine.create("iterator", function( scope, context ) {
i++;
 
if ( i <= 500 ) {
document.getElementById("showCoords").innerHTML = "Wait until 500 to see the map move! : "+i+"/500";
return Coroutine.sleep(10);
}
 
map_start_x = map_start_x + 200;
map_start_y = map_start_y + 200;
map_end_x = map_end_x - 400;
map_end_y = map_end_y + 400;
 
// pan the map to the new position after the loop is over
myMap.pan(map_start_x, map_start_y, map_end_x, map_end_y);
 
});
 
// 2nd coroutine display iteration in console.log every 100 miliseconds
var printing = Coroutine.create("printing", function( scope, context ) {
console.log(i);
 
return Coroutine.sleep(100);
});
 
// 1st coroutine, init to the "coroutine" variable
var coroutine = iteration();
 
// 2nd second coroutine, init to the "coroutine2" variable
var coroutine2 = printing();
 
// Add an observer to the 1st coroutine for it's status
coroutine.addObserver("status", function( context, key, value, oldValue ) {
if ( value == Coroutine.TERMINATED ) { // When gets terminated
Coroutine.kill( coroutine2 ); // kill the 2nd coroutine
document.getElementById("showCoords").innerHTML = "Coroutine finished, and got terminated.";
}
});
 
}
</script>
</body>
</html>

For more on the HERE Maps API

Please check out the HERE Maps API full documentation and API reference here:

You may also access the interactive API explorer

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