Archive for the ‘actionscript’ tag
Flex and JavaScript
I’m currently working on a Web application project that is primarily coded in JavaScript. As part of the project however, I needed to use a Flex component for part of the application. I would also need a series of components (search boxes, trees and grids) to interact with this component. At first, it seemed to make sense to do all of this in Flex. However, when it comes to client-side development, we’re primarily a JavaScript shop, and would prefer to keep the amount of Flex we write to a minimum. Also, from a styling perspective, our existing JavaScript components would fit in better with our overall application, so it made much more sense for us to use them rather than Flex’s trees, grids and so on. Of course, this raised a problem – how do we communicate between JavaScript and Flex?
Fortunately, this is actually very straightforward. To prove the concept, I decided to write up a basic application that would allow you to pass messages between Flex and JavaScript components and output them on the screen. Here is a screenshot of this application in action (click for a larger image):
Sample Project in action
So on the left hand side of the application, there is a standard HTML input field, button element and a read-only textarea element. The input field will allow the user to write a message to be passed to the Flex application, which gets sent when the user clicks the “Send to Flex” button. The textarea field will be updated with any messages that are sent to JavaScript by Flex. On the right-hand-side, you have the same thing, but this time it will allow you to enter a message to send to JavaScript from Flex, and has an area where messages sent by JavaScript to Flex will be shown.
Let’s walk through how I did this. It’s worth pointing out at this point that I used Flash Builder 4 and the Flex 4 SDK to create this application. If you have a different setup, you may need to change your code to suit your version.
In Flash Builder, create a new Flex Project, and call it TestJSFlex. Let’s start off with the Flex application interface. You can use the Design view if you wish, but for a simple application like this, it’s fairly straightforward to create everything in code. Just before the closing </s:Application> tag in your source code, add the following three lines of code:
<s:TextInput x="2" y="2" width="310" id="flexInput"/> <s:Button x="320" y="3" width="100" label="Send to JS" /> <s:TextArea x="2" y="32" width="416" height="200" id="flexMessages" editable="false"/>
While you’re at it, add the following attributes to your opening <s:Application> element:
width="440" height="255"
That’s our Flex application user interface done. Pretty simple, huh? Next, let’s change the HTML template that Flash Builder produces to add some basic HTML elements for the JavaScript side of our application to use. In “Package Explorer” (usually at the top left hand side of Flash Builder), your project folder should contain a few subfolders: src, Flex 4.0, bin-debug, html-template and libs. Expand the html-template folder and you should see a file named index.template.html. Right-click this file, and from the context menu select “Open With -> Text Editor”. The file should now open in a new editor tab in the main part of the IDE. In this file, locate the following section of HTML code:
<div id="flashContent">
<p>
To view this page ensure that Adobe Flash Player version
${version_major}.${version_minor}.${version_revision} or greater is installed.
</p>
<script type="text/javascript">
var pageHost = ((document.location.protocol == "https:") ? "https://" :Â "http://");
document.write("<a href='http://www.adobe.com/go/getflashplayer'><img src='"
+ pageHost + "www.adobe.com/images/shared/download_buttons/get_flash_player.gif' alt='Get Adobe Flash player' /></a>" );
</script>
</div>
This is basically the element where the Flex application will appear on the HTML page. We’re going to wrap it in a <div> container and add a section before it with a HTML form:
<div id="container">
<h1>Flex and JavaScript</h1>
<div class="section">
<h2>JavaScript:</h2>
<input type="text" id="js_value" />
<input type="button" id="js_button" value="Send to Flex" />
<br />
<textarea id="js_messages" readonly></textarea>
</div>
<div class="section clearfix">
<h2>Flex:</h2>
<div id="flashContent">
<p>
To view this page ensure that Adobe Flash Player version
${version_major}.${version_minor}.${version_revision} or greater is installed.
</p>
<script type="text/javascript">
var pageHost = ((document.location.protocol == "https:") ? "https://" :Â Â Â "http://");
document.write("<a href='http://www.adobe.com/go/getflashplayer'><img src='"
+ pageHost + "www.adobe.com/images/shared/download_buttons/get_flash_player.gif' alt='Get Adobe Flash player' /></a>" );
</script>
</div>
</div>
</div>
In the code above, we have added a few HTML form elements: a text field with the ID js_value, a button with the ID js_button and a read-only textarea with the ID js_messages. To make the whole thing look right, we’re going to add some CSS properties which will define the layout and size of the elements. In index.template.html, locate the CSS section of the code near the top of the file, which by default should contain:
<style type="text/css" media="screen">
html, body { height:100%; }
body { margin:0; padding:0; overflow:auto; text-align:center; background-color: ${bgcolor}; }
#container { width: 900px; margin: 0px auto; text-align: left; }
#flashContent { display:none; }
</style>
Modify this so that it contains:
<style type="text/css" media="screen">
html, body { height:100%; }
body { margin:0; padding:0; overflow:auto; text-align:center; background-color: ${bgcolor}; }
#container { width: 900px; margin: 0px auto; text-align: left; }
#flashContent { display:none; }
h1, h2 { font-family: Helvetica, Arial, sans-serif; }
h2 { margin-top: 0px; }
.section { width: 450px; float: left; }
.clearfix:after {
content: ".";
display: block;
height: 0;
clear: both;
visibility: hidden;
}
#js_value { width: 310px; }
#js_button { width: 100px; }
#js_messages { width: 416px; height: 195px; margin-top: 8px; }
</style>
The CSS properties should be fairly self-explanatory. Basically, we have a container div 900 pixels wide, with two 450px sections inside it that appear side by side (using the float property), with a clearfix put in place so everything looks right in older browsers (just a note – I haven’t checked if this looks OK in anything other than Firefox 3.6, so don’t flame me if it doesn’t). Finally, we add some widths and heights to the form fields so they match up nicely with the Flex components.
That’s the UI section of the application taken care of. Next, let’s actually make Flex and JavaScript talk to each other. First, let’s get Flex talking to JavaScript. In the TestJSFlex.mxml file, just above where you entered the <s:TextInput> and other components a while back, add the following code:
<fx:Script>
<![CDATA[
public function sendToJS():void {
ExternalInterface.call("receiveFromFlex", flexInput.text);
}
]]>
</fx:Script>
This script block simply defines a single function named sendToJS. This function uses the ExternalInterface.call function to call a JavaScript function. The first parameter here is the name of the JavaScript function you want to call, in our case receiveFromFlex, and this is followed by any parameters you want to pass to JavaScript. Here, we have simply passed the current value of the text property of our text box with the id flexInput. Next, find the following line of code near the bottom of TestJSFlex.mxml:
<s:Button x="320" y="3" width="100" label="Send to JS" />
Let’s add a click event handler to this button, which will call the sendToJS function any time a user presses the button:
<s:Button x="320" y="3" width="100" label="Send to JS" click="sendToJS()" />
That’s everything that we need to do on the Flex side to call a JavaScript function. Of course, this is pretty much useless unless we actually declare the JavaScript function it is trying to call, so let’s hop over to index.template.html and create that now. Just before the closing </head> tag in this file, add the following code:
<script type="text/javascript">
function receiveFromFlex(str) {
var msgs = document.getElementById("js_messages");
msgs.value += 'Flex says: '+str+'\n';
}
</script>
This function simply accepts a string value as a parameter, and appends it (followed by a new line) to the element with the ID js_messages (the textarea element). Save all your files and run the application by pressing the green Play/Run button in the Flash Builder toolbar. At this point, you should be able to enter a message in the input box on the right hand side (the Flex side) and hit “Send to JS”. This message should then appear on the left hand side. That was pretty easy, huh? Ok, now all that’s left for us to do is implement the reverse scenario – sending messages from JavaScript to Flex.
In the previous section, you created a <script> block in the index.template.html file. Inside this block, just below the receiveFromFlex function, add the following code:
function sendToFlex() {
var flexApp = document.getElementById("${application}");
flexApp.sendToFlex(document.getElementById("js_value").value);
}
window.onload = function() {
var btn = document.getElementById("js_button");
btn.onclick = sendToFlex;
}
The first function, sendToFlex, gets a handle to the Flex application object using document.getElementById. You’ll notice that the ${application} template variable is used. This is recommended so that if you change the name of your Flex application, you won’t need to change the value in your template file. The function then calls the sendToFlex function in the Flex application object. Finally, we attach this function as an event handler to the HTML button element with the ID js_button. That’s it on the JavaScript side of things. Save index.template.html and jump back to TestJSFlex.mxml. Now, let’s add the code necessary to handle this on the Flex side of things. Inside the <fx:Script> block, below the sendToJS function, add the following two functions:
public function initApp():void {
ExternalInterface.addCallback("sendToFlex", receiveFromJS);
}
public function receiveFromJS(str:String):void {
flexMessages.text += 'JS says: '+str+'\n';
}
The first function, initApp, uses the ExternalInterface.addCallback function to map a JavaScript function to a Flex function. Here, we tell the sendToFlex JavaScript function callback to execute the Flex function named receiveFromJS. This function accepts a String parameter and appends it to the <s:TextArea> element followed by a newline. The final piece of the puzzle is to wire up the initApp function to be called when the Flex application has finished loading. In your <s:Application> element, add the attribute
creationComplete="initApp()"
and you’re done! You can now run the application and enter messages in the HTML input field, which will appear in the Flex message box when you hit “Send to Flex”. Easy as pie! For reference purposes, here are the full listings for the two source files we’ve worked with in this post.
TestJSFlex.mxml:
<?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"
xmlns:mx="library://ns.adobe.com/flex/mx" width="440" height="255"
creationComplete="initApp()">
<fx:Declarations>
<!-- Place non-visual elements (e.g., services, value objects) here -->
</fx:Declarations>
<fx:Script>
<![CDATA[
public function sendToJS():void {
ExternalInterface.call("receiveFromFlex", flexInput.text);
}
public function initApp():void {
ExternalInterface.addCallback("sendToFlex", receiveFromJS);
}
public function receiveFromJS(str:String):void {
flexMessages.text += 'JS says: '+str+'\n';
}
]]>
</fx:Script>
<s:TextInput x="2" y="2" width="310" id="flexInput"/>
<s:Button x="320" y="3" width="100" label="Send to JS" click="sendToJS()" />
<s:TextArea x="2" y="32" width="416" height="200" id="flexMessages" editable="false"/>
</s:Application>
index.template.html:
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<!-- saved from url=(0014)about:internet -->
<html xmlns="http://www.w3.org/1999/xhtml" lang="en" xml:lang="en">
<!--
Smart developers always View Source.
This application was built using Adobe Flex, an open source framework
for building rich Internet applications that get delivered via the
Flash Player or to desktops via Adobe AIR.
Learn more about Flex at http://flex.org
// -->
<head>
<title>${title}</title>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<!-- Include CSS to eliminate any default margins/padding and set the height of the html element and
the body element to 100%, because Firefox, or any Gecko based browser, interprets percentage as
the percentage of the height of its parent container, which has to be set explicitly. Initially,
don't display flashContent div so it won't show if JavaScript disabled.
-->
<style type="text/css" media="screen">
html, body { height:100%; }
body { margin:0; padding:0; overflow:auto; text-align:center; background-color: ${bgcolor}; }
#container { width: 900px; margin: 0px auto; text-align: left; }
#flashContent { display:none; }
h1, h2 { font-family: Helvetica, Arial, sans-serif; }
h2 { margin-top: 0px; }
.section { width: 450px; float: left; }
.clearfix:after {
content: ".";
display: block;
height: 0;
clear: both;
visibility: hidden;
}
#js_value { width: 310px; }
#js_button { width: 100px; }
#js_messages { width: 416px; height: 195px; margin-top: 8px; }
</style>
<!-- Enable Browser History by replacing useBrowserHistory tokens with two hyphens -->
<!-- BEGIN Browser History required section ${useBrowserHistory}>
<link rel="stylesheet" type="text/css" href="history/history.css" />
<script type="text/javascript" src="history/history.js"></script>
<!${useBrowserHistory} END Browser History required section -->
<script type="text/javascript" src="swfobject.js"></script>
<script type="text/javascript">
<!-- For version detection, set to min. required Flash Player version, or 0 (or 0.0.0), for no version detection. -->
var swfVersionStr = "${version_major}.${version_minor}.${version_revision}";
<!-- To use express install, set to playerProductInstall.swf, otherwise the empty string. -->
var xiSwfUrlStr = "${expressInstallSwf}";
var flashvars = {};
var params = {};
params.quality = "high";
params.bgcolor = "${bgcolor}";
params.allowscriptaccess = "sameDomain";
params.allowfullscreen = "true";
var attributes = {};
attributes.id = "${application}";
attributes.name = "${application}";
attributes.align = "middle";
swfobject.embedSWF(
"${swf}.swf", "flashContent",
"${width}", "${height}",
swfVersionStr, xiSwfUrlStr,
flashvars, params, attributes);
<!-- JavaScript enabled so display the flashContent div in case it is not replaced with a swf object. -->
swfobject.createCSS("#flashContent", "display:block;text-align:left;");
</script>
<script type="text/javascript">
function receiveFromFlex(str) {
var msgs = document.getElementById("js_messages");
msgs.value += 'Flex says: '+str+'\n';
}
function sendToFlex() {
var flexApp = document.getElementById("${application}");
flexApp.sendToFlex(document.getElementById("js_value").value);
}
window.onload = function() {
var btn = document.getElementById("js_button");
btn.onclick = sendToFlex;
}
</script>
</head>
<body>
<!-- SWFObject's dynamic embed method replaces this alternative HTML content with Flash content when enough
JavaScript and Flash plug-in support is available. The div is initially hidden so that it doesn't show
when JavaScript is disabled.
-->
<div id="container">
<h1>Flex and JavaScript</h1>
<div class="section">
<h2>JavaScript:</h2>
<input type="text" id="js_value" />
<input type="button" id="js_button" value="Send to Flex" />
<br />
<textarea id="js_messages" readonly></textarea>
</div>
<div class="section clearfix">
<h2>Flex:</h2>
<div id="flashContent">
<p>
To view this page ensure that Adobe Flash Player version
${version_major}.${version_minor}.${version_revision} or greater is installed.
</p>
<script type="text/javascript">
var pageHost = ((document.location.protocol == "https:") ? "https://" :Â Â Â "http://");
document.write("<a href='http://www.adobe.com/go/getflashplayer'><img src='"
+ pageHost + "www.adobe.com/images/shared/download_buttons/get_flash_player.gif' alt='Get Adobe Flash player' /></a>" );
</script>
</div>
</div>
</div>
<noscript>
<object classid="clsid:D27CDB6E-AE6D-11cf-96B8-444553540000" width="${width}" height="${height}" id="${application}">
<param name="movie" value="${swf}.swf" />
<param name="quality" value="high" />
<param name="bgcolor" value="${bgcolor}" />
<param name="allowScriptAccess" value="sameDomain" />
<param name="allowFullScreen" value="true" />
<!--[if !IE]>-->
<object type="application/x-shockwave-flash" data="${swf}.swf" width="${width}" height="${height}">
<param name="quality" value="high" />
<param name="bgcolor" value="${bgcolor}" />
<param name="allowScriptAccess" value="sameDomain" />
<param name="allowFullScreen" value="true" />
<!--<![endif]-->
<!--[if gte IE 6]>-->
<p>
Either scripts and active content are not permitted to run or Adobe Flash Player version
${version_major}.${version_minor}.${version_revision} or greater is not installed.
</p>
<!--<![endif]-->
<a href="http://www.adobe.com/go/getflashplayer">
<img src="http://www.adobe.com/images/shared/download_buttons/get_flash_player.gif" alt="Get Adobe Flash Player" />
</a>
<!--[if !IE]>-->
</object>
<!--<![endif]-->
</object>
</noscript>
</body>
</html>
If you’d prefer to just take the sample Flex project, you can download a zip file of it below:
Facebook Gallery in Flex
In November 2008, a tutorial I wrote titled “Implement a Facebook photo album using the Flex SDK” was published on IBM’s developerWorks website. The tutorial begins by introducing the Facebook platform and explaining how a Facebook application is created. It then moves on to the open source Flex SDK and the MXML markup language and ActionScript scripting language that are used to develop Flex applications. At this point, a simple Flex application is created to introduce the reader to the development and deployment of Flex applications. After this, the tutorial shows the user how to create a feature-rich photo slideshow (with transitions and controls) that uses the reader’s Facebook photos and is deployed to their Facebook profile.
The following is the description of the tutorial on the IBM developerWorks website itself:
Adobe® has released the free, open source Flex SDK framework to enable developers to create Rich Internet Applications (RIAs). The Flex framework provides you with a method of creating cross-browser, cross-platform Web applications that is quick and simple. Flex applications run in the Flash player, which is installed on the majority of Internet-connected computers, but Flex also provides you with an object-oriented user interface framework similar to Javaâ„¢ Swing. In this tutorial, develop a Facebook application in Adobe Flex that displays a slideshow of a user’s Facebook photo albums. The Facebook application will contain a profile box listing all of the user’s photo albums, each a link to a Flex slideshow of that album. The Flex application will use the Facebook REST API to fetch the photos of the selected Facebook album and dynamically generate the slideshow.
Read the tutorial at http://www.ibm.com/developerworks/edu/wa-dw-wa-facebookflex.html
