Using CreateJS with FlexJS

CreateJS is a JavaScript framework that makes use of the HTML5 Canvas, rather than the HTML DOM, to make graphic-based objects, such as shapes, buttons, and text. The integration of CreateJS with FlexJS lets CreateJS developers take advantage of coding in ActionScript (a cousin of JavaScript, with true classes and strong data typing). Further, CreateJS applications can use MXML for layout and definition.

Getting Started

The examples on this page require the installation of the Apache Flex SDK which can be found on the Getting Started With FlexJS page in order to run.

This section mimics the tutorial found on the Getting Started Guide on the CreateJS site. The example below uses a command line approach and can easily be adapted to a FlexJS-compatible IDE. 

Using EaselJS

Create a new directory for your FlexJS project and in that directory create a file called, Demo.mxml. Open the file and add the following Application tag and content:

<cjs:Application xmlns:fx="http://ns.adobe.com/mxml/2009"
                   xmlns:js="library://ns.apache.org/flexjs/basic" 
                   xmlns:cjs="library://ns.apache.org/flexjs/createjs"
                   >    
    <js:valuesImpl>
        <js:SimpleCSSValuesImpl />
    </js:valuesImpl>
    <js:initialView>
        <cjs:View>
        </cjs:View>
    </js:initialView>
</cjs:Application>

Notice that the namespace for the Application tag is cjs and the cjs namespace is defined to bring in all of the FlexJS CreateJS component framework. You will identify FlexJS CreateJS elements using the cjs namespace. The FlexJS CreateJS Application tag creates the HTML5 Canvas automatically.

Within the cjs:View element, add the following MXML tags to create a CreateJS circle.

    <cjs:Circle id="circle" x="100" y="100" width="100" height="100">
		<js:fill>
			<js:SolidColor color="#26C9FF" />
		</js:fill>
	</cjs:Circle>

Save the file and compile it. Open bin/js-debug/index.html in a browser. You should see a blue circle.

Using TweenJS

Continue with the previous example where you already have a circle to work with. You will add some MXML declarations for the tweens and a bit of ActionScript code to trigger them. Copy the following MXML declarations and Script block into the Demo.mxml file, above the js:initialView definition:

    <js:beads>
        <js:ApplicationDataBinding />
    </js:beads>
    
    <fx:Declarations>
    	<cjs:Sequence id="seq" target="circle" loop="true">
			<cjs:Tween id="tween1" target="circle" xTo="400" duration="1000" easing="{Ease.getPowInOut(4)}" /> 
			<cjs:Tween id="tween2" target="circle" alphaTo="0" yTo="175" duration="500" easing="{Ease.getPowInOut(2)}" />
			<cjs:Tween id="tween3" target="circle" alphaTo="0" yTo="225" duration="100" />
			<cjs:Tween id="tween4" target="circle" alphaTo="1" yTo="200" duration="500" easing="{Ease.getPowInOut(2)}" />
			<cjs:Tween id="tween5" target="circle" xTo="100" duration="800" easing="{Ease.getPowInOut(2)}" />
    	</cjs:Sequence>
    </fx:Declarations>
    
    <fx:Script>
    	<![CDATA[
			// the import is required by the Ease functions in the data binding
    		import org.apache.flex.createjs.tween.Ease;
    	]]>
    </fx:Script>

The fx:Declarations tag in MXML is where you put non-visual items that are referenced in the app. Here, a set of Tweens is declared for the circle and surrounded by the Sequence tween which forces the individual Tweens to play in the order specified. Note that the easing function on some of the Tweens is specified using binding to an expression.

In order for the Sequence to happen however, the Sequence's play() function, needs to be triggered by an event. Modify the cjs:Application tag with an applicationComplete event handler to call the play() function:

          applicationComplete="seq.play()">

Save the file and compile it. Open the bin/js-debug/index.html file in a browser. You will see the circle move and fade across the screen. The loop option on the Sequence will make it run continuously.

You can see the complete code below.

Comparison

This section examines the demonstration code (above) in more detail and compares it with the original CreateJS demo code. To see this, there is a CreateJS example (see Getting Started Guide) that demonstrates how to use EaselJS to display a circle. The example looks like this:

<html>
  <head>
    <script src="https://code.createjs.com/createjs-2015.11.26.min.js"></script>
    <script>      
      function init() {
        var stage = new createjs.Stage("demoCanvas");
        var circle = new createjs.Shape();
        circle.graphics.beginFill("DeepSkyBlue").drawCircle(0, 0, 50);
        circle.x = 100;
        circle.y = 100;
        stage.addChild(circle);
        stage.update();
      }
    </script>
  </head>
  <body onload="init();">
    <canvas id="demoCanvas" width="500" height="200"></canvas>
  </body>
</html>

  The corresponding FlexJS MXML file looks like this:

<cjs:Application xmlns:fx="http://ns.adobe.com/mxml/2009"
                   xmlns:js="library://ns.apache.org/flexjs/basic" 
                   xmlns:cjs="library://ns.apache.org/flexjs/createjs"
                   >
    <js:valuesImpl>
        <js:SimpleCSSValuesImpl />
    </js:valuesImpl>
    <js:initialView>
        <cjs:View>
			<cjs:Circle id="circle" x="100" y="100" width="100" height="100">
				<js:fill>
					<js:SolidColor color="#26C9FF" />
				</js:fill>
			</cjs:Circle>
   		    
        </cjs:View>
    </js:initialView>
</cjs:Application>

Beneath the covers, the FlexJS application creates an HTML5 Canvas and sets up the drawing Stage; FlexJS has wrapper classes for the CreateJS and EaselJS constructs (note that today only a few exist but the pattern to add more has been established). Using either ActionScript or MXML, the CreateJS components can be added to the stage and displayed. In the example above, a CreateJS Circle is created using an MXML tag and specifying a fill color (a stroke can also be used to give the circle an outline). 

In addition to EaselJS, the FlexJS CreateJS framework also includes a bit of TweenJS, the animation package. There is a small TweenJS example on the CreateJS page which looks like this:

<html>
  <head>
    <script src="https://code.createjs.com/createjs-2015.11.26.min.js"></script>
    <script>
      function init() {
        var stage = new createjs.Stage("demoCanvas");
        var circle = new createjs.Shape();
        circle.graphics.beginFill("Crimson").drawCircle(0, 0, 50);
        circle.x = 100;
        circle.y = 100;
        stage.addChild(circle);
        createjs.Tween.get(circle, {loop: true})
          .to({x: 400}, 1000, createjs.Ease.getPowInOut(4))
          .to({alpha: 0, y: 75}, 500, createjs.Ease.getPowInOut(2))
          .to({alpha: 0, y: 125}, 100)
          .to({alpha: 1, y: 100}, 500, createjs.Ease.getPowInOut(2))
          .to({x: 100}, 800, createjs.Ease.getPowInOut(2));
        createjs.Ticker.setFPS(60);
        createjs.Ticker.addEventListener("tick", stage);
      }
    </script>
  </head>
  <body onload="init();">
    <canvas id="demoCanvas" width="500" height="200"></canvas>
  </body>
</html>

The corresponding FlexJS MXML file looks like this:

<cjs:Application xmlns:fx="http://ns.adobe.com/mxml/2009"
                   xmlns:local="*"
                   xmlns:js="library://ns.apache.org/flexjs/basic" 
                   xmlns:cjs="library://ns.apache.org/flexjs/createjs"
                   applicationComplete="runEffect()"
                   >
    <js:valuesImpl>
        <js:SimpleCSSValuesImpl />
    </js:valuesImpl>
    
    <js:beads>
        <js:ApplicationDataBinding />
    </js:beads>
    
    <fx:Declarations>
    	<cjs:Sequence id="seq" target="circle" loop="true">
			<cjs:Tween id="tween1" target="circle" xTo="400" duration="1000" easing="{Ease.getPowInOut(4)}" /> 
			<cjs:Tween id="tween2" target="circle" alphaTo="0" yTo="175" duration="500" easing="{Ease.getPowInOut(2)}" />
			<cjs:Tween id="tween3" target="circle" alphaTo="0" yTo="225" duration="100" />
			<cjs:Tween id="tween4" target="circle" alphaTo="1" yTo="200" duration="500" easing="{Ease.getPowInOut(2)}" />
			<cjs:Tween id="tween5" target="circle" xTo="100" duration="800" easing="{Ease.getPowInOut(2)}" />
    	</cjs:Sequence>
    </fx:Declarations>
    
    <fx:Script>
    	<![CDATA[
    		import org.apache.flex.createjs.tween.Ease;
    		
    		private function runEffect():void {    			
    			// run the sequence of tweens
    			seq.play();
    		}
    	]]>
    </fx:Script>
    
    <js:initialView>
        <cjs:View>
			<cjs:Circle id="circle" x="100" y="100" width="100" height="100">
				<js:fill>
					<js:SolidColor color="#26C9FF" />
				</js:fill>
			</cjs:Circle>
   		    
        </cjs:View>
    </js:initialView>
</cjs:Application>

The Tweens are declared in an fx:Declarations block and correspond to the CreateJS "tween.to()" functions. You specify exactly the same things: target, duration, x position, y position, alpha value, and even easing functions. An event handler triggers the sequence of Tweens to run. 

FlexJS is a "pay as you go" system. The use of binding for the easing functions on the Tweens, necessitates the including of the ApplicationDataBinding bead. With the bead the data binding will not happen and should only be included in applications that use data binding to reduce their final footprint and runtime overhead.

Extending FlexJS CreateJS

At this time the FlexJS CreateJS framework is far from complete. CreateJS has a lot to offer and this foray into it via FlexJS just touches upon it and lays the foundation to extend it.

Components from the FlexJS Basic framework cannot be used with components from the FlexJS CreateJS framework. This is due to the fact that CreateJS uses the HTML5 Canvas as its drawing space and maintains its own DOM; the FlexJS Basic framework uses the HTML DOM.

If you look at the flex-asjs repository, specifically the frameworks/projects/CreateJS directory, you'll see how the  FlexJS wrapper classes are composed. There is an Application class which provides the injection of the necessary CreateJS JavaScript downloads as well as creating the Canvas and the CreateJS Stage object.

From there, components use org.apache.flex.createjs.core.CreateJSBase as their foundation class. Other "higher level" components such as Circle, Rect, Label, and TextButton build from there. The key part is the createElement function. You can see how the CheckBox, for example, is composed from several different EaselJS elements. You would add any new components following this pattern.

Since CreateJS is an JavaScript-only framework, you can see that much of the classes use the COMPILE::JS compiler tag to identify the code that only belongs on the JavaScript side (code that gets cross-compiled to JavaScript and does not have any relevance to the SWF). Any additional CreateJS structures or code should be wrapped in the COMPILE::JS tag.

Further, there must be an SWF-side presence in order for the components to be usable in ActionScript within a client application or even as MXML tags. In some cases you will see COMPILE::AS3 code blocks that are just empty or return NULL or use an existing equivalent. Extending the FlexJS CreateJS requires you to think on both sides.

Finally, once components are added, if they can be used from MXML, they must appear in the creates-manifest.xml file. Classes should also appear in the CreateJSClasses.as file if they are not MXML components and can be used from ActionScript and need to be in the SWF.