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The CREATION_COMPLETE event handler
The code in the constructor in Listing 3 registers a CREATION_COMPLETE event handler on the Canvas object. You are already familiar with the use of event handlers of this type.
The CREATION_COMPLETE event handler is shown in its entirety in Listing 4. As before, there is nothing in Listing 4 that I haven't explained in previouslessons, so no explanation beyond the embedded comments should be needed.
//This handler method is executed when the Canvas has
// been fully created.private function creationCompleteHandler(
event:mx.events.FlexEvent):void{//Set the width and height of the Canvas object// based on the size of the bitmap in the
// normalSky image.this.width = Bitmap(normalSky.content).width;
this.height = Bitmap(normalSky.content).height;//Add the images to the Canvas object. Note that// the two images are overlaid at 0,0.
this.addChild(normalSky);this.addChild(flippedSky);//Add a button in the upper-left corner in front
// of the sky images and register a CLICK event// handler on the button.
button = new Button();button.x = 10;
button.y = 10;button.addEventListener(MouseEvent.CLICK, onClick);
button.label = "Click Me";button.setStyle("color", 0xFFFF00);
addChild(button);//Get and save a reference to a Bitmap object
// containing the contents of the tree file.treeBitMap = Bitmap(tree.content);//Place the treeBitMap in a new Image object and
// place it on the canvas near the bottom center of// the canvas.
treeBitMap.x =canvasObj.width / 2 - treeBitMap.width/2;treeBitMap.y = canvasObj.height - treeBitMap.height;
newTreeImage.addChild(treeBitMap);this.addChild(newTreeImage);//Make the tree almost invisible. It will be made
// highly visible in conjunction with a// lightening flash.
newTreeImage.alpha = 0.2;//Cause the blue background of the tree to// be transparent.
processChromaKey(treeBitMap);//Register a timer listener and start the timer// running.
timer.addEventListener(TimerEvent.TIMER, onTimer);timer.start();
} //end creationCompleteHandler Beginning of the TIMER event handler
The last two statements in Listing 4 register a TIMER event listener on the Timer object that was instantiated in Listing 1 and start the timer running.
The TIMER event handler begins in Listing 5. There is some interesting new code in this method, so I will break it down and explain it infragments.
//TimerEvent handler. This method is executed each
// time the timer object fires an event.public function onTimer(event:TimerEvent):void {//Update the loop counter. Several things depend on
// this counter.loopCntr++;
if (loopCntr>int.MAX_VALUE-2) {
//Guard against numeric overflow.loopCntr = 0;
}//end if//Play a wind sound every 100th timer event only// if a random value is greater than 0.5. This
// should happen half the time on the average.if ((loopCntr % 100 == 0)&&(Math.random()>0.5)) {
wind.play();}//end if//Make random changes to the background color.
processBackgroundColor();//Make changes to the alpha values of the normal// and flipped sky images.
makeTheCloudsMove(); 
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