Falling Snow for Flash CS4/AS3 - Page 2
       by kirupa  |  8 December 2009

In the previous page, you setup your stage and created the Snowflake movie clip. In this page, let's create the class file the movie clip will refer to.

Creating the Snowflake Class File
Ok, let's create this class file once and get it over with:

1. From inside Flash CS4, go to File | New to display the New Document dialog.
2. Once the New Document dialog has been launched, select ActionScript File from the list of document types listed:

[ create a new ActionScript File ]

3. With the ActionScript File type selected, click OK to create the new file. The New Document window will disappear and you will see the class file created and opened for you:

[ the blank code editor represents your class file ]

4. This ActionScript file doesn't actually live on your disk yet. It is just something that you see in Flash, so let's make it permanent by saving it. Go to File | Save to launch the Save As dialog. Browse to the directory your current Flash (FLA) file is in and give your file the name Snowflake:

[ gives this class file the name Snowflake - with the capital 'S' ]

Note, it is extremely important that you save your Snowflake ActionScript file in the same directory your Flash source file is in. For example, here is my directory where the FLA file and the AS file are stored:

[ the FLA and the AS file are in the same folder - such a happy family ]

5. Go back into Flash and make sure your Snowflake AS file is currently open for editing. Right now, it is just a blank document with nothing in it. Let's go ahead and add the code that makes it all work.
   
   Copy and paste the following code into your Snowflake AS file:

package

{

import flash.display.*;

import flash.events.*;

 

public class Snowflake extends MovieClip

{

private var xPos:Number = 0;

private var yPos:Number = 0;

 

private var xSpeed:Number = 0;

private var ySpeed:Number = 0;

 

private var radius:Number = 0;

 

private var scale:Number = 0;

private var alphaValue:Number = 0;

 

private var maxHeight:Number = 0;

private var maxWidth:Number = 0;

 

public function Snowflake()

{

SetInitialProperties();

}

 

public function SetInitialProperties()

{

//Setting the various parameters that need tweaking

xSpeed = .05 + Math.random()*.1;

ySpeed = .1 + Math.random()*3;

radius = .1 + Math.random()*2;

scale = .01 + Math.random();

alphaValue = .1 + Math.random();

 

var stageObject:Stage = this.stage as Stage;

maxWidth = stageObject.stageWidth;

maxHeight = stageObject.stageHeight;

 

this.x = Math.random()*maxWidth;

this.y = Math.random()*maxHeight;

 

xPos = this.x;

yPos = this.y;

 

this.scaleX = this.scaleY = scale;

this.alpha = alphaValue;

 

this.addEventListener(Event.ENTER_FRAME, MoveSnowFlake);

}

 

function MoveSnowFlake(e:Event)

{

xPos += xSpeed;

yPos += ySpeed;

 

this.x += radius*Math.cos(xPos);

this.y += ySpeed;

 

if (this.y - this.height > maxHeight)

{

this.y = -10 - this.height;

this.x = Math.random()*maxWidth;

}

}

}

}

6. If you save your class file and test your movie out, you'll see your lone little snowflake slowly oscillating its way down.

Wow, you covered quite a bit of ground this page. All of this has basically allowed you to have one snowflake fall. Don't worry, there is more, so let's look at how to turn your single snowflake into a mild winder storm on the next page.

Onwards to the next page!

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