Emanuele Feronato

Talking about Actionscript 3, Flash and Game development.

Old readers should remember Flash game creation tutorial – part 1… it’s an ond AS2 tutorial about the creation of a game like Ball Revamped and its sequels.

Later Tim Edelaar coded it into AS3 in Step by step AS3 translation of Flash game creation tutorial – part 1, but with the whole code in a single class, and now it’s time for me to release the AS3 version of the tutorial using classes.

We are going to use three actionscript files: as3circle.as for the game, circle.as for the hero (the ball) and keys.as for keyboard input.

keys.as is the same class used in Introduction to AS3 classes so you can understand the importance of writing classes: I won’t have to worry for keyboard input anymore (well… as long as I am using arrows and space keys)

How to link classes

Linking classes is very important in AS3, that’s how you should manage class linking:

This is the movie properties panel:

Writing as3circle in the Document class field will set as3circle.as as the main class file.

This is the circle object properties panel:

Writing circle in the Class field will set circle.as as the class file for the circle object.

Now your .fla file and the three .as files must be in the same path.

And this is the code for every file… I don’t think there is any need to comment it because it was already commented in dozens of posts… anyway if you need comments, just ask for them in… the comments.

as3circle.as file:

package {
	import flash.display.Sprite;
	import flash.events.Event;
	public class as3circle extends Sprite {
		public var keyboard_input:keys;
		public var circle_hero = new circle;
		public function as3circle() {
			addChild(circle_hero);
			circle_hero.init();
			var keyboard_sprite = new Sprite();
			addChild(keyboard_sprite);
			keyboard_input = new keys(keyboard_sprite);
			stage.addEventListener(Event.ENTER_FRAME,on_enter_frame);
		}
		public function on_enter_frame(event:Event) {
			if (keyboard_input.is_left()) {
				circle_hero.apply_force(-1,0);
			}
			if (keyboard_input.is_right()) {
				circle_hero.apply_force(1,0);
			}
			if (keyboard_input.is_up()) {
				circle_hero.apply_force(0,-1);
			}
			if (keyboard_input.is_down()) {
				circle_hero.apply_force(0,1);
			}
		}
	}
}

circle.as file:

package {
	import flash.display.Sprite;
	import flash.events.Event;
	public class circle extends Sprite {
		private var x_speed:Number;
		private var y_speed:Number;
		private var power:Number;
		private var friction:Number;
		private var gravity:Number;
		public function circle() {
			addEventListener(Event.ENTER_FRAME, movement);
		}
		private function movement(e:Event) {
			x+=x_speed;
			y+=y_speed;
			rotation += x_speed;
			y_speed += gravity;
			x_speed *= friction;
			y_speed *= friction;
			if (x>500 || x<0 ||  y >400 || y<0) {
				init();
			}
		}
		public function apply_force(x_force,y_force) {
			x_speed += (x_force*power);
			y_speed += (y_force*power);
		}
		public function init() {
			gravity = 0.1;
			power = 0.66;
			friction = 0.99;
			x_speed = 0;
			y_speed = 0;
			x = 250;
			y = 200;
		}
	}
}

keys.as file

package {
	import flash.events.KeyboardEvent;
	public class keys {
		private var press_left = false;
		private var press_right = false;
		private var press_up = false;
		private var press_down = false;
		private var press_space = false;
		public function keys(movieclip) {
			movieclip.stage.addEventListener(KeyboardEvent.KEY_DOWN, key_down);
			movieclip.stage.addEventListener(KeyboardEvent.KEY_UP, key_up);
		}
		public function is_left() {
			return press_left;
		}
		public function is_right() {
			return press_right;
		}
		public function is_up() {
			return press_up;
		}
		public function is_down() {
			return press_down;
		}
		public function is_space() {
			return press_space;
		}
		private function key_down(event:KeyboardEvent) {
			if (event.keyCode == 32) {
				press_space = true;
			}
			if (event.keyCode == 37) {
				press_left = true;
			}
			if (event.keyCode == 38) {
				press_up = true;
			}
			if (event.keyCode == 39) {
				press_right = true;
			}
			if (event.keyCode == 40) {
				press_down = true;
			}
		}
		private function key_up(event:KeyboardEvent) {
			if (event.keyCode == 32) {
				press_space = false;
			}
			if (event.keyCode == 37) {
				press_left = false;
			}
			if (event.keyCode == 38) {
				press_up = false;
			}
			if (event.keyCode == 39) {
				press_right = false;
			}
			if (event.keyCode == 40) {
				press_down = false;
			}
		}
	}
}

And we have our oooold game running in AS3 with classes.

Download the source code and enjoy.