Adding Weapons to Your Game: Flex & Actionscript Tutorial

At this point in the series we have implemented enough underlying code to make adding new elements to the game quite easy. With GameObjectManager and GameObject classes handling the work of drawing and updating the game elements and the Level in place to actually create the new elements, there is only a minimal amount of code required to implement new game elements. We will take advantage of this to add some enemy fighters to the game, and give the player some weapons to fight them with.

First, let’s take a look at the changes that have been made to the Level class.

package

{

import flash.events.*;

import flash.geom.*;

import flash.media.*;

import flash.net.*;

import flash.utils.*;

import mx.collections.ArrayCollection;

import mx.core.*;

public class Level

{

protected static var instance:Level = null;

protected static const TimeBetweenLevelElements:Number = 2;

protected static const TimeBetweenEnemies:Number = 3;

protected static const TimeBetweenClouds:Number = 2.5;

protected var timeToNextLevelElement:Number = 0;

protected var levelElementGraphics:ArrayCollection = new ArrayCollection();

protected var timeToNextEnemy:Number = 0;

protected var enemyElementGraphics:ArrayCollection = new ArrayCollection();

protected var timeToNextCloud:Number = 0;

static public function get Instance():Level

{

if ( instance == null )

instance = new Level();

return instance;

}

public function Level(caller:Function = null )

{

if ( Level.instance != null )

throw new Error( "Only one Singleton instance should be instantiated" );

levelElementGraphics.addItem( ResourceManager.SmallIslandGraphics);

levelElementGraphics.addItem( ResourceManager.BigIslandGraphics);

levelElementGraphics.addItem( ResourceManager.VolcanoIslandGraphics);

enemyElementGraphics.addItem( ResourceManager.SmallBluePlaneGraphics);

enemyElementGraphics.addItem( ResourceManager.SmallGreenPlaneGraphics);

enemyElementGraphics.addItem( ResourceManager.SmallWhitePlaneGraphics);

}

public function startup():void

{

timeToNextLevelElement = 0;

new Player().startupPlayer();

}

public function shutdown():void

{

}

public function enterFrame(dt:Number):void

{

// add a background element

timeToNextLevelElement -= dt;

if (timeToNextLevelElement <= 0)

{

timeToNextLevelElement = TimeBetweenLevelElements;

var graphics:GraphicsResource = levelElementGraphics.getItemAt( MathUtils.randomInteger(0, levelElementGraphics.length)) as GraphicsResource;

var backgroundLevelElement:BackgroundLevelElement = BackgroundLevelElement.pool.ItemFromPool as BackgroundLevelElement;

backgroundLevelElement.startupBackgroundLevelElement(

graphics,

new Point(Math.random() * Application.application.width, -graphics.bitmap.height),

ZOrders.BackgoundZOrder,

50);

}

// add an enemy

timeToNextEnemy -= dt;

if (timeToNextEnemy <= 0)

{

timeToNextEnemy = TimeBetweenEnemies;

var enemygraphics:GraphicsResource = enemyElementGraphics.getItemAt( MathUtils.randomInteger(0, enemyElementGraphics.length)) as GraphicsResource;

var enemy:Enemy = Enemy.pool.ItemFromPool as Enemy;

enemy.startupBasicEnemy(

enemygraphics,

new Point(Math.random() * Application.application.width, -enemygraphics.bitmap.height),

55);

}

// add cloud

timeToNextCloud -= dt;

if (timeToNextCloud <= dt)

{

timeToNextCloud = TimeBetweenClouds;

var cloudBackgroundLevelElement:BackgroundLevelElement = BackgroundLevelElement.pool.ItemFromPool as BackgroundLevelElement;

cloudBackgroundLevelElement. startupBackgroundLevelElement(

ResourceManager.CloudGraphics,

new Point(Math.random() * Application.application.width, -ResourceManager.CloudGraphics.bitmap.height),

ZOrders.CloudsBelowZOrder,

75);

}

}

}

}

The timeToNextEnemy / TimeBetweenEnemies and timeToNextCloud / TimeBetweenClouds pair of properties serve the same function as the timeToNextLevelElement / TimeBetweenLevelElements pair of properties (which was detailed in part 4) except they are used to add enemies and clouds respectively. The enemyElementGraphics property is used for the same purpose as the levelElementGraphics (which was also detailed in part 4) except here is it used to provide GraphicsResource’s when creating new enemies.

We have also added two new blocks of code in the enterFrame function to create the enemies and the clouds. This code is almost exactly the same as the block of code that is used to create the BackgroundLevelElement’s.

The clouds are implemented as a BackgroundLevelElement, except with a slightly faster scroll rate and a higher zOrder. This gives them the appearance of being at a higher altitude.

A new class, Enemy, has been created to represent the enemy fighters. Let’s look at that code now.