Problemo

Question

I'm having a weird problem and am wondering if someone can help me fix it. I'm trying to make a game with a player spaceship that is controlled by keyboard input. But it won't move with the keyboard input until I click the mouse button. the problem might be with the game framework that I'm using from a download for the book, "the Essential Guide to Flash Games," but it might just be something I'm doing wrong in the code. I have the variables _vx and _vy set to zero initially then they are suppose to change when I press the arrow keys, in order for the ship to move. Here's the class with the keyboard input in it....
package 
// Import necessary classes from the flash libraries
import flash.display.Sprite;
import flash.events.*;
import flash.events.MouseEvent;
import flash.events.KeyboardEvent;
import flash.display.Bitmap;
import flash.display.BitmapData;
import flash.geom.Point;
import flash.ui.Mouse;
import flash.ui.Keyboard;
import com.efg.framework.CustomEventSound;
import com.efg.framework.Game;
import com.efg.framework.CustomEventLevelScreenUpdate;
import com.efg.framework.CustomEventScoreBoardUpdate;
public class Lunar_Mayhem extends Game
private var gameWidth:int;
private var gameHeight:int;
private const SPEED:Number = .4;
//New Game
private var score:int;
private var level:int;
private var ships:int;
private var shots:int;
private var isGameOver:Boolean = false;
//New Level
private var explodeArray:Array;
private var shotArray:Array;
private var shipArray:Array;
private var crosshairs:Bitmap;
public var _vx:Number = 0;
public var _vy:Number = 0;
private var tempShot:Shot;
private var _player:Ship;
//private var testLevel:TestLevel;
private var tempShip:Ship;
//private var tempExplode:Explosion;
public function Lunar_Mayhem() {
init();
//testLevel =  new TestLevel(_vx,_vy);
//this.addChild(testLevel);
//tempShot = new Shot((testLevel._player.x +testLevel._player.width/2-5),(testLevel._player.y + testLevel._player.height/2),0,0);
public function init(){
override public function newGame():void {
level = 0 ;
score = 0;
ships = 3;
shots = 0;
isGameOver = false;
stage.addEventListener(KeyboardEvent.KEY_DOWN,onKeyDown);
stage.addEventListener(KeyboardEvent.KEY_UP, onKeyUp);
public function onKeyDown(e:KeyboardEvent):void
switch (e.keyCode)
  case Keyboard.LEFT:
    _vx -= SPEED *.5;
    break;
  case Keyboard.RIGHT:
  _vx += SPEED * .5;
    break;
  case Keyboard.UP:
  _vy -= SPEED;
    break;
  case Keyboard.DOWN:
    break;
public function onKeyUp(e:KeyboardEvent):void
  if (e.keyCode == Keyboard.LEFT
  || e.keyCode == Keyboard.RIGHT)
     //_vx = 0;
  if (e.keyCode == Keyboard.UP
  || e.keyCode == Keyboard.DOWN)
     //_vy = 0;
override public function newLevel():void {
_player = new Ship();
this.addChild(_player);
explodeArray = [];
shotArray = [];
shipArray = [];
level++;
dispatchEvent(new CustomEventLevelScreenUpdate(CustomEventLevelScreenUpdate.UPDATE_TEXT, String(level)));
dispatchEvent(new CustomEventScoreBoardUpdate(CustomEventScoreBoardUpdate.UPDATE_TEXT,Main.SCORE_BOARD_SHOT S,String(shots)));
dispatchEvent(new CustomEventScoreBoardUpdate(CustomEventScoreBoardUpdate.UPDATE_TEXT,Main.SCORE_BOARD_SHIP S,String(ships)));
override public function runGame():void {
update(_vx,_vy);
render();
checkCollisions();
checkforEndLevel();
checkforEndGame();
trace(_vy);
trace(_vx);
I've only included this much of the code because I think this is where the problem is. The override public function runGame is the game loop. update and render call the ship class which looks like this:
package 
// Import necessary classes from the flash libraries
import flash.display.Shape;
import flash.display.Sprite;
import flash.events.*;
import flash.display.Bitmap;
import flash.display.BitmapData;
import flash.geom.Point;
public class Ship extends Sprite
private const SPEED:Number = .4;
private var gameWidth:int;
private var gameHeight:int;
public var imageBitmapData:BitmapData;
public var image:Bitmap;
public var nextLocation:Point;
public var playerHalfWidth:Number;
public var playerHalfHeight:Number;
//scroll with player variables
public var gravity:Number;
private var _energy:Number = 100;
private var hitVal:Number = 0;
public function Ship() {
init();
public function init():void {
//***** Flex *****
//imageBitmapData = new ShipGif().bitmapData;
//**** Flash *****
nextLocation = new Point(0,0);
imageBitmapData = new ShipGif(63, 53);
image = new Bitmap(imageBitmapData);
addChild(image);
gameWidth = 550;
gameHeight = 400;
gravity = .55;
playerHalfWidth = 63 / 2;
playerHalfHeight = 53 / 2;
public function update(_vx:Number,_vy:Number):void {
nextLocation.x += _vx;
nextLocation.y += _vy;
nextLocation.y += gravity;
public function render():void {
x = nextLocation.x;
y = nextLocation.y;
//Dispose is needed to get rid oo unwanted objects and get them ready for garbage collection
public function dispose():void {
removeChild(image);
imageBitmapData.dispose();
image = null;
If anyone could take a quick look and see what's wrong that would be great. Thanks

Answer 1

use the trace() function to debug your code.  it's usually easiest to work backwards checking the lines of code that, you think, should cause your ship to move.  continue working backwards until you find the proximate cause of the problem.