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我正在创建一个射击游戏。当我决定在到达舞台顶部时创建一种方法去除导弹后，我遇到了我的代码问题。我可以在没有任何问题的情况下运行该程序，但是我已经意识到，如果我拿着射击按钮，导弹不会从舞台上移开。但是，如果我点击拍摄按钮，导弹将从输出中打印出错误＃1009。Actionscript 3返回错误＃1009
有没有解决问题的方法？
这里是在错误发生后的导弹飞到启用了调试阶段的顶部：
TypeError: Error #1009: Cannot access a property or method of a null object reference.
at Missle/destroyMissle()[E:\Experiment\ExperimentProject\Missle.as:39]
at main/checkMissleOffScreen()[E:\Experiment\ExperimentProject\main.as:63]
at main/eventUpdated()[E:\Experiment\ExperimentProject\main.as:51]
下面是主要的类：
package
{
import flash.display.MovieClip;
import flash.events.Event;
import flash.events.KeyboardEvent;
/**
* ...
* @author test
*/
public class main extends MovieClip
{
//Objects
public var rect:MovieClip;
public var missle:Missle;
//Array
private var missleArray:Array;
//Keyboard section
var leftKeyIsDown:Boolean;
var rightKeyIsDown:Boolean;
var upKeyIsDown:Boolean;
var downKeyIsDown:Boolean;
var spaceKeyIsDown:Boolean;
//Speed
var characterSpeed:Number = 15;
//Main constructor
public function main()
{
//Array initializer
missleArray = new Array();
missle = new Missle();
//Update events listeners.
stage.addEventListener(Event.ENTER_FRAME, eventUpdated);
//Update keyboard events listeners
stage.addEventListener(KeyboardEvent.KEY_DOWN, keyPressed);
stage.addEventListener(KeyboardEvent.KEY_UP, keyUnpressed);
}
//Events functions
//This functions updated everytime the object is move
private function eventUpdated(e:Event):void
{
playerMoving();
playerClampMoving();
checkMissleOffScreen();
}
private function checkMissleOffScreen():void
{
for (var i = 0; i < missleArray.length; i++)
{
var currentMissle:Missle = missleArray[i];
if (currentMissle.y < 0)
{
missleArray.splice(i, 1);
missle.destroyMissle();
}
}
}
private function playerClampMoving():void
{
if (rect.x < 0)
{
rect.x = 0;
}
if (rect.x > stage.stageWidth - rect.width)
{
rect.x = stage.stageWidth - rect.width;
}
if (rect.y < 0)
{
rect.y = 0;
}
if (rect.y > stage.stageHeight - rect.height)
{
rect.y = stage.stageHeight - rect.height;
}
}
private function playerMoving():void
{
if (leftKeyIsDown == true)
{
rect.x -= characterSpeed;
}
if (rightKeyIsDown == true)
{
rect.x += characterSpeed;
}
if (upKeyIsDown == true)
{
rect.y -= characterSpeed;
}
if (downKeyIsDown == true)
{
rect.y += characterSpeed;
}
if (spaceKeyIsDown == true)
{
shootingMissle();
}
}
private function shootingMissle():void
{
missle = new Missle();
missle.x = rect.x + (rect.width/2);
missle.y = rect.y;
missleArray.push(missle);
trace(missleArray.length);
stage.addChild(missle);
}
//Keyboard functions
//Check to see whether the user releases the keyboard
private function keyUnpressed(e:KeyboardEvent):void
{
if (e.keyCode == 37)
{
leftKeyIsDown = false;
}
if (e.keyCode == 39)
{
rightKeyIsDown = false;
}
if (e.keyCode == 40)
{
downKeyIsDown = false;
}
if (e.keyCode == 38)
{
upKeyIsDown = false;
}
if (e.keyCode == 32)
{
spaceKeyIsDown = false;
}
}
//Check to see whether the user presses the keyboard
private function keyPressed(e:KeyboardEvent):void
{
if (e.keyCode == 37)
{
leftKeyIsDown = true;
}
if (e.keyCode == 39)
{
rightKeyIsDown = true;
}
if (e.keyCode == 40)
{
downKeyIsDown = true;
}
if (e.keyCode == 38)
{
upKeyIsDown = true;
}
if (e.keyCode == 32)
{
spaceKeyIsDown = true;
}
}
}
}
这里的导弹武器的类别：
package
{
import flash.display.Sprite;
import flash.events.Event;
/**
* ...
* @author test
*/
public class Missle extends Sprite
{
public function Missle()
{
addEventListener(Event.ADDED_TO_STAGE, onAdd);
}
private function onAdd(e:Event):void
{
removeEventListener(Event.ADDED_TO_STAGE, onAdd);
//Objects are on the stage
init();
}
private function init():void
{
addEventListener(Event.ENTER_FRAME, missleLaunch);
}
private function missleLaunch(e:Event):void
{
this.y -= 15;
}
public function destroyMissle():void
{
parent.removeChild(this);
removeEventListener(Event.ENTER_FRAME, missleLaunch);
}
}
}