我的AS3代码存在问题。错误是：
TypeError: Error #1009: Cannot access a property or method of a null object reference.
at mcEnemy/destroyEnemy()[/Users/deorka12/Documents/School/firstGame/mcEnemy.as:94]
at firstGame/checkEnemiesOffscreen()[/Users/deorka12/Documents/School/firstGame/firstGame.as:112]
at firstGame/gameLoop()[/Users/deorka12/Documents/School/firstGame/firstGame.as:63]
这就是我的代码：
package {
import flash.display.MovieClip;
import flash.events.KeyboardEvent;
import flash.ui.Keyboard;
import flash.events.Event;
import flash.utils.Timer;
import flash.events.TimerEvent;
// public function kan je ook gebruiken in een ander as. file
// private function kan je alleen gebruiken in hetzelfde as. file
public class firstGame extends MovieClip
{
public var mcPlayer:MovieClip;
private var leftKeyIsDown:Boolean;
private var rightKeyIsDown: Boolean;
private var aMissileArray: Array;
private var aEnemyArray: Array;
public function firstGame (){
//initilaiz variables
aMissileArray = new Array ();
aEnemyArray = new Array ();
//trace("First Game Loaded");
//Listern for key presses and relesead
stage.addEventListener(KeyboardEvent.KEY_UP, keyUp);
stage.addEventListener(KeyboardEvent.KEY_DOWN, keyDown);
//Setup game event loop
stage.addEventListener(Event.ENTER_FRAME, gameLoop);
// create a timer object
var tEnemyTimer : Timer = new Timer (1000);
// listener for timer intervals
tEnemyTimer.addEventListener(TimerEvent.TIMER, addEnemy);
// start out timer
tEnemyTimer.start();
}
private function addEnemy (e:TimerEvent) : void
{
//trace ("timer ticks")
// create a new enemy object
var newEnemy:mcEnemy = new mcEnemy ();
// add object to the stage
stage.addChild (newEnemy);
// add enemy to new enemy to a new enemy array
aEnemyArray.push(newEnemy);
trace (aEnemyArray.length);
}
private function gameLoop (e:Event) : void
{
playerControl();
clampPlayerToStage();
checkMissileOffscreen();
**checkEnemiesOffscreen();**
checkMissilesHitsEnemy();
}
private function checkMissilesHitsEnemy (): void
{
// loop trough current missiles
for (var i : int = 0 ; i < aMissileArray.length; i++)
{
// get our current missile in the i loop
var currentMissile : mcMissile = aMissileArray [i];
// loop trough all our enemies
// gebruik geen i want die is al gebruikt dus j
for (var j: int = 0 ; j < aEnemyArray.length; j++)
{
// get the current enemy in the j loop
var currentEnemy: mcEnemy = aEnemyArray [j];
// test if our current enemy is hitting our current missile
if(currentMissile.hitTestObject(currentEnemy))
{
// remove the missile
currentMissile.destroyMissile();
// remove the missile from missile array
aMissileArray.splice(i, 1);
// remove the enemy from the stage
**currentEnemy.destroyEnemy();**
// remove the enemy from the enemy array
aEnemyArray.splice(j, 1);
}
}
}
}
private function checkEnemiesOffscreen (): void
{
// loop trough all our enemies
for (var i:int = 0;i < aEnemyArray.length; i++)
{
// get our current ememy in the loop
var currentEnemy: mcEnemy = aEnemyArray [i];
// when enemy moves left and is has gone past the and of the left from the stage
if (currentEnemy.sDirection == "L" && currentEnemy.x - (currentEnemy.width/2))
{
// Remove enemy from our array
aEnemyArray.slice(i,1);
// Remove enemy from stage
currentEnemy.destroyEnemy();
} else
if (currentEnemy.sDirection == "R" && currentEnemy.x > stage.stageWidth + (currentEnemy.width/2))
{
// Remove enemy from our array
aEnemyArray.slice(i,1);
// Remove enemy from stage
currentEnemy.destroyEnemy();
}
}
}
private function checkMissileOffscreen():void
{
//Loop throw all our missiles in our missle array
// i = counter object
for (var i: int = 0; i < aMissileArray.length; i++)
{
//Get the current missile in the loop
var currentMissile : mcMissile = aMissileArray [i];
//Test if current missile is out the buttom of the screen
if (currentMissile.y > 450 )
{
//Remove current missile from the array
aMissileArray.splice(i,1);
//Destroy our missile
currentMissile.destroyMissile();
}
}
}
private function clampPlayerToStage ():void
{
// if our player is to the left of the stage
if (mcPlayer.x < (mcPlayer.width/2))
{
// set our player to left of the stage
mcPlayer.x = mcPlayer.width/2;
}
// if our player is to the right of the stage
else if (mcPlayer.x > (stage.stageWidth - (mcPlayer.width/2)))
{
//set our player to right of the stage
mcPlayer.x = stage.stageWidth - (mcPlayer.width/2);
}
}
private function playerControl ():void
{
// if our left key is down currently
if (leftKeyIsDown == true)
{
//move to left
mcPlayer.x -= 5;
}
// if our right key is currently down
if (rightKeyIsDown)
{
//move to right
mcPlayer.x += 5;
}
}
private function keyUp (e:KeyboardEvent): void
{
//trace(e.keyCode)
//if your left is released
if (e.keyCode == 37)
{
//left key is released
leftKeyIsDown = false;
}
//if your right is released
if (e.keyCode == 39)
{
//right key is released
rightKeyIsDown = false;
}
//if our spacebarr is released
if (e.keyCode == 32)
{
//fire a missile
fireMissile ();
}
}
private function fireMissile ():void
{
// create a new missisile object
var newMissile : mcMissile = new mcMissile ();
// add to stage
stage.addChild(newMissile);
// position missile
newMissile.x = mcPlayer.x;
newMissile.y = mcPlayer.y;
//add our new missile to our missile array
aMissileArray.push (newMissile);
trace(aMissileArray.length)
}
private function keyDown (e:KeyboardEvent): void
{
//trace(e.keyCode)
//if your left is pressed
if (e.keyCode == 37)
{
//left key is pressed
leftKeyIsDown = true;
}
//if your right is pressed
if (e.keyCode == 39)
{
//right key is pressed
rightKeyIsDown = true;
}
}
}
}
我的其他代码是：
package {
import flash.display.MovieClip;
import flash.events.Event;
public class mcEnemy extends MovieClip {
public var sDirection:String;
private var nSpeed:Number;
public function mcEnemy()
{
addEventListener(Event.ADDED_TO_STAGE, onAdd);
}
private function onAdd (e:Event): void
{
removeEventListener(Event.ADDED_TO_STAGE, onAdd);
init();
}
private function init ():void
{
// 3 frames
var nEnemies:Number = 3;
// pick random number between 1 and number of enemies
var nRandom:Number = randomNumber (1, nEnemies);
// Setup our playhead of this enemy clip to a random number
// Stop op frame 1,2 of 3
this.gotoAndStop(nRandom);
// Setup our enemys start position
setupStartPosition();
}
private function setupStartPosition (): void
{
// pick a random speed for the enemy
nSpeed = randomNumber (5,10);
// Pick random number for left or right, start position
var nLeftOrRight:Number = randomNumber (1,2);
// if our nLeftOrRight == 1 , enemy is on the left
if (nLeftOrRight == 1)
{
// start enemy on the left side
this.x = - (this.width/2);
sDirection = "R";
} else
{
// start enemy on the right side
this.x = stage.stageWidth + (this.width/2);
sDirection = "L";
}
// set a random hoogte for our enemy
// set a 2 varibele for min and max hoogte
var nMinAltitude: Number = stage.stageHeight/2;
var nMaxAltitude: Number = 400 - (this.height/2);
// Setup our enemies altitude to a random point between our min and max altitudes
this.y = randomNumber (nMinAltitude, nMaxAltitude);
// move our enemy
startMoving ();
}
private function startMoving (): void
{
addEventListener(Event.ENTER_FRAME, enemyLoop)
}
private function enemyLoop (e:Event ): void
{
// test in what direction our enemy is moving
// if our enemy is moving right
if (sDirection == "R")
{
// move our enemy right
this.x += nSpeed;
} else
{
this.x -= nSpeed;
}
}
// geeft random nummer tussen 0 en 1
function randomNumber (low:Number=0, high:Number=1) : Number
{
return Math.floor (Math.random() * (1+high-low)) + low;
}
public function destroyEnemy (): void
{
// remove enemys from the stage
**parent.removeChild(this);**
// remove any eventlisteners from enemy
removeEventListener(Event.ENTER_FRAME, enemyLoop);
}
}
}
我希望有人可以帮助我。抱歉我的英语不好。
答案 0 :(得分：0)
该错误表示属性parent为空，表示您的mcEnemy对象没有父对象。 mcEnemy对象尚未添加到显示列表中。
要解决此问题，您可以检查parent属性是否先设置：
if(parent)
{
parent.removeChild(this);
}