我是flash和as3编程的新手，这是我的第一个项目。我在这个项目上发现了错误
TypeError：错误＃1009：无法访问空对象引用的属性或方法。 在src.char :: Enemy / Remove（） 在src.screen :: Gameplay / Collision（） 在src.screen :: Gameplay / Routine（）
我认为错误的发生是因为游戏中没有函数Remove（），但我不确定是不是这样。这是敌人。
import flash.display.MovieClip;
import flash.events.Event;
import flash.events.TimerEvent;
import flash.utils.Timer;
public class Enemy extends MovieClip {
private var timer:Timer = new Timer(25);
public function Enemy(xPos:Number, yPos:Number) {
x = xPos;
y = yPos;
timer.addEventListener(TimerEvent.TIMER, MoveDown);
timer.start();
}
private function MoveDown(e:TimerEvent):void {
y += 3;
if (y>400) {
Remove();
}
}
public function Remove():void {
timer.stop();
timer.removeEventListener(TimerEvent.TIMER, MoveDown);
parent.removeChild(this);
}
}
这是gameplay.as
public class Gameplay extends MovieClip {
private var timer:Timer = new Timer(500);
private var player:Player;
public function Gameplay() {
addEventListener(Event.ADDED_TO_STAGE, InitKeyboard);
addEventListener(Event.ENTER_FRAME, Routine);
gameplayBack.addEventListener(MouseEvent.CLICK, GoToMap);
timer.addEventListener(TimerEvent.TIMER, OnTick);
timer.start();
InitPlayer();
InitLifePoint();
}
private function InitLifePoint():void {
lifePoint.gotoAndStop(1);
}
private function Routine(e:Event):void {
Collision();
}
private function Collision():void {
for (var i:int = 0; i < enemies.length; i++ ) {
if (player.hitTestObject(enemies[i])) {
PlayerHit();
enemies[i].Remove();
return;
}else {
for (var j:int = 0; j < bullets.length; j++ ) {
if (bullets[j].hitTestObject(enemies[i])) {
layerParticle.addChild(new Blast(bullets[j].x, bullets[j].y));
layerParticle.addChild(new Smoke(bullets[j].x, bullets[j].y));
bullets[j].Remove();
enemies[i].Remove();
scorePlay.text = int(scorePlay.text) + 10 + "";
trace(scorePlay.text);
return;
}
}
}
}
}
private var life:int = 1000;
private var currentLife:int = 1000;
private function PlayerHit():void {
currentLife -= 100;
if (currentLife <= 0) {
lifePoint.gotoAndStop(100);
GameOver();
}else {
lifePoint.gotoAndStop(100 - currentLife / life * 100);
}
}
private var result:Result = new Result();
private function GameOver():void {
result.youWin.alpha = 0;
result.ok.addEventListener(MouseEvent.CLICK, GoToMap);
result.x = 0;
result.y = 0;
addChild(result);
}
private function InitKeyboard(e:Event):void {
removeEventListener(Event.ADDED_TO_STAGE, InitKeyboard);
stage.addEventListener(KeyboardEvent.KEY_DOWN, KeyDown);
}
private function KeyDown(e:KeyboardEvent):void {
switch(e.keyCode) {
case Keyboard.LEFT: MoveLeft(); break;
case Keyboard.RIGHT: MoveRight(); break;
case Keyboard.SPACE: Fire(); break;
}
}
private var bullets:Array = new Array();
private function Fire():void {
var bullet:Bullet = new Bullet(player.x, player.y);
bullet.scaleX = 0.25;
bullet.scaleY = 0.25;
bullet.addEventListener(Event.REMOVED_FROM_STAGE, RemoveBulletArray);
layerParticle.addChild(bullet);
bullets.push(bullet);
}
private function RemoveBulletArray(e:Event):void {
removeEventListener(Event.REMOVED_FROM_STAGE, RemoveBulletArray);
var index:int = bullets.indexOf(Bullet(e.currentTarget), 0);
bullets.splice(index, 1);
}
private function MoveRight():void {
if (player.x < 550) {
player.x += 5;
}
}
private function MoveLeft():void {
if (player.x > 0) {
player.x -= 5;
}
}
private function InitPlayer():void {
player = new Player(550 * 0.5, 350);
layerChar.addChild(player);
}
private function OnTick(e:TimerEvent):void {
RandomEnemy();
}
private var enemies:Array = new Array();
private function RandomEnemy():void {
var enemy:Enemy = new Enemy(Math.random() * 550, 0);
enemy.addEventListener(Event.REMOVED_FROM_STAGE, RemoveFromArray);
layerChar.addChild(enemy);
enemies.push(enemy);
}
private var remaining:int = 10;
private function RemoveFromArray(e:Event):void {
removeEventListener(Event.REMOVED_FROM_STAGE, RemoveFromArray);
var index:int = enemies.indexOf(Enemy(e.currentTarget), 0);
enemies.slice(index, 1);
remaining--;
if (remaining == 0) GameWin();
}
private function GameWin():void {
result.youLose.alpha = 0;
result.score.text = scorePlay.text;
result.ok.addEventListener(MouseEvent.CLICK, GoToMap);
result.x = 0;
result.y = 0;
addChild(result);
}
private function GoToMap(e:MouseEvent):void {
dispatchEvent(new ScreenEvent(ScreenEvent.MAP));
}
}
答案 0 :(得分：1)
您的问题是Enemy.Remove（）方法中的NPE（空指针异常/错误）：
public function Remove():void {
timer.stop();
timer.removeEventListener(TimerEvent.TIMER, MoveDown);
parent.removeChild(this);
}
您的timer属性为空（我怀疑，查看您的代码）或parent属性。
在MovieClip parent属性中，如果添加了DisplayObject，则MovieClip会填充null，如果不是，则此属性为MovieClip。
您的问题可能是您要多次从if移除parent，或者尝试将其删除而不先添加它。
要确保这是问题，请首先添加if(parent != null)
{
parent.removeChild(this);
}
语句以检查MovieClip属性，如下所示：
{{1}}
注意：
这可能会解决您的NPE问题，但无法解决导致它的问题，这可能会导致您遇到越来越多的莫名其妙的错误。
仔细检查您的逻辑，确保删除之前添加的{{1}}，或者您不会删除多次。
答案 1 :(得分：0)
如果你这样观察，你会注意到碰撞功能中的缺陷：
for (var i:int = 0; i < enemies.length; i++) {
if (~) {
...
enemies[i].Remove();
...
} else {
for (~) {
if (~) {
...
enemies[i].Remove();
...
}
}
}
}
显然，在第二个 for 循环中，您可以轻松引用相同的敌人对象。
问题出现在您调用删除函数之后，因为通过执行parent.removeChild(this);您将对象的唯一引用移除到它的父对象。
您可以尝试执行以下操作之一：
enemies[i].Remove();代码移至最外圈。