在actionscript-3中加载图像而不是使用绘制对象时遇到问题

我试着从一部佳能上射出一个球，这很好，但我想把一部佳能从一部画好的佳能变成一部佳能的图像。 但是当我这样做的时候，当我点击舞台射出球时，我会得到以下错误，而使用绘制的版本，球会按计划射出：

TypeError:错误#1009:无法访问空对象引用的属性或方法。 代码2/createNewBullet（）处 代码为2/mouseClickHandler（）

这是有效的代码：

private function init():void {

        drawBoard = new MovieClip;
        drawBoard.graphics.beginFill(0xFFFFFF, 0); // white transparant
        drawBoard.graphics.drawRect(0, 0, gameWidth, gameHeight);
        drawBoard.graphics.endFill();
        addChild(drawBoard);
        // create canon
        canon = new MovieClip;
        canon = new MovieClip;
        canon.graphics.beginFill(0x000000);
        canon.graphics.drawRect(0, -10, 50, 20);
        canon.graphics.endFill();
        canon.rotation = -45;
        canon.x = 25;
        canon.y = gameHeight;
        addChild(canon);

package {

// Copyright 2010-2011 - Seinia.com
// Find more crazy good AS3.0 tutorials and games on Seinia.com!

// imports
// --------------------------------------------------------------------------------------
import flash.display.MovieClip;
import flash.events.Event;
import flash.events.MouseEvent;
import flash.geom.Point;
import flash.events.*;
import flash.net.URLRequest;
import flash.display.Loader;
import flash.display.Sprite;

// Game class (MovieClip extension)
// --------------------------------------------------------------------------------------
public class code2 extends MovieClip {

    // game properties
    // --------------------------------------------------------------------------------------
    var drawBoard:MovieClip;
    var background:MovieClip;
    var gameWidth:int = 600;
    var gameHeight:int = 300;
    var gravity:Number = .4;
    var bullets:Array;
    var canon:MovieClip;

    // constructor
    // --------------------------------------------------------------------------------------
    public function code2():void {
        this.focusRect = false;
        this.init();
        addEventListener(Event.ENTER_FRAME, enterFrameHandler, false, 0, true);
        addEventListener(MouseEvent.CLICK, mouseClickHandler, false, 0, true);
        bullets = new Array();
    }

    // init the game
    // --------------------------------------------------------------------------------------
    private function init():void {
        // create drawboard (the important movieclip, that holds all visible elements)
        drawBoard = new MovieClip;
        drawBoard.graphics.beginFill(0xFFFFFF, 0); // white transparant
        drawBoard.graphics.drawRect(0, 0, gameWidth, gameHeight);
        drawBoard.graphics.endFill();
        addChild(drawBoard);

        var canon:Loader = new Loader();
        var fileRequest:URLRequest = new URLRequest("cannon1.png");
        canon.load(fileRequest);
        canon.rotation = -45;
        canon.x = 25;
        canon.y = gameHeight;
        addChild(canon);


    }

    // mouse click handler
    // --------------------------------------------------------------------------------------
    private function mouseClickHandler(event:MouseEvent):void {
        createNewBullet();
    }

    // function to create a new bullet
    // --------------------------------------------------------------------------------------
    private function createNewBullet():void {
        // init and draw bullet
        var bullet:MovieClip = new MovieClip;
        bullet.graphics.beginFill(0xff0000);
        bullet.graphics.drawCircle(0, 0, 10);
        bullet.graphics.endFill();
        // define bullet start point and speed
        var cos:Number = Math.cos(canon.rotation * Math.PI / 180);
        var sin:Number = Math.sin(canon.rotation * Math.PI / 180);
        var speed:Number = 8;
        bullet.x = canon.x + cos * canon.width;
        bullet.y = canon.y + sin * canon.width;
        bullet.vx = cos * speed;
        bullet.vy = sin * speed;
        bullets.push(bullet);
        addChild(bullet);
    }

    // enter frame handler
    // --------------------------------------------------------------------------------------
    private function enterFrameHandler(event:Event):void {
        for (var i = 0; i < bullets.length; i++ ) {
            // gravity
            bullets[i].vy += gravity;
            // move bullet
            bullets[i].x += bullets[i].vx;
            bullets[i].y += bullets[i].vy;
            // remove star from stage?
            if (bullets[i].y >= gameHeight) {
                removeChild(bullets[i]);
                bullets.splice(i, 1);
            }
        }
    }
}

这就是我试图为大炮使用图像而不是绘制的矩形所做的 （（图像加载良好，但会导致错误））

如果需要，这是完整的代码：

private function init():void {

        drawBoard = new MovieClip;
        drawBoard.graphics.beginFill(0xFFFFFF, 0); // white transparant
        drawBoard.graphics.drawRect(0, 0, gameWidth, gameHeight);
        drawBoard.graphics.endFill();
        addChild(drawBoard);
        // create canon
        canon = new MovieClip;
        canon = new MovieClip;
        canon.graphics.beginFill(0x000000);
        canon.graphics.drawRect(0, -10, 50, 20);
        canon.graphics.endFill();
        canon.rotation = -45;
        canon.x = 25;
        canon.y = gameHeight;
        addChild(canon);

package {

// Copyright 2010-2011 - Seinia.com
// Find more crazy good AS3.0 tutorials and games on Seinia.com!

// imports
// --------------------------------------------------------------------------------------
import flash.display.MovieClip;
import flash.events.Event;
import flash.events.MouseEvent;
import flash.geom.Point;
import flash.events.*;
import flash.net.URLRequest;
import flash.display.Loader;
import flash.display.Sprite;

// Game class (MovieClip extension)
// --------------------------------------------------------------------------------------
public class code2 extends MovieClip {

    // game properties
    // --------------------------------------------------------------------------------------
    var drawBoard:MovieClip;
    var background:MovieClip;
    var gameWidth:int = 600;
    var gameHeight:int = 300;
    var gravity:Number = .4;
    var bullets:Array;
    var canon:MovieClip;

    // constructor
    // --------------------------------------------------------------------------------------
    public function code2():void {
        this.focusRect = false;
        this.init();
        addEventListener(Event.ENTER_FRAME, enterFrameHandler, false, 0, true);
        addEventListener(MouseEvent.CLICK, mouseClickHandler, false, 0, true);
        bullets = new Array();
    }

    // init the game
    // --------------------------------------------------------------------------------------
    private function init():void {
        // create drawboard (the important movieclip, that holds all visible elements)
        drawBoard = new MovieClip;
        drawBoard.graphics.beginFill(0xFFFFFF, 0); // white transparant
        drawBoard.graphics.drawRect(0, 0, gameWidth, gameHeight);
        drawBoard.graphics.endFill();
        addChild(drawBoard);

        var canon:Loader = new Loader();
        var fileRequest:URLRequest = new URLRequest("cannon1.png");
        canon.load(fileRequest);
        canon.rotation = -45;
        canon.x = 25;
        canon.y = gameHeight;
        addChild(canon);


    }

    // mouse click handler
    // --------------------------------------------------------------------------------------
    private function mouseClickHandler(event:MouseEvent):void {
        createNewBullet();
    }

    // function to create a new bullet
    // --------------------------------------------------------------------------------------
    private function createNewBullet():void {
        // init and draw bullet
        var bullet:MovieClip = new MovieClip;
        bullet.graphics.beginFill(0xff0000);
        bullet.graphics.drawCircle(0, 0, 10);
        bullet.graphics.endFill();
        // define bullet start point and speed
        var cos:Number = Math.cos(canon.rotation * Math.PI / 180);
        var sin:Number = Math.sin(canon.rotation * Math.PI / 180);
        var speed:Number = 8;
        bullet.x = canon.x + cos * canon.width;
        bullet.y = canon.y + sin * canon.width;
        bullet.vx = cos * speed;
        bullet.vy = sin * speed;
        bullets.push(bullet);
        addChild(bullet);
    }

    // enter frame handler
    // --------------------------------------------------------------------------------------
    private function enterFrameHandler(event:Event):void {
        for (var i = 0; i < bullets.length; i++ ) {
            // gravity
            bullets[i].vy += gravity;
            // move bullet
            bullets[i].x += bullets[i].vx;
            bullets[i].y += bullets[i].vy;
            // remove star from stage?
            if (bullets[i].y >= gameHeight) {
                removeChild(bullets[i]);
                bullets.splice(i, 1);
            }
        }
    }
}

包{
//版权所有2010-2011-Seinia.com
//在Seinia.com上找到更多疯狂好的AS3.0教程和游戏！
//进口
// --------------------------------------------------------------------------------------
导入flash.display.MovieClip；
导入flash.events.Event；
导入flash.events.MouseEvent；
导入flash.geom.Point；
导入flash.events.*；
导入flash.net.URLRequest；
导入flash.display.Loader；
导入flash.display.Sprite；
//游戏类（MovieClip扩展）
// --------------------------------------------------------------------------------------
公共类代码2扩展了MovieClip{
//游戏属性
// --------------------------------------------------------------------------------------
var抽油板：MovieClip；
背景：MovieClip；
变量gameWidth:int=600；
变量gameHeight:int=300；
变量重力：数字=0.4；
变量：数组；
var佳能：电影唇；
//建造师
// --------------------------------------------------------------------------------------
公共函数代码2（）：void{
this.focusRect=false；
this.init（）；
addEventListener（Event.ENTER_FRAME，enterFrameHandler，false，0，true）；
addEventListener（MouseEvent.CLICK、mouseClickHandler、false、0、true）；
项目符号=新数组（）；
}
//开始游戏
// --------------------------------------------------------------------------------------
私有函数init（）：void{
//创建drawboard（包含所有可见元素的重要movieclip）
drawBoard=新的MovieClip；
drawBoard.graphics.beginll（0xFFFFFF，0）；//白色透明
drawBoard.graphics.drawRect（0，0，游戏宽度，游戏高度）；
drawBoard.graphics.endFill（）；
addChild（绞车）；
变量佳能：加载器=新加载器（）；
var fileRequest:URLRequest=newurlrequest（“cannon1.png”）；
佳能加载（文件请求）；
佳能旋转=-45；
佳能x=25；
佳能y=游戏高度；
addChild（佳能）；
}
//鼠标点击处理程序
// --------------------------------------------------------------------------------------
专用函数mouseClickHandler（事件：MouseEvent）：无效{
createNewBullet（）；
}
//函数创建新的项目符号
// --------------------------------------------------------------------------------------
私有函数createNewBullet（）：void{
//初始化并提取子弹
var bullet:MovieClip=新的MovieClip；
bullet.graphics.beginll（0xff0000）；
项目符号。图形。画圈（0，0，10）；
bullet.graphics.endFill（）；
//定义项目符号起点和速度
变量cos:Number=Math.cos（canon.rotation*Math.PI/180）；
变量sin:Number=Math.sin（canon.rotation*Math.PI/180）；
var速度：数字=8；
bullet.x=佳能.x+cos*佳能宽度；
bullet.y=canon.y+sin*canon.width；
bullet.vx=cos*速度；
bullet.vy=sin*速度；
子弹。推（子弹）；
addChild（子弹）；
}
//输入框架处理程序
// --------------------------------------------------------------------------------------
私有函数enterFrameHandler（事件：事件）：void{
对于（变量i=0；i=游戏高度）{
removeChild（子弹[i]）；
项目符号.拼接（i，1）；
}
}
}
}

---

}

canon

在您的

createNewBullet（）

方法中没有作用域

您需要将

canon

声明为类成员变量

目前，canon是

init（）

方法的局部变量

正如评论员所指出的，您确实需要在声明中将佳能更改为加载器类型。

问题在于

var canon:MovieClip;

定义为私有变量，在所有类方法中都可用，其中

var canon:Loader = new Loader();

您在init中定义的函数仅在此函数范围内可用。函数结束后，将丢弃函数范围中定义的所有变量。 还要注意，第一个和第二个变量是两个不同的变量

要解决您的问题，您应该将类变量设置为加载器 在初始化函数期间，创建加载程序并为其赋值。这样，它将在这个类中的所有函数中都可用，例如

package {

// Copyright 2010-2011 - Seinia.com
// Find more crazy good AS3.0 tutorials and games on Seinia.com!

// imports
// --------------------------------------------------------------------------------------
import flash.display.MovieClip;
import flash.events.Event;
import flash.events.MouseEvent;
import flash.geom.Point;
import flash.events.*;
import flash.net.URLRequest;
import flash.display.Loader;
import flash.display.Sprite;

// Game class (MovieClip extension)
// ------------------------------------------------------------------------------------    --
public class code2 extends MovieClip {

    // game properties
    // --------------------------------------------------------------------------------    ------
    var drawBoard:MovieClip;
        var background:MovieClip;
    var gameWidth:int = 600;
    var gameHeight:int = 300;
    var gravity:Number = .4;
    var bullets:Array;
    var canon:Loader;

    // constructor
    // --------------------------------------------------------------------------------    ------
    public function code2():void {
        this.focusRect = false;
        this.init();
        addEventListener(Event.ENTER_FRAME, enterFrameHandler, false, 0, true);
        addEventListener(MouseEvent.CLICK, mouseClickHandler, false, 0, true);
        bullets = new Array();
    }

    // init the game
    // --------------------------------------------------------------------------------    ------
    private function init():void {
        // create drawboard (the important movieclip, that holds all visible elements)
        drawBoard = new MovieClip;
        drawBoard.graphics.beginFill(0xFFFFFF, 0); // white transparant
        drawBoard.graphics.drawRect(0, 0, gameWidth, gameHeight);
        drawBoard.graphics.endFill();
        addChild(drawBoard);

        canon = new Loader();
        var fileRequest:URLRequest = new URLRequest("cannon1.png");
        canon.load(fileRequest);
        canon.rotation = -45;
        canon.x = 25;
        canon.y = gameHeight;
        addChild(canon);


    }

    // mouse click handler
    // --------------------------------------------------------------------------------    ------
    private function mouseClickHandler(event:MouseEvent):void {
        createNewBullet();
    }

    // function to create a new bullet
    // --------------------------------------------------------------------------------    ------
    private function createNewBullet():void {
        // init and draw bullet
        var bullet:MovieClip = new MovieClip;
        bullet.graphics.beginFill(0xff0000);
        bullet.graphics.drawCircle(0, 0, 10);
        bullet.graphics.endFill();
        // define bullet start point and speed
        var cos:Number = Math.cos(canon.rotation * Math.PI / 180);
        var sin:Number = Math.sin(canon.rotation * Math.PI / 180);
        var speed:Number = 8;
        bullet.x = canon.x + cos * canon.width;
        bullet.y = canon.y + sin * canon.width;
        bullet.vx = cos * speed;
        bullet.vy = sin * speed;
        bullets.push(bullet);
        addChild(bullet);
    }

    // enter frame handler
    // --------------------------------------------------------------------------------    ------
    private function enterFrameHandler(event:Event):void {
        for (var i = 0; i < bullets.length; i++ ) {
            // gravity
                bullets[i].vy += gravity;
            // move bullet
            bullets[i].x += bullets[i].vx;
            bullets[i].y += bullets[i].vy;
            // remove star from stage?
            if (bullets[i].y >= gameHeight) {
                removeChild(bullets[i]);
                bullets.splice(i, 1);
            }
        }
    }
}

包{
//版权所有2010-2011-Seinia.com
//在Seinia.com上找到更多疯狂好的AS3.0教程和游戏！
//进口
// --------------------------------------------------------------------------------------
导入flash.display.MovieClip；
导入flash.events.Event；
导入flash.events.MouseEvent；
导入flash.geom.Point；
导入flash.events.*；
导入flash.net.URLRequest；
导入flash.display.Loader；
导入flash.display.Sprite；
//游戏类（MovieClip扩展）
// ------------------------------------------------------------------------------------    -