AS3：TypeError：エラー＃1009：nullオブジェクト参照のプロパティまたはメソッドにアクセスできません

Question

私は割り当てのためのフラッシュゲームに取り組んできましたが、これまでのところ本当の頭痛でした。 （アイテム、プレイヤーと敵のリセット、スコアは変わらない）レベルアップするためにスクリーン上のすべてのアイテムを集める、5回ヒットするとあなたは得る画面上のゲーム。

私は面倒な奇妙なエラーが発生しました。なしのアイテムとゲームオーバーを取得するすべてのエラーを与え、ゲームの罰金を（一見）リセットしますが、問題はありません。

*エラーで結果を介してゲームを取得するときに任意の項目を持つ1009

*クリックをすべてのアイテムを収集すると、「lvlUp」機能が提供されますが、何も起こらず、ifステートメントはトリガーしません。

私はこの問題で1日を過ごしましたが、数回全部を壊してしまったので、ここで経験豊富なコーダーと相談しました。

package 
{ 

import flash.events.Event; 
import flash.events.MouseEvent; 
import flash.display.MovieClip; 
import flash.geom.Rectangle; 
import player; 

public class Memento extends MovieClip 
{ 
    //importing required variables 
    private var onScreenContent:Array; 
    private var playerSkill:int; 
    private var myXY:Array; 
    private var mySpeed:int; 
    private var border:Rectangle; 
    private var myMaxItems:int; 
    private var numItems:int; 
    private var numEnemies:int; 
    private var maxEnemies:int; 
    private var characterMC:player; 
    public var sanity:int; 
    public var mementos:int; 
    public var currentMementos:int; 

    //CONSTRUCTOR 
    public function Memento() 
    { 
     trace("initialising DOS game"); 
     //simulates a selected skill level 
     playerSkill = 3; 
     sanity = 5; 
     mementos = 0; 
     onScreenContent = new Array ; 
     border = new Rectangle(30,180,870,750); 
    } 

    //code to add character into game at correct position 
    private function addCharacter():void 
    { 
     trace("Adding the character"); 
     //set the initial values to character starting pos 
     var myXY:Array = [480,900]; 
     var mySpeed:int = playerSkill + 6; 
     //create and add a new player to screen 
     characterMC = new player(myXY,border,mySpeed); 
     addChild(characterMC); 
     characterMC.focusRect = false; 
     stage.focus = characterMC; 
    }//end function addCharacter 
    //code to add items into game 
    private function addItems():void 
    { 
     trace("Initialising items"); 
     //amount of items 
     var myMaxItems:int = playerSkill + 1; 
     //adding the items one at a time 
     for (var numItem:int = 0; numItem < myMaxItems; numItem++) 
     { 
      var thisItem:collect = new collect(border,playerSkill,characterMC); 
      thisItem.name = "Item"; 
      //adding item to stage 
      onScreenContent.push(thisItem); 
      addChild(thisItem); 
     }//end for statement 
    }//end function addItems 
    //code to add enemies into game 
    private function addEnemy():void 
    { 
     trace("Adding Enemies"); 
     //setting initial number of enemies to match game/skill level 
     var maxEnemies:int = playerSkill + 1; 
     //adding enemies one by one using a loop 
     for (var numEnemies:int = 0; numEnemies < maxEnemies; numEnemies++) 
     { 
      //creating a new enemy 
      var thisEnemy:enemy = new enemy(border,playerSkill,characterMC); 
      thisEnemy.name = "Enemy"; 
      trace("adding enemies to stage"); 
      onScreenContent.push(thisEnemy); 
      addChild(thisEnemy); 
     } 
    }//end function addEnemy 
    //code to update game scores 
    public function updateScores(myMC: MovieClip):void 
    { 
     //change player score if they collide with enemy or item 
     mementos += myMC.scoreMod; 
     sanity += myMC.healthMod; 
     if (currentMementos == 4) 
     { 
      trace("lvlup"); 
      levelUp(); 
      currentMementos = 0; 
     }//end if statement 
     if (myMC.name.indexOf("item") != -1) 
     { 
      var myIndex:int = onScreenContent.indexOf(myMC); 
      onScreenContent.splice(myIndex, 1); 
      currentMementos++; 
     }//end if statement 
     trace("updating player score"); 
     //run updatescores function 
     displayScores(); 
     //run gameover check 
     if (sanity <= 0) 
     { 
      trace("game over prompted"); 
      gameOver(); 
     }//end if statement 
    } 
    //function to update scores 
    private function displayScores():void 
    { 
     //update dynamic text fields 
     lifeDisplay.text = "*" + sanity; 
     scoreDisplay.text = "Mementos: " + mementos; 
     trace("displaying updated scores"); 
    } 
    //function to level up 
    private function levelUp():void 
    { 
     // resetting all items 
     clearObjects(); 
     removeChild(characterMC); 
     playerSkill += 1; 
     //resetting game stage 
     addCharacter(); 
     addItems(); 
     addEnemy(); 
    } 

    public function clearObjects():void 
    { 
     //removing all remaining game objects 
     for each (var myObj in onScreenContent) 
     { 
      myObj.removeAsset(); 
      myObj = null; 
     } 

     // reset the array for next level 
     onScreenContent = new Array(); 
    } 

    //function to return from map stage back to main menu 
    function exitMap(event:MouseEvent):void 
    { 
     gotoAndStop(1); 
     //removing player 
     removeChild(characterMC); 
     clearObjects(); 
     mementos = 0; 
     sanity = 5; 
     currentMementos = 0; 
    }//end function exitMap 
    //function to execute game over 
    private function gameOver():void 
    { 
     //game over script 
     trace("game over"); 
     gotoAndStop(4); 
     clearObjects(); 
     removeChild(characterMC); 
     mementos = 0; 
     sanity = 5; 
     currentMementos = 0; 
    } 
}//end class 
}//end package 

敵のクラスコード：

package 
{ 

import flash.events.Event; 
import flash.events.MouseEvent; 
import flash.display.MovieClip; 
import flash.geom.Rectangle; 

public class enemy extends MovieClip 
{ 

    private var borderEnemy:Rectangle; 
    private var charNum:int; 
    private var charSpeed:int; 
    private var charDir:int; 
    private var offset:int; 
    private var characterMC:MovieClip; 
    public var healthMod:int; 
    public var scoreMod:int; 

    //CONSTRUCTOR FUNCTION 
    public function enemy(myBorder:Rectangle, mySkill:int, player:MovieClip) 
    { 
     //set values 
     trace("initialising an Enemy"); 
     mySkill = 3; 
     characterMC = player; 
     borderEnemy = new Rectangle(50,180,840,750); 
     //setting constraing area 
     borderEnemy = myBorder; 
     offset = 20; 
     //values of lives/scores 
     healthMod = -1; 
     scoreMod = 0; 
     //nasty type linked to mySkill 
     charNum = Math.ceil(Math.random() * (mySkill + 2)); 
     charSpeed = charNum + 1; 
     //what can I hit? 
     //eventlistener: starts code when character enters stage 
     addEventListener(Event.ADDED_TO_STAGE, initEnemy); 
     addEventListener(Event.ENTER_FRAME, checkCollision); 
    }//end function enemy 

    //function to initiate enemy 
    private function initEnemy(evt:Event):void 
    { 
     //displaying the enemy frame (appearence) according to charNum 
     gotoAndStop(charNum); 
     //setting item positon, linked to function 
     setPosition(); 
     //start movement of enemy, linked to function 
     addEventListener(Event.ENTER_FRAME, moveEnemy); 
     //remove unneeded listener after initiation 
     removeEventListener(Event.ADDED_TO_STAGE,initEnemy); 
    }//end function initEnemy 

    //function to set enemy position 
    private function setPosition():void 
    { 
     //setting enemy positions 
     //trace("setting enemy position"); 
     //code to determine enemy direction 
     charDir = Math.floor(Math.random() * 2); 
     //trace("charDir value is " + charDir); 
     //code to determine enemy location (vertically) 
     var myRand:int = Math.ceil(Math.random() * 8) * (Math.ceil(Math.random() * 5) + 2); 
     if (charDir < 1) 
     { 
      //trace("char entering from left"); 
      //random option 1: character appears from the left 
      charDir = 1; 
      this.x = borderEnemy.left - offset - myRand; 
      this.scaleX = 1; 
     } 
     else 
     { 
      //trace("char entering from right"); 
      //random option 2: character appears from the right 
      charDir = -1; 
      this.x = borderEnemy.right + offset + myRand; 
      this.scaleX = -1; 
     } 
     //set verticle position using myRand 
     var myHeight:int = borderEnemy.bottom - borderEnemy.top - offset * 1; 
     this.y = Math.ceil(Math.random() * myHeight) + borderEnemy.top * 1; 
    }//end function setPosition 

    //function to move enemies 
    private function moveEnemy(evt:Event):void 
    { 
     if (charDir < 1) 
     { 
      this.x += - charSpeed - 10; 
     } 
     else 
     { 
      this.x += charSpeed + 10; 
     } 
     //reset character as it hits the border 
     if (this.x < borderEnemy.left - 40 || this.x > borderEnemy.right + 40) 
     { 
      setPosition(); 
     } 
    }//end function moveEnemy 

    //function to check for collisions between player and enemies 
    private function checkCollision(evt:Event):void 
    { 
     //detecting if enemy has hit the player character 
     if (this.hitTestObject(characterMC)) 
     { 
      trace("Hit an enemy"); 
      MovieClip(root).updateScores(this); 
      setPosition(); 
     }//end if statement 
    }//end function checkCollision 
    //function to remove enemies from map 
    public function removeAsset():void 
    { 
     // remove event listeners and the item 
     removeEventListener(Event.ENTER_FRAME, checkCollision); 
     //removeEventListener(Event.ENTER_FRAME, moveEnemy); 
     this.parent.removeChild(this); 
     trace("removing the enemies"); 
    }//end function removeAsset 
}//end class 
}//end package 

Itemクラスのコード（汚いコードを事前に

謝罪は、私はちょうどAS3

ゲームのドキュメントクラスのコードを使用して開始しました収集する）

package 
{ 

import flash.events.Event; 
import flash.events.MouseEvent; 
import flash.display.MovieClip; 
import flash.geom.Rectangle; 

public class collect extends MovieClip 
{ 

    private var itemNum:int; 
    private var borderCollect:Rectangle; 
    private var frameNum:int; 
    private var characterMC:MovieClip; 
    public var healthMod:int; 
    public var scoreMod:int; 

    public function collect(myBorder:Rectangle, mySkill:int, player:MovieClip) 
    { 
     borderCollect = new Rectangle(30,180,870,750); 
     characterMC = player; 
     healthMod = 0; 
     scoreMod = 1; 
     //constructor code 
     trace("Initialise an Item"); 
     //constraint area for item spawn 
     var borderCollect = myBorder; 
     var offset = -200; 
     //which item is spawned - based on the player skill variable 
     var itemNum = Math.ceil(Math.random() * mySkill); 
     var frameNum = Math.ceil(Math.random() * 3); 
     //start process once item appears on stage 
     addEventListener(Event.ADDED_TO_STAGE,initItem); 
     addEventListener(Event.ENTER_FRAME, checkItems); 
    }//public function "collect" end, what is initiated by the class 

    private function initItem(evt:Event):void 
    { 
     //display frame based on itemNum 
     gotoAndStop(frameNum); 
     trace("selecting item frames"); 
     //tun position item function 
     setPosition(); 
     trace("setting item positions"); 
     //remove no longer needed event listener 
     removeEventListener(Event.ADDED_TO_STAGE,initItem); 
    }//function initItem end 

    private function setPosition():void 
    { 
     var myBorder = new Rectangle(50,180,800,500); 
     var offset = 100; 
     //positioning the Item according to borders 
     trace("setting positions for items"); 
     var myWidth:int = myBorder.right - myBorder.left - offset; 
     this.x = Math.ceil(Math.random() * myWidth) + myBorder.left * 1; 
     var myHeight:int = myBorder.bottom - myBorder.top - offset; 
     this.y = Math.ceil(Math.random() * myHeight) + myBorder.top * 1; 
    }//function setPosition end 

    private function checkItems(evt: Event):void 
    { 
     // hit the character 
     if (this.hitTestObject(characterMC)) 
     { 
      trace("Got an Item"); 
      MovieClip(root).updateScores(this); 
      removeAsset(); 
     }//end if statement 
    }//end function checkCollision 

    public function removeAsset():void 
    { 
     // remove event listeners and the item 
     removeEventListener(Event.ENTER_FRAME, checkItems); 
     this.parent.removeChild(this); 
     trace("removing an Item"); 
    }//end function removeMe 

}//class end 

}//package end 

エラー（収集されたアイテムとゲームオーバー）

TypeError: Error #1009: Cannot access a property or method of a null object reference. 
at collect/removeAsset()[H:\DIG MEDIA Post CHris\Memento - items added\collect.as:77] 
at Memento/clearObjects()[H:\DIG MEDIA Post CHris\Memento - items added\Memento.as:140] 
at Memento/gameOver()[H:\DIG MEDIA Post CHris\Memento - items added\Memento.as:165] 
at Memento/updateScores()[H:\DIG MEDIA Post CHris\Memento - items added\Memento.as:111] 
at enemy/checkCollision()[H:\DIG MEDIA Post CHris\Memento - items added\enemy.as:113] 

のaddItem、addEnemy、addItemsなども代わりに、文書クラスのボタンに接続された.FLAフレームに配置されます。私はそれが悪い習慣だと知っていますが、彼らは始めからそこにいました。私はそれらを動かそうとしたときに多くの問題を引き起こしました。

いずれにせよ、私が作った（おそらく非常に愚かな）間違いを見つけるために私の（ひどく整形された）コードを見て喜んでくれる誰にも感謝しています。また、私はどこが間違っているのか分かりません。

Answer 1

なぜ私のソリューションがうまく機能しているのかを詳しく調べる必要があります。その本質は次のとおりです。ある時点で、削除しようとしている要素が存在しないか、親にもう接続されていないかのいずれかです。このコードは、削除しようとしているインスタンスが存在し、親を持っていることを保証します

if (this.parent) this.parent.removeChild(this);