在定義的對象上執行“ hitTest”時，為什么會收到空錯誤？

Question

我要做的就是從舞台上刪除一些孩子，但是卻給了我一個空錯誤：

TypeError: Error #2007: Parameter hitTestObject must be non-null.
at flash.display::DisplayObject/flash.display:DisplayObject::_hitTest()
at flash.display::DisplayObject/hitTestObject()
at SpaceOddessey_fla::MainTimeline/GreenMove()

我不明白為什么會這樣，因為我在“ Green Guy”的移動/刪除功能上方的功能中定義了對象。 在修復此項目之前，我無法繼續進行該項目，因為我還需要將其用於其余的精靈。

這是我的代碼

stop();

//do this three times (for each space dude)
//GREEN
var MaxGreen:int = 1;
//Here we declare the speed of these cannon balls
var GreenVelocityX:Array = new Array();
var GreenVelocityY:Array = new Array();
//keep track of how many green guys
var GreenCount:int = 0;
var GreenSprite:Sprite;//declare a global variable for the cannonBall sprite.
var theGreen:Green_Guy;
//create the array thats holds the green guys
var myGreenGuyArray:Array = new Array(); 



//YELLOW
var MaxYellow:int = 1;
//Here we declare the speed of these cannon balls
var YellowVelocityX:Array = new Array();
var YellowVelocityY:Array = new Array();
//keep track of how many yellow guys
var YellowCount:int = 0;
var YellowSprite:Sprite;//declare a global variable for the cannonBall sprite.
var theYellow:Yellow_Guy;
//create the array thats holds the yellow guys
var myYellowGuyArray:Array = new Array();



//BABY
var MaxBabies:int = 1;
//Here we declare the speed of these cannon balls
var BabyVelocityX:Array = new Array();
var BabyVelocityY:Array = new Array();
//keep track of how many baby guys
var BabyCount:int = 0;
var BabySprite:Sprite;//declare a global variable for the cannonBall sprite.
var theBaby:Baby_Guy;
//create the array thats holds the baby guys
var myBabyGuyArray:Array = new Array();



//SPACE SHIP
var MaxShips:int = 4;
//Here we declare the speed of these cannon balls
var ShipVelocityX:Array = new Array();
var ShipVelocityY:Array = new Array();
//keep track of how many baby guys
var ShipCount:int = 0;
var ShipSprite:Sprite;//declare a global variable for the cannonBall sprite.
var theShip:space_ship;
//create the array thats holds the baby guys
var ShipArray:Array = new Array();


//ASTEROID
var MaxRocks:int = 6;
//Here we declare the speed of these cannon balls
var RockVelocityX:Array = new Array();
var RockVelocityY:Array = new Array();
//keep track of how many baby guys
var RockCount:int = 0;
var RockSprite:Sprite;//declare a global variable for the cannonBall sprite.
var theRock:rock;
//create the array thats holds the baby guys
var RockArray:Array = new Array();

yellow_btn.addEventListener(MouseEvent.CLICK, ClickHandle);
green_btn.addEventListener(MouseEvent.CLICK, ClickHandle);
baby_btn.addEventListener(MouseEvent.CLICK, ClickHandle);
function ClickHandle(targetEvent:MouseEvent):void
{
    if(targetEvent.target == yellow_btn)
    {
        MaxYellow += 1;

        stage.addEventListener(Event.ENTER_FRAME,makeYellow);
    }
    else if(targetEvent.target == green_btn)
    {
        MaxGreen += 1;
        stage.addEventListener(Event.ENTER_FRAME,makeGreen);
    }
    else if(targetEvent.target == baby_btn)
    {
        MaxBabies += 1;
        stage.addEventListener(Event.ENTER_FRAME,makeBaby);
    }
}

stage.addEventListener(Event.ENTER_FRAME,makeShips);

function makeShips(Space:Event){
    //Create the Enemies if there are less then 100
    if (ShipCount < MaxShips){
        //create our sprites
        ShipSprite = new Sprite();
        stage.addChild(ShipSprite);
        theShip = new space_ship();
        ShipSprite.addChild(theShip);

        ShipSprite.x = Math.random() * 500;//width ~ 81.7
        ShipSprite.y = Math.random() * 300;

        //allows a scaler of making objects from big to small
        //BabySprite.scaleX = BabySprite.scaleY = Math.random() * 1.3;

        ShipArray[ShipCount] = ShipSprite;
        ShipCount += 1;

        stage.addEventListener(Event.ENTER_FRAME,ShipMove);
        }

        //end for loop
    }
function ShipMove(go:Event):void
{
    for(var s=0; s<ShipCount; s++)
    {
        ShipVelocityX[s] = -3;
        ShipVelocityY[s] = -1;
        /*if(my)
        {

        }*/
        ShipArray[s].x += ShipVelocityX[s];
        //myYellowGuyArray[a].y += YellowVelocityY[a];
        if (ShipArray[s].x > 550)
        {
            ShipArray[s].x = 0 - ShipArray[s].width;
        }
        else if(ShipArray[s].x + ShipArray[s].width < 0)
        {
            ShipArray[s].x = 500;
        }
        if(ShipArray[s].y > 400)
        {
            ShipArray[s].y = 0 - ShipArray[s].height;
        }
        else if(ShipArray[s].y + ShipArray[s].height < 0)
        {
            ShipArray[s].y = 400;
        }
    }
}

stage.addEventListener(Event.ENTER_FRAME,makeBaby);

function makeBaby(DudeEvent:Event){
    //Create the Enemies if there are less then 100
    if (BabyCount < MaxBabies){
        //create our sprites
        BabySprite = new Sprite();
        stage.addChild(BabySprite);
        theBaby = new Baby_Guy();
        BabySprite.addChild(theBaby);

        BabySprite.x = Math.random() * 500;//width ~ 81.7
        BabySprite.y = Math.random() * 300;

        //allows a scaler of making objects from big to small
        //BabySprite.scaleX = BabySprite.scaleY = Math.random() * 1.3;

        myBabyGuyArray[BabyCount] = BabySprite;
        BabyCount += 1;
        //trace(myEnemies.length);

        stage.addEventListener(Event.ENTER_FRAME,BabyMove);
        }

        //end for loop
    }
function BabyMove(go:Event):void
{
    for(var i=0; i<BabyCount; i++)
    {
        BabyVelocityX[i] = 5;
        BabyVelocityY[i] = 2;
        /*if(my)
        {

        }*/
        myBabyGuyArray[i].x += BabyVelocityX[i];
        myBabyGuyArray[i].y += BabyVelocityY[i];
        myBabyGuyArray[i].rotation += 2;
        if (myBabyGuyArray[i].x > 550)
        {
            myBabyGuyArray[i].x = 0 - myBabyGuyArray[i].width;
        }
        else if(myBabyGuyArray[i].x + myBabyGuyArray[i].width < 0)
        {
            myBabyGuyArray[i].x = 500;
        }
        if(myBabyGuyArray[i].y > 400)
        {
            myBabyGuyArray[i].y = 0 - myBabyGuyArray[i].height;
        }
        else if(myBabyGuyArray[i].y + myBabyGuyArray[i].height < 0)
        {
            myBabyGuyArray[i].y = 400;
        }
        for(var v:int=0; v<RockCount; v++)
        {
            if(RockArray[v].hitTestObject(myBabyGuyArray[i]))
            {
                //trace('hey')
                BabyVelocityX[i] = 100;
            }
        }
    }
}

stage.addEventListener(Event.ENTER_FRAME,makeYellow);

function makeYellow(Dude:Event){
    //Create the Enemies if there are less then 100
    if (YellowCount < MaxYellow){
        //create our sprites
        YellowSprite = new Sprite();
        stage.addChild(YellowSprite);
        theYellow = new Yellow_Guy();
        YellowSprite.addChild(theYellow);

        YellowSprite.x = Math.random() * 500;//width ~ 81.7
        YellowSprite.y = Math.random() * 300;

        //allows a scaler of making objects from big to small
        //BabySprite.scaleX = BabySprite.scaleY = Math.random() * 1.3;

        myYellowGuyArray[YellowCount] = YellowSprite;
        YellowCount += 1;

        stage.addEventListener(Event.ENTER_FRAME,YellowMove);
        }

        //end for loop
    }
function YellowMove(go:Event):void
{
    for(var a=0; a<YellowCount; a++)
    {
        YellowVelocityX[a] = -3;
        YellowVelocityY[a] = -1;
        /*if(my)
        {

        }*/
        myYellowGuyArray[a].x += YellowVelocityX[a];
        myYellowGuyArray[a].y += YellowVelocityY[a];
        myYellowGuyArray[a].rotation += 1;
        if (myYellowGuyArray[a].x > 550)
        {
            myYellowGuyArray[a].x = 0 - myYellowGuyArray[a].width;
        }
        else if(myYellowGuyArray[a].x + myYellowGuyArray[a].width < 0)
        {
            myYellowGuyArray[a].x = 500;
        }
        if(myYellowGuyArray[a].y > 400)
        {
            myYellowGuyArray[a].y = 0 - myYellowGuyArray[a].height;
        }
        else if(myYellowGuyArray[a].y + myYellowGuyArray[a].height < 0)
        {
            myYellowGuyArray[a].y = 400;
        }
        for(var u:int=0; u<RockCount; u++)
        {
            if(RockArray[u].hitTestObject(myYellowGuyArray[a]))
            {
                YellowVelocityX[a] *= -1;
            }
        }
    }
}

stage.addEventListener(Event.ENTER_FRAME,makeGreen);

function makeGreen(Evnt:Event){
    //Create the Enemies if there are less then 100
    if (GreenCount < MaxGreen){
        //create our sprites
        GreenSprite = new Sprite();
        stage.addChild(GreenSprite);
        theGreen = new Green_Guy();
        GreenSprite.addChild(theGreen);

        GreenSprite.x = Math.random() * 500;//width ~ 81.7
        GreenSprite.y = Math.random() * 300;

        //allows a scaler of making objects from big to small
        //BabySprite.scaleX = BabySprite.scaleY = Math.random() * 1.3;

        myGreenGuyArray[GreenCount] = GreenSprite;
        GreenCount += 1;

        stage.addEventListener(Event.ENTER_FRAME,GreenMove);
        }
        //end for loop
    }
function GreenMove(go:Event):void
{
    for(var b:int=0; b<GreenCount; b++)
    {
        GreenVelocityX[b] = 7;
        GreenVelocityY[b] = -4;

        myGreenGuyArray[b].x += GreenVelocityX[b];
        myGreenGuyArray[b].y += GreenVelocityY[b];
        myGreenGuyArray[b].rotation -= 1;
        if (myGreenGuyArray[b].x > 550)
        {
            myGreenGuyArray[b].x = 0 - myGreenGuyArray[b].width;
        }
        else if(myGreenGuyArray[b].x + myGreenGuyArray[b].width < 0)
        {
            myGreenGuyArray[b].x = 500;
        }
        if(myGreenGuyArray[b].y > 400)
        {
            myGreenGuyArray[b].y = 0 - myGreenGuyArray[b].height;
        }
        else if(myGreenGuyArray[b].y + myGreenGuyArray[b].height < 0)
        {
            myGreenGuyArray[b].y = 400;
        }
        for(var z:int=0; z<ShipCount; z++)
        {
            //if(myGreenGuyArray[b] == null)
            {
                if(ShipArray[z].hitTestObject(myGreenGuyArray[b]))
                {
                    //if(GreenCount > 1)
                    //{
                        myGreenGuyArray[b].y = -50;
                        stage.removeChild(myGreenGuyArray[b]);
                        myGreenGuyArray.splice(b,1);
                        GreenCount--;
                        //b--;
                    //}
                }
            }
        }
        for(var g:int=0; g<RockCount; g++)
        {
            if(RockArray[g].hitTestObject(myGreenGuyArray[b]))
            {
                GreenVelocityX[b] *= -1;
            }
        }
    }
}

stage.addEventListener(Event.ENTER_FRAME,makeRocks);

function makeRocks(RockHard:Event){
    //Create the Enemies if there are less then 100
    if (RockCount < MaxRocks){
        //create our sprites
        RockSprite = new Sprite();
        stage.addChild(RockSprite);
        theRock = new rock();
        RockSprite.addChild(theRock);

        RockSprite.x = Math.random() * 500;//width ~ 81.7
        RockSprite.y = Math.random() * 300;

        //allows a scaler of making objects from big to small
        //BabySprite.scaleX = BabySprite.scaleY = Math.random() * 1.3;

        RockArray[RockCount] = RockSprite;
        RockCount += 1;

        stage.addEventListener(Event.ENTER_FRAME,RockMove);
        }

        //end for loop
    }
function RockMove(go:Event):void
{
    for(var r=0; r<RockCount; r++)
    {
        RockVelocityX[r] = 7;
        RockVelocityY[r] = 3;
        /*if(my)
        {

        }*/
        RockArray[r].x += RockVelocityX[r];
        //RockArray[r].y += RockVelocityY[r];
        if (RockArray[r].x > 550)
        {
            RockArray[r].x = 0 - RockArray[r].width;
        }
        else if(RockArray[r].x + RockArray[r].width < 0)
        {
            RockArray[r].x = 500;
        }
        if(RockArray[r].y > 400)
        {
            RockArray[r].y = 0 - RockArray[r].height;
        }
        else if(RockArray[r].y + RockArray[r].height < 0)
        {
            RockArray[r].y = 400;
        }
    }
}

Answer 1

您必須重組和簡化代碼。 您必須不惜一切代價消除嵌套的enter_frame事件。 理想情況下，您可以通過一個ENTER_FRAME事件來完成所有事情。

請按照與您的代碼最接近但更干凈的方式執行以下操作

1. 創建制作和移動功能
2. 通過for循環調用make函數（而不是enter_frame）
3. 一旦所有make函數被調用，則創建一個enter_frame事件並在其中調用move函數。

但是，您可以進一步使它更清潔，但是至少要做到上述幾點，才能使您早日實現目標。

Answer 2

我不明白為什么會這樣

這聽起來微不足道，但這是由於錯誤描述中給出的原因而發生的：

參數hitTestObject必須為非null。

這是人們必須接受的真理。 沒有其他辦法了。 沒有“但我確定這不會發生”這樣的事情。 提出更好的論點並不能贏得討論。 從某種意義上說，編譯器總是正確的。 您不能反駁。

我在“ Green Guy”的移動/刪除功能上方的功能中定義了對象

不。該錯誤表明您沒有，所以您沒有。 該參數為null 。 否認事實是沒有意義的。

真正的問題不是“ 即使不是， 為什么也說它為null？ ”，而是“ 為什么值為null？ ”。

該錯誤表明它發生在hitTestObject()函數中。 堆棧跟蹤說明它發生在GreenMove()函數中。 有兩行可能會導致這種情況。

if(ShipArray[z].hitTestObject(myGreenGuyArray[b]))

和

if(RockArray[g].hitTestObject(myGreenGuyArray[b]))

您應該在每行放置一個斷點，再次使用調試器運行代碼，然后嘗試重現該錯誤。 這是調試代碼的方式。 您已經五個小時沒有看到它了，希望它會因您找不到原因而跳到您身上並感到沮喪。

發生錯誤時， hitTestObject會認為myGreenGuyArray[b]為null 。 由此，您知道b值是什么。 再次運行。 使它再次失敗。 查看它是否總是以相同的b值發生。

這行看起來很可疑，因為它改變了數組。

myGreenGuyArray.splice(b,1);

---

您的問題是由數組的混亂使用引起的。 想一想：如果只有一個元素被刪除怎么辦？ 如果再次訪問該數組的（已刪除，不存在）元素，會發生什么情況？

trace([1,2,3][37] == null); // does the result of accessing an element that doesn't exist equal null?

---

為了解決這個問題

1. 擺脫不必要的計數變量。 數組正是出於這個目的而具有length屬性。
2. 向后迭代數組。 如果一個元素被刪除並且不需要奇怪的計數減法來解決這個問題，這將防止跳過它，它就可以了。
3. 刪除元素后，立即停止循環並繼續執行下一個迭代（可能與標簽結合使用），以continue和/或break跳出嵌套循環。