Question

TypeError: Error #1009: Cannot access a property or method of a null object reference.
at Main_fla::MainTimeline/BulletFire()[Main_fla.MainTimeline::frame32:68]. Is occurring and I have no idea why…PLEASE HELP, it has been days of me troubleshooting this and i am completely lost. Thanks, also, for some reason when I fire the bullet it only goes at 45 degrees and 225 degrees…Thanks guys

    //Create an array to hold multiple sprites
var mySpriteHolder:Array = [];
//Create a counter to keep track of the number of sprites
var lbCounter:int = 0;
//Maximum number of sprites on the canvas
var maxLB:int = 1;
//Keypress Code
stage.addEventListener(MouseEvent.CLICK, dropBullet);
//Function for the mouse event to fire bullet
function dropBullet(evt:MouseEvent):void{

     var bcos:Number = Math.cos((Turret.rotation) * Math.PI / 180);
     var bsin:Number = Math.sin((Turret.rotation) * Math.PI / 180);

     //starting x and y
     var startx:Number = Turret.x + (15 * bcos);
     var starty:Number = Turret.y + (15 * bsin);

    //calculates where the bullet needs to go by aiming in front of the gun
    var endx:Number = Turret.x + (50 * bcos);
    var endy:Number = Turret.y + (50 * bsin);

    var Bullet:MovieClip = new bullet();

    Bullet.x = startx;
    Bullet.y = starty;

    Bullet.xspeed = (endx - startx)/5;
    Bullet.yspeed =  (endx - startx)/5;

    mySpriteHolder.push(Bullet);
    stage.addChild(Bullet);

    //this calls the move down function
    stage.addEventListener(Event.ENTER_FRAME,BulletFire);
}
//Function to shoot bullet
function BulletFire(evt:Event):void{
    var Bullet:MovieClip;
    //Use a for loop to move the Bullets
    for(var i:int=0; i<=mySpriteHolder.length; i++){
        Bullet = mySpriteHolder[i];
    //Bounds Collision
    if(Bullet.hitTestObject(Up)){
        Bullet.yspeed*=-1;
    }
    if(Bullet.hitTestObject(Lower)){
        Bullet.yspeed*=-1;
    }
    if(Bullet.hitTestObject(Left)){
        Bullet.xspeed*=-1;
    }
    if(Bullet.hitTestObject(Right)){
        Bullet.xspeed*=-1;
    }
    //Blockade Collision
    for(var t in myBlockadeHolder){
            if(Bullet.hitTestObject(myBlockadeHolder[t])){
                trace("test");
            }
        }
    //Target Collision
        for(var c in mytargetHolder){
            if(Bullet.hitTestObject(mytargetHolder[c])){
            stage.removeChild(Bullet);
            mySpriteHolder.splice(i,1);
            lbCounter --;
            mytargetHolder[c].y = Math.random()*390 + 10;
            mytargetHolder[c].x = Math.random()*390 + 10;
                while(mytargetHolder[c].hitTestObject(Turret)){
                    mytargetHolder[c].y = Math.random()*390 + 10;
                    mytargetHolder[c].x = Math.random()*390 + 10;
                }
            }
            for(var a in mytargetHolder){
                for(var s in mytargetHolder){
                    while(mytargetHolder[a].hitTestObject(mytargetHolder[s])&& a!=s){
                        mytargetHolder[a].y = Math.random()*390 + 10;
                        mytargetHolder[a].x = Math.random()*390 + 10;
                    }
                }
                for(var g in myBlockadeHolder){
                    while(mytargetHolder[a].hitTestObject(myBlockadeHolder[g])&& a!=g){
                        mytargetHolder[a].y = Math.random()*390 + 10;
                        mytargetHolder[a].x = Math.random()*390 + 10;
                    }
                }
            }
        }
        Bullet.y += Bullet.yspeed;
        Bullet.x += Bullet.xspeed;
    }
}

Answer 1

mySpriteHolder.splice(i,1);

This line is probably causing some unexpected results (and possibly your error) as you’re splicing objects from the array your loop is working incrementally from. It’s important to understand that when you splice an object in AS3 you’re effectively removing that element and all indices that follow move down the splicing amount. Try working backwards in the loop instead:

 for(var i:int=mySpriteHolder.length-1; i>=0; i--){

Also, this line should be moved out of your MouseClick Event as you’re adding multiple ENTER_FRAME events every time a bullet is placed. As it is right now it’s going to do an additional bulletFire() pass every time you mouse click:

stage.addEventListener(Event.ENTER_FRAME,BulletFire);