Error #2007: Parameter child must be non-null.

[Pedz101]

Hello I am still a newbie at actionscript class. I have no idea on what's the error. If you can please help me that would be thankful. The error says:

TypeError: Error #2007: Parameter child must be non-null.
at flash.display: : DisplayObjectContainer/addChild()
at Movement/init()

package {
    import flash.display.MovieClip;
    import flash.events.Event;
    import flash.events.MouseEvent
    import Input;
    
    public class Movement extends MovieClip 
{
        
        public var square:MovieClip;
        public var start_btn:MovieClip
        
        private var _max:Number = 10;
        private var dx:Number = 0;
        private var dy:Number = 0;
        
            
        public function Movement():void 
        {
            this.stop();
            addEventListener(Event.ADDED_TO_STAGE, init);
        }
            
        private function init(e:Event):void {
            removeEventListener(Event.ADDED_TO_STAGE, init);
            
            //adding Childs
            addChild(square);
            addChild(start_btn);
            
            
            //Initialize the Input.as Class with handler on stage
            Input.initialize(stage);
            
            //Add Events Listeners
            addEventListener(Event.ENTER_FRAME, refresh);
            start_btn.addEventListener(MouseEvent.CLICK, startingGame);
        }
        
        private function refresh(e:Event):void {
            //Key Handler
            if (Input.kd("A", "LEFT")) {
                dx = dx < 1 - _max ? _max * -1 : dx - 1;
            }
            if (Input.kd("D", "RIGHT")) {
                dx = dx > _max - 1 ? _max : dx + 1;
            }
            
            if (!Input.kd("A", "LEFT", "D", "RIGHT")) {
                if (dx > 1) {
                    dx = dx < 1 ? 0 : dx - 1;
                } else {
                    dx = dx > -1 ? 0 : dx + 1;
                }
            }
            
            if (Input.kd("W", "UP")) {
                dy = dy < 1 - _max ? _max * -1 : dy - 1;
            }
            if (Input.kd("S", "DOWN")) {
                dy = dy > _max - 1 ? _max : dy + 1;
            }
            
            if (!Input.kd("W", "UP", "S", "DOWN")) {
                if (dy > 1) {
                    dy = dy < 1 ? 0 : dy - 1;
                } else {
                    dy = dy > -1 ? 0 : dy + 1;
                }
            }
            
            //Margin detection
            if (square.x - dx < -dx || square.x + dx + square.width > stage.stageWidth) {
                //x axis detection
                square.x = square.x - dx < -dx ? 0 : stage.stageWidth - square.width;
                dx *= -1;
            }
             
            if (square.y - dy < -dy || square.y + dy + square.height > stage.stageHeight) {
                //y axis detection
                square.y = square.y - dy < -dy ? 0 :  stage.stageHeight - square.height;
                dy *= -1;
            }
            
            //Apply the dynamic variables
            square.x += dx;
            square.y += dy;
        }
        
        public function startingGame(e:MouseEvent):void
        {
            gotoAndStop(2);
        }
    }
    
}

[thawfeek_yahya]

Welcome to the forum.

you should initialize the movie clip before using it

ie)

public var square:MovieClip = new MovieClip();
public var start_btn:MovieClip = new MovieClip();

[santanoa]

Welcome,

(EDIT: First suggestion already mentioned
resuming post...
)


If you're trying to refer to mcs you put in this class from Flash, you have to name them in Flash in order to be able to access them. Then you can just write

//adding Childs
addChild(square);
addChild(start_btn);

IMPORTANT: if this is true, you should not be declaring

public var square:MovieClip;
public var start_btn:MovieClip

in your class, because this will actually override your mcs' variables and you won't be able to access them


Hope something i wrote made sense

[[afz]snickelfitz]

Post the Input class.
I have no idea what the following statement actually means.

//Initialize the Input.as Class with handler on stage
Input.initialize(stage);

[Pedz101]

@thawfeek_yahya:
Thanks worked out perfectly

@santanoa:
Thanks for the advice