as3画圆类错误

Question

I am trying to create an event listener in a custom class. I have seen this in books but I get error "Access of undefined property on MouseDown". I have tried to abstract the issue as much as possible. The command I am using to call my class is provided below. Thanks for any insights.

package  
{
import flash.display.*;;
import flash.events.*;;

public class MouseDraw extends Sprite {

    public function MouseDraw() {
        addEventListener(MouseEvent.MOUSE_DOWN, onMouseDown);        
        }


    public function OnMouseDown(event:MouseEvent):void {
        trace("mouse down");        
    }                   

}   

}

//code in fla

var mouseDraw:MouseDraw= new MouseDraw();
addChild(mouseDraw);

Answer 1

There is a typo in your code: the name of your handler ( OnMouseDown() ) begins with a capital letter, but you add an event listener on onMouseDown with a lower case. Rename your function to onMouseDown and it should work.

Answer 2

wow--got this to work after mad googling. thanks all who commented. Moral of the story--dont believe the code you see in books will compile!

package  
{
import flash.display.*;;
import flash.events.*;;

public class MouseDraw extends Sprite {

    public function MouseDraw() {

        graphics.lineStyle(1);

        addEventListener(Event.ADDED_TO_STAGE, init);                       
        }


    private function init(e:Event):void {
        stage.addEventListener(MouseEvent.MOUSE_DOWN,  onMouseDown);                    
    }

    private function onMouseDown(event:MouseEvent):void {
        trace("mouse down");        
    }                   

}   

}