Question

I’m new to Actionscript 3 and I’m wanting to allow a circle to move down using the down arrow on the keyboard. Here’s my code:

package  {

import flash.display.MovieClip;
import flash.events.KeyboardEvent;
import flash.ui.Keyboard;

public class Circle extends MovieClip {

    public function Circle() {
        // constructor code
        var speed:int = 3;

        addEventListener(KeyboardEvent.KEY_DOWN,keyIsDown);

        function keyIsDown(event:KeyboardEvent) {
            if(event.keyCode == Keyboard.DOWN) {
                y = y+=speed;
            }
        }
    }

}

}

When I test it, nothing happens when I press the down key. Anyone know what’s wrong with the code?

Answer 1

Try adding KeyBoard events to the stage instead of to the class. Additionally, I would not nest functions like that, bad practice in general. Also the line y = y+=speed; is confusing, shouldn’t it just be y += speed; ?

EDIT: Sorry, I guess stage will be null in the constructor, I’ve added a ADDED event listener.

Try this:

package  {

    import flash.display.MovieClip;
    import flash.events.Event;
    import flash.events.KeyboardEvent;
    import flash.ui.Keyboard;

    public class Circle extends MovieClip {

        public function Circle() {
            // constructor code
            var speed:int = 3;

            addEventListener(Event.ADDED, onAdded);        
        }

        private function onAdded(event:Event) {
            stage.addEventListener(KeyboardEvent.KEY_DOWN,keyIsDown);
        }

        private function keyIsDown(event:KeyboardEvent) {
            if(event.keyCode == Keyboard.DOWN) {
                 y += speed;
            }
        }

    }
}