Flex ActionScript实例代码 在一个特定的方向移动对象

package {
    import flash.display.Sprite;
    import flash.events.Event;
    import flash.events.TimerEvent;
    import flash.utils.Timer;

    public class Main extends Sprite {
        private var _sprite:Sprite = new Sprite(  );
        private var _angle:Number = 135;
        private var _speed:Number = 4;
        private var _timer:Timer;

        public function Main (  ) {
            _sprite.graphics.beginFill(0x0000ff, 100);
            _sprite.graphics.drawCircle(0, 0, 5);
            _sprite.graphics.endFill(  );
            _sprite.x = 300;
            _sprite.y = 100;
            addChild(_sprite);
            _timer = new Timer(3);
            _timer.addEventListener("timer", onTimer);
            _timer.start(  );
        }

        public function onTimer(event:TimerEvent):void {
            var radians:Number = _angle * Math.PI / 180;
            var vx:Number = Math.cos(radians) * _speed;
            var vy:Number = Math.sin(radians) * _speed;
            _sprite.x += vx;
            _sprite.y += vy;
        }
    }
}