游戏专用的stage按键监听

package tools{
public class KeyIsDown{
private static var obj;

public static function init(stage){
obj = new Object();
stage.addEventListener("keyDown", keydownHandler);
stage.addEventListener("keyUp", keyupHandler);
}

public static function isDown(key){
return(obj[key] ? true : false);
}

private static function keydownHandler(event){
obj[event.keyCode] = true;
}

private static function keyupHandler(event){
obj[event.keyCode] = false;
}

}
}