回転させたいオブジェクトの中心にある基準点を中心に回転します。
Yahoo Astraには、このようなもののためのDynamic Registrationクラスがあります。
これは次のように実装できます。
package
{
import com.yahoo.astra.utils.DynamicRegistration;
import flash.display.MovieClip;
import flash.events.Event;
import flash.geom.Point;
public class Bullet extends MovieClip
{
private var mc:MovieClip;
private var currentRotation:uint = 0;
public function Bullet()
{
mc = new MovieClip();
mc.graphics.beginFill(0);
mc.graphics.drawRect(120, 120, 40, 40);
mc.graphics.endFill();
addChild(mc);
addEventListener(Event.ENTER_FRAME, onEnterFrame);
}
private function onEnterFrame(e:Event):void
{
currentRotation = (currentRotation + 10) % 360;
DynamicRegistration.rotate(mc, new Point(140, 140), currentRotation);
}
}
}
Yahoo アストラ DynamicRegistration クラス:
/*
Copyright (c) 2008 Yahoo! Inc. All rights reserved.
The copyrights embodied in the content of this file are licensed under the BSD (revised) open source license
*/
package com.yahoo.astra.utils
{
import flash.geom.Point;
import flash.display.DisplayObject;
/**
* Allows you to manipulate display objects based on a registration point other
* than the standard (0,0).
*
* @author Josh Tynjala
*/
public class DynamicRegistration
{
/**
* Moves a <code>DisplayObject</code> to a new position (x,y) based on a registration point. The
* true position of the object will be (x - registration.x, y - registration.y).
*
* @param target the DisplayObject to move
* @param registration the registration point of the DisplayObject
* @param x the new x position, in pixels
* @param y the new y position, in pixels
*/
public static function move(target:DisplayObject, registration:Point, x:Number = 0, y:Number = 0):void
{
//generate the location of the registration point in the parent
registration = target.localToGlobal(registration);
registration = target.parent.globalToLocal(registration);
//move the target and offset by the registration point
target.x += x - registration.x;
target.y += y - registration.y;
}
/**
* Rotates a <code>DisplayObject</code> based on a registration point.
*
* @param target the DisplayObject to move
* @param registration the registration point of the DisplayObject
* @param rotation the new rotation angle
*/
public static function rotate(target:DisplayObject, registration:Point, degrees:Number = 0):void
{
changePropertyOnRegistrationPoint(target, registration, "rotation", degrees);
}
/**
* Scales a <code>DisplayObject</code> based on a registration point.
*
* @param target the DisplayObject to move
* @param registration the registration point of the DisplayObject
* @param scaleX the new x scaling factor
* @param scaleY the new y scaling factor
*/
public static function scale(target:DisplayObject, registration:Point, scaleX:Number = 0, scaleY:Number = 0):void
{
changePropertyOnRegistrationPoint(target, registration, "scaleX", scaleX);
changePropertyOnRegistrationPoint(target, registration, "scaleY", scaleY);
}
/**
* @private
* Alters an arbitary property based on the registration point.
*
* @param target the DisplayObject to move
* @param registration the registration point of the DisplayObject
* @param propertyName the property to change
* @param value the new value of the property to change
*/
private static function changePropertyOnRegistrationPoint(target:DisplayObject, registration:Point, propertyName:String, value:Number):void
{
//generate the location of the registration point in the parent
var a:Point = registration.clone();
a = target.localToGlobal(a);
a = target.parent.globalToLocal(a);
target[propertyName] = value;
//after the property change, regenerate the location of the registration
//point in the parent
var b:Point = registration.clone();
b = target.localToGlobal(b);
b = target.parent.globalToLocal(b);
//move the target based on the difference to make it appear the change
//happened based on the registration point
target.x -= b.x - a.x;
target.y -= b.y - a.y;
}
}
}