cocos2d-x学习耗时点备忘之二——嵌套Sprite的boundingBox位置校正备忘

     在cocos2d-x中，常通过Sprite的boundingBox()方法来获取该Sprite的边框，这个边框最常用的用途就是做为碰撞框了。但是如果你在一个Sprite（比如A）中通过addChild加入一个子Sprite（比如B），则B通过boundingBox()获取到的边框，比如boundingBox_B相对于父Layer来说，位置是不准的，这会导致明明按中了B，却得不到该有的响应。

     一个校正的代码如下，首先是加入子Sprite的方法：

StartPanel::StartPanel() {

	initWithFile("startpage.png");

	CCDirector *pDirector = CCDirector::sharedDirector();
	CCSize winSize = pDirector->getWinSize();
	float screenWidth = winSize.width;
	float screenHeight = winSize.height;

	CCSize backgroundSize = this->getContentSize();
	backgroundWidth = backgroundSize.width;
	backgroundHeight = backgroundSize.height;
	scaleX = screenWidth / backgroundWidth;
	scaleY = screenHeight / backgroundHeight;

	this->setScaleX(scaleX);
	this->setScaleY(scaleY);

	this->setPosition(ccp(screenWidth * 0.5f, screenHeight * 0.5f));

	play = CCSprite::spriteWithFile("play.png");

	float scaleDuration = 1.0f;
	CCScaleBy* bigScale = CCScaleBy::actionWithDuration(scaleDuration, 2.0f);
	CCScaleBy* smallScale = CCScaleBy::actionWithDuration(scaleDuration, 0.5f);
	CCSequence* scaleSequence = CCSequence::actionOneTwo(bigScale, smallScale);
	CCRepeatForever* scaleForever = CCRepeatForever::actionWithAction(scaleSequence);
	play->runAction(scaleForever);

	play->setPosition(ccp(backgroundWidth * 0.5f, backgroundHeight * 0.3f));
	this->addChild(play);
}

其中StartPanel本身是一个Sprite，然后加入了Play这个子Sprite，同时StartPanel和Play都进行了自身的缩放（Play是一个实时的缩放动画）。则Play的boundingBox()的校正代码如下：

CCRect StartPanel::getPlayBoundingBox() {
	if(play != NULL) {
		CCRect oldBoundingBox = play->boundingBox();

		float offsetX = this->getPosition().x - backgroundWidth * 0.5f * scaleX;
		float offsetY = this->getPosition().y - backgroundHeight * 0.5f * scaleY;

		CCRect newBoundingBox = CCRectMake(oldBoundingBox.origin.x * scaleX + offsetX, oldBoundingBox.origin.y * scaleY + offsetY, oldBoundingBox.size.width * scaleX, oldBoundingBox.size.height * scaleY);
		return newBoundingBox;
	} else {
		return CCRectZero;
	}
}

 效果图如下：

完毕，特此记录。