不知道哪位有做过cocos2dx 3.0 多点触摸缩放，有参考http://blog.csdn.net/somestill/article/details/10581277的来实现，但在onTouchesBegan事件里一直只会捕到一个触点。
现在的实现方式是在onTouchesMoved里计算触摸前后两点距离算缩放比。但使用起来很不自然
auto listener = EventListenerTouchAllAtOnce::create();
listener->onTouchesBegan = CC_CALLBACK_2(WorldLayer::onTouchesBegan, this);
listener->onTouchesMoved = CC_CALLBACK_2(WorldLayer::onTouchesMoved, this);
listener->onTouchesEnded = CC_CALLBACK_2(WorldLayer::onTouchesEnded, this);
_eventDispatcher->addEventListenerWithSceneGraphPriority(listener, sprite);
void WorldLayer::onTouchesBegan(const std::vector& touches, Event *event)
{
//查看日志,在多点触摸时，只有一个点
log("world map touches began: size=%d", touches.size() );
}
void WorldLayer::onTouchesMoved(const std::vector& touches, Event *event)
{
//缩放
if(touches.size() > 1)
{
auto distance1 = touches->getPreviousLocation().distance(touches->getPreviousLocation());
auto distance2 = touches->getLocation().distance(touches->getLocation());
float scale = sprite->getScale() * ( distance2 / distance1);
scale = MIN(2,MAX(0.5, scale));
sprite->setScale(scale);
log("world map touches moved: size=%d, d1=%f , d2=%f",touches.size() , distance1,distance2 );
}
else
{
//移动地图
onTouchMoved(touches,event);
}
}
void WorldLayer::onTouchesEnded(const std::vector& touches, Event* event)
{
log("world map touches ended: size=%d", touches.size() );
}
```