今天在游戏中加了个战斗数值显示，其中就有用到渐变的效果，发现竟然没有生效，查看了源代码发现子节点的opacity值跟随父节点的opacity更新是有前提的，那就是这货：_cascadeOpacityEnabled。请看源代码：

void Node::setOpacity(GLubyte opacity)
{
    _displayedOpacity = _realOpacity = opacity;
    
    updateCascadeOpacity();
}

void Node::updateCascadeOpacity()
{
    GLubyte parentOpacity = 255;
    
    if (_parent != nullptr && _parent->isCascadeOpacityEnabled())
    {
        parentOpacity = _parent->getDisplayedOpacity();
    }
    
    updateDisplayedOpacity(parentOpacity);
}

void Node::updateDisplayedOpacity(GLubyte parentOpacity)
{
    _displayedOpacity = _realOpacity * parentOpacity/255.0;
    updateColor();
    
    if (_cascadeOpacityEnabled)
    {
        for(const auto& child : _children)
        {
            child->updateDisplayedOpacity(_displayedOpacity);
        }
    }
}

void Node::setCascadeOpacityEnabled(bool cascadeOpacityEnabled)
{
    if (_cascadeOpacityEnabled == cascadeOpacityEnabled)
    {
        return;
    }
    
    _cascadeOpacityEnabled = cascadeOpacityEnabled;
    
    if (cascadeOpacityEnabled)
    {
        updateCascadeOpacity();
    }
    else
    {
        disableCascadeOpacity();
    }
}