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cocos2d x 3.3 007 核心概念和相关类 节点
David edited this page Jan 14, 2015
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- 继承自Ref
- 来自代码的详细说明
Node is the base element of the Scene Graph. Elements of the Scene Graph must be Node objects or subclasses of it.
The most common Node objects are: Scene, Layer, Sprite, Menu, Label.
The main features of a Node are:
- They can contain other Node objects (`addChild`, `getChildByTag`, `removeChild`, etc)
- They can schedule periodic callback (`schedule`, `unschedule`, etc)
- They can execute actions (`runAction`, `stopAction`, etc)
Subclassing a Node usually means (one/all) of:
- overriding init to initialize resources and schedule callbacks
- create callbacks to handle the advancement of time
- overriding `draw` to render the node
Properties of Node:
- position (default: x=0, y=0)
- scale (default: x=1, y=1)
- rotation (in degrees, clockwise) (default: 0)
- anchor point (default: x=0, y=0)
- contentSize (default: width=0, height=0)
- visible (default: true)
Limitations:
- A Node is a "void" object. If you want to draw something on the screen, you should use a Sprite instead. Or subclass Node and override `draw`.
- zOrder scale position skew rotation AnchorPoint ContentSize ...
- set get
- set get
- get set
- get set
- set remove
- add remove get sort
- isRunning onEnter onEnterTransitionDidFinish onExit onExitTransitionDidStart cleanup
- draw visit
- runAction stopAction stopAllActions stopActionByTag getActionByTag
- setScheduler getScheduler scheduleUpdate scheduleUpdateWithPriority unscheduleUpdate schedule scheduleOnce unschedule unscheduleAllCallbacks update resume pause
- convertToNodeSpace convertToWorldSpace convertTouchToNodeSpace
- setPhysicsBody getPhysicsBody removeFromPhysicsWorld
* opengl/物理引擎相关的略过
1. 构造函数
Node::Node(void)
: _rotationX(0.0f)
//略过初始化列表
{
//导演的几个骨干业务员跑来兼职了
// set default scheduler and actionManager
Director *director = Director::getInstance();
//动作管理器
_actionManager = director->getActionManager();
_actionManager->retain();
//调度器
_scheduler = director->getScheduler();
_scheduler->retain();
//事件分发器
_eventDispatcher = director->getEventDispatcher();
_eventDispatcher->retain();
#if CC_ENABLE_SCRIPT_BINDING
ScriptEngineProtocol* engine = ScriptEngineManager::getInstance()->getScriptEngine();
_scriptType = engine != nullptr ? engine->getScriptType() : kScriptTypeNone;
#endif
_transform = _inverse = _additionalTransform = Mat4::IDENTITY;
}
2. 看看cleanup是怎么进行扫尾工作的
void Node::cleanup()
{
//停止所有动作和调度器回调
// actions
this->stopAllActions();
this->unscheduleAllCallbacks();
#if CC_ENABLE_SCRIPT_BINDING
if ( _scriptType != kScriptTypeNone)
{
int action = kNodeOnCleanup;
BasicScriptData data(this,(void*)&action);
ScriptEvent scriptEvent(kNodeEvent,(void*)&data);
ScriptEngineManager::getInstance()->getScriptEngine()->sendEvent(&scriptEvent);
}
#endif // #if CC_ENABLE_SCRIPT_BINDING
//遍历每一个child对象执行cleanup
// timers
for( const auto &child: _children)
child->cleanup();
}
3.add child
/* "add" logic MUST only be on this method
* If a class want's to extend the 'addChild' behavior it only needs
* to override this method
*/
void Node::addChild(Node *child, int localZOrder, int tag)
{
CCASSERT( child != nullptr, "Argument must be non-nil");
CCASSERT( child->_parent == nullptr, "child already added. It can't be added again");
addChildHelper(child, localZOrder, tag, "", true);
}
void Node::addChildHelper(Node* child, int localZOrder, int tag, const std::string &name, bool setTag)
{
if (_children.empty())
{
//分配空间
this->childrenAlloc();
}
//插入
this->insertChild(child, localZOrder);
//set tag or name
if (setTag)
child->setTag(tag);
else
child->setName(name);
child->setParent(this);
child->setOrderOfArrival(s_globalOrderOfArrival++);
#if CC_USE_PHYSICS
// Recursive add children with which have physics body.
auto scene = this->getScene();
if (scene && scene->getPhysicsWorld())
{
//不懂啦，反正和物理引擎相关
child->updatePhysicsBodyTransform(scene);
scene->addChildToPhysicsWorld(child);
}
#endif
if( _running )
{
//生命周期相关的回调
child->onEnter();
// prevent onEnterTransitionDidFinish to be called twice when a node is added in onEnter
if (_isTransitionFinished) {
child->onEnterTransitionDidFinish();
}
}
if (_cascadeColorEnabled)
{
updateCascadeColor();
}
if (_cascadeOpacityEnabled)
{
updateCascadeOpacity();
}
}
// helper used by reorderChild & add
void Node::insertChild(Node* child, int z)
{
_transformUpdated = true;
_reorderChildDirty = true;
//加入vcetor并设置zorder
_children.pushBack(child);
child->_localZOrder = z;
}
4.remove child
/* "remove" logic MUST only be on this method
* If a class want's to extend the 'removeChild' behavior it only needs
* to override this method
*/
void Node::removeChild(Node* child, bool cleanup /* = true */)
{
// explicit nil handling
if (_children.empty())
{
return;
}
ssize_t index = _children.getIndex(child);
if( index != CC_INVALID_INDEX )
this->detachChild( child, index, cleanup );
}
void Node::detachChild(Node *child, ssize_t childIndex, bool doCleanup)
{
// IMPORTANT:
// -1st do onExit
// -2nd cleanup
if (_running)
{
//跟add child时的onEnter onEnterTransitionDidFinish 遥相呼应
child->onExitTransitionDidStart();
child->onExit();
}
#if CC_USE_PHYSICS
child->removeFromPhysicsWorld();
#endif
// If you don't do cleanup, the child's actions will not get removed and the
// its scheduledSelectors_ dict will not get released!
if (doCleanup)
{
//清场，停止动作和timer调度
child->cleanup();
}
// set parent nil at the end
child->setParent(nullptr);
//erase
_children.erase(childIndex);
}
5.
// MARK: draw / visit
void Node::draw()
{
auto renderer = Director::getInstance()->getRenderer();
draw(renderer, _modelViewTransform, true);
}
void Node::draw(Renderer* renderer, const Mat4 &transform, uint32_t flags)
{
//为什么node头文件说node仅是个'void'对象，这就是原因，draw是空实现
}
void Node::visit()
{
auto renderer = Director::getInstance()->getRenderer();
Mat4 parentTransform = Director::getInstance()->getMatrix(MATRIX_STACK_TYPE::MATRIX_STACK_MODELVIEW);
visit(renderer, parentTransform, true);
}
void Node::visit(Renderer* renderer, const Mat4 &parentTransform, uint32_t parentFlags)
{
// quick return if not visible. children won't be drawn.
if (!_visible)
{
return;
}
uint32_t flags = processParentFlags(parentTransform, parentFlags);
// IMPORTANT:
// To ease the migration to v3.0, we still support the Mat4 stack,
// but it is deprecated and your code should not rely on it
Director* director = Director::getInstance();
director->pushMatrix(MATRIX_STACK_TYPE::MATRIX_STACK_MODELVIEW);
director->loadMatrix(MATRIX_STACK_TYPE::MATRIX_STACK_MODELVIEW, _modelViewTransform);
bool visibleByCamera = isVisitableByVisitingCamera();
int i = 0;
if(!_children.empty())
{
//根据zorder排序，若zorder相同则按插入的先后顺序排
sortAllChildren();
//zorder<0就draw，否则break。也就是仅仅draw zorder小于0的node了
// draw children zOrder < 0
for( ; i < _children.size(); i++ )
{
auto node = _children.at(i);
if ( node && node->_localZOrder < 0 )
node->visit(renderer, _modelViewTransform, flags);
else
break;
}
//draw自己
// self draw
if (visibleByCamera)
this->draw(renderer, _modelViewTransform, flags);
//draw zorder>=0的了
//难道这就是官方文档http://cn.cocos2d-x.org/tutorial/show?id=1926
//_in-order walk_算法
for(auto it=_children.cbegin()+i; it != _children.cend(); ++it)
(*it)->visit(renderer, _modelViewTransform, flags);
}
else if (visibleByCamera)
{
this->draw(renderer, _modelViewTransform, flags);
}
director->popMatrix(MATRIX_STACK_TYPE::MATRIX_STACK_MODELVIEW);
// FIX ME: Why need to set _orderOfArrival to 0??
// Please refer to https://github.com/cocos2d/cocos2d-x/pull/6920
// reset for next frame
// _orderOfArrival = 0;
}
6. run action
Action * Node::runAction(Action* action)
{
CCASSERT( action != nullptr, "Argument must be non-nil");
//在后续的action的介绍中将重点介绍
//actionmanager会将action和node关联并驱动action
_actionManager->addAction(action, this, !_running);
return action;
}
7. 对_scheduler的包装
//略，见后面关于调度器的介绍
8. 其他关于物理引擎，opengl，坐标转化和属性的setter getter就先略了
- node节点主要是做为基类存在，定义各种属性
- node中可以继续添加子节点，最终形成树形结构，提供了_in-order walk_算法实现绘制顺序，但他自己的draw方法是空实现
- 包装了timer调度器的一些方法便于使用
- 提供了runAction等方法用于执行action
- 提供了坐标转化，物理引擎相关的辅助方法
Just build something.