Cocos2D-x schedule & scheduleUpdate 的使用

开始学习Cocos2D-x

在cocos2d-x中提供了好几个定时器的方法供调用我们可以在CCNode.h 这个头文件中找到相应的方法，下面整理一下：

（1）使用下面这个方法，那么节点在每一帧都会执行update方法。

/** 
     * Schedules the "update" method. 
     *
     * It will use the order number 0. This method will be called every frame.
     * Scheduled methods with a lower order value will be called before the ones that have a higher order value.
     * Only one "update" method could be scheduled per node.
     */
    void scheduleUpdate(void);

在注释中说到，该方法的order（优先级数）为0，order（优先级数）越小那么越先调度。每一个节点都只能有一个update调度方法。

注意要重写该update方法。

/* 
     * Update method will be called automatically every frame if "scheduleUpdate" is called, and the node is "live"
     */
    virtual void update(float delta);

要取消这个定时器调用也很简单。

/* 
     * Unschedules the "update" method.
     * @see scheduleUpdate();
     */
    void unscheduleUpdate(void);

cocos2d-x中还提供了这样一个方法，这个方法的作用和scheduleUpdate类似，只不过还有指定一个优先级，优先级数越小，那么越先执行。

/** 
     * Schedules the "update" method with a custom priority. 
     *
     * This selector will be called every frame.
     * Scheduled methods with a lower priority will be called before the ones that have a higher value.
     * Only one "update" selector could be scheduled per node (You can't have 2 'update' selectors).
     */
    void scheduleUpdateWithPriority(int priority);

（2）cocos2d-x中还提供了好几个schedule方法。这些方法的调用都可以指定节点执行特定的selector。

①

/**
     * Schedules a custom selector.
     *
     * If the selector is already scheduled, then the interval parameter will be updated without scheduling it again.
     * @code
     * // firstly, implement a schedule function
     * void MyNode::TickMe(float dt);
     * // wrap this function into a selector via schedule_selector marco.
     * this->schedule(schedule_selector(MyNode::TickMe), 0, 0, 0);
     * @endcode
     *
     * @param interval  Tick interval in seconds. 0 means tick every frame. If interval = 0, it's recommended to use scheduleUpdate() instead.
     * @param repeat    The selector will be excuted (repeat + 1) times, you can use kCCRepeatForever for tick infinitely.
     * @param delay     The amount of time that the first tick will wait before execution.
     */
    void schedule(SEL_SCHEDULE selector, float interval, unsigned int repeat, float delay);

参数中指定了selector，执行时间间隔，重复执行次数（可以使用kCCRepeatForever表示无限循环） ，开始执行前的延时。

②

/**
     * Schedules a custom selector with an interval time in seconds.
     * @see schedule(SEL_SCHEDULE, float, unsigned int, float)
     *
     * @param selector      A function wrapped as a selector
     * @param interval      Callback interval time in seconds. 0 means tick every frame,
     */
    void schedule(SEL_SCHEDULE selector, float interval);

参数中指定了selector和执行时间间隔。

③

/**
     * Schedules a selector that runs only once, with a delay of 0 or larger
     * @see schedule(SEL_SCHEDULE, float, unsigned int, float)
     *
     * @param selector      A function wrapped as a selector
     * @param delay         The amount of time that the first tick will wait before execution.
     */
    void scheduleOnce(SEL_SCHEDULE selector, float delay);

参数中指定了selector和开始执行前的延时。

④

 /**
     * Schedules a custom selector, the scheduled selector will be ticked every frame
     * @see schedule(SEL_SCHEDULE, float, unsigned int, float)
     *
     * @param selector      A function wrapped as a selector
     */
    void schedule(SEL_SCHEDULE selector);

这个方法中的参数只指定了selector，那么它的作用其实就等同于scheduleUpdate，即节点在每一帧都会执行selector方法。

⑤ 取消定时器schedule的方法

/** 
     * Unschedules a custom selector.
     * @see schedule(SEL_SCHEDULE, float, unsigned int, float)
     *
     * @param selector      A function wrapped as a selector
     */
    void unschedule(SEL_SCHEDULE selector);

取消所有的定时器方法。

/** 
     * Unschedule all scheduled selectors: custom selectors, and the 'update' selector.
     * Actions are not affected by this method.
     */
    void unscheduleAllSelectors(void);

⑥ 下面的两个方法是用于恢复和暂停定时器方法的。他们一般都是在onEnter和onExit方法种调用的。

/** 
     * Resumes all scheduled selectors and actions.
     * This method is called internally by onEnter
     */
    void resumeSchedulerAndActions(void);
    /** 
     * Pauses all scheduled selectors and actions.
     * This method is called internally by onExit
     */
    void pauseSchedulerAndActions(void);