Cocos2d-x实例：设置背景音乐与音效-设置场景实现

设置场景（Setting），Setting.h文件代码如下：

#ifndef __Setting_SCENE_H__
#define __Setting_SCENE_H__


#include "cocos2d.h"
#include "SimpleAudioEngine.h"


class Setting : public cocos2d::Layer
{
    bool isEffect;                                                      ①
public:
    static cocos2d::Scene* createScene();
    virtual bool init();
    virtual void onEnter();
    virtual void onEnterTransitionDidFinish();
    virtual void onExit();
    virtual void onExitTransitionDidStart();
    virtual void cleanup();

    void menuSoundToggleCallback(cocos2d::Ref* pSender);
    void menuMusicToggleCallback(cocos2d::Ref* pSender);
    void menuOkCallback(cocos2d::Ref* pSender);

    CREATE_FUNC(Setting);
};


#endif // __Setting_SCENE_H__


#define __HELLOWORLD_SCENE_H__

上述代码第①是定义布尔类型成员变量isEffect，它用来保存现在是否允许音效，事实上是否允许音效和背景音乐播放状态应该持久化到文件中，由于我们还没有介绍数据持久化，所以我们采用isEffect变量记录状态，当我们在后面的章节学习完成数据持久化后，再保存它们状态。其它的代码与HelloWorld场景代码非常相似，这里不再赘述。Setting.cpp文件代码如下：

#include "SettingScene.h"


USING_NS_CC;
using namespace CocosDenshion;


… …
bool Setting::init()
{
    if ( !Layer::init() )
    {
        return false;
    }


    log("Setting init");

    Size visibleSize = Director::getInstance()->getVisibleSize();
    Point origin = Director::getInstance()->getVisibleOrigin();


    Sprite *bg = Sprite::create("setting-back.png");

    bg->setPosition(Point(origin.x + visibleSize.width/2,
                             origin.y + visibleSize.height /2));
    this->addChild(bg);


    //音效
    auto soundOnMenuItem = MenuItemImage::create(
                             "on.png",
                             "on.png");
    auto soundOffMenuItem = MenuItemImage::create(
                             "off.png",
                             "off.png");

    auto soundToggleMenuItem = MenuItemToggle::createWithCallback(
                                CC_CALLBACK_1(Setting::menuSoundToggleCallback, this),
                                                soundOffMenuItem,
                                                soundOnMenuItem,
                                                NULL);
    soundToggleMenuItem->setPosition(Director::getInstance()->convertToGL(Point(818, 220)));

    //背景音乐
    auto musicOnMenuItem  = MenuItemImage::create(
                             "on.png",
                             "on.png");
    auto musicOffMenuItem  = MenuItemImage::create(
                             "off.png",
                             "off.png");
    auto musicToggleMenuItem = MenuItemToggle::createWithCallback(
                                CC_CALLBACK_1(Setting::menuMusicToggleCallback, this),
                                                    musicOffMenuItem,
                                                    musicOnMenuItem,
                                                    NULL );
    musicToggleMenuItem->setPosition(Director::getInstance()->convertToGL(Point(818, 362)));


    //Ok按钮
    auto okMenuItem  = MenuItemImage::create(
                             "ok-down.png",
                             "ok-up.png",
                             CC_CALLBACK_1(Setting::menuOkCallback, this));


    okMenuItem->setPosition(Director::getInstance()->convertToGL(Point(600, 510)));


    Menu* mn = Menu::create(soundToggleMenuItem, musicToggleMenuItem,okMenuItem, NULL);
    mn->setPosition(Point::ZERO);
    this->addChild(mn);


    return true;
}


void Setting::menuOkCallback(Ref* pSender)
{
    Director::getInstance()->popScene();
    if (isEffect) {
        SimpleAudioEngine::getInstance()->playEffect("sound/Blip.wav");                  ①
    }
}


void Setting::menuSoundToggleCallback(Ref* pSender)                         ②
{
    auto soundToggleMenuItem = (MenuItemToggle*)pSender;
    log("soundToggleMenuItem %d", soundToggleMenuItem->getSelectedIndex());


    if (isEffect) {
        SimpleAudioEngine::getInstance()->playEffect("sound/Blip.wav");                  ③
    }


    if (soundToggleMenuItem->getSelectedIndex() == 1) {//选中状态Off -> On                ④
        isEffect = false;
    } else {
        isEffect = true;
        SimpleAudioEngine::getInstance()->playEffect("sound/Blip.wav");                  ⑤
    }
}


void Setting::menuMusicToggleCallback(Ref* pSender)                         ⑥
{
    auto musicToggleMenuItem = (MenuItemToggle*)pSender;
    log("musicToggleMenuItem %d", musicToggleMenuItem->getSelectedIndex());

    if (musicToggleMenuItem->getSelectedIndex() == 1) {//选中状态Off -> On                ⑦
        SimpleAudioEngine::getInstance()->stopBackgroundMusic("sound/Synth.mp3");
    } else {
        SimpleAudioEngine::getInstance()->playBackgroundMusic("sound/Synth.mp3");
    }
    if (isEffect) {
        SimpleAudioEngine::getInstance()->playEffect("sound/Blip.wav");                  ⑧
    }
}


void Setting::onEnter()
{
    Layer::onEnter();
    log("Setting onEnter");
}


void Setting::onEnterTransitionDidFinish()
{
    Layer::onEnterTransitionDidFinish();
    log("Setting onEnterTransitionDidFinish");
    isEffect = true;
    //播放
    SimpleAudioEngine::getInstance()->playBackgroundMusic("sound/Synth.mp3", true);      ⑨
}


void Setting::onExit()
{
    Layer::onExit();
    log("Setting onExit");
}


void Setting::onExitTransitionDidStart()
{
    Layer::onExitTransitionDidStart();
    log("Setting onExitTransitionDidStart");
}


void Setting::cleanup()
{
    Layer::cleanup();
    log("Setting cleanup");
    //停止
    SimpleAudioEngine::getInstance()->stopBackgroundMusic("sound/Synth.mp3");            ⑩
}

上述代码第①、③、⑧行是在判断isEffect为true（音效播放开关打开）情况下播放音效。
代码第②行menuSoundToggleCallback是用户点击音效开发按钮时候回调函数，其中第④行代码是判断是否按钮状态从Off -> On，如果是则将开关变量isEffect 设置为false，否则为true，而且通过第⑤行代码SimpleAudioEngine::getInstance()->playEffect("sound/Blip.wav")播放一次音效。
代码第⑥行menuMusicToggleCallback是用户点击背景音乐按钮时候回调函数，其中第⑦行代码是判断是否按钮状态从Off -> On，如果是则停止播放背景音乐，否则为开始播放。

第⑧行代码是onEnterTransitionDidFinish()函数中播放背景音乐。第⑨行代码是cleanup()函数中停止播放背景音乐。

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