Cocos2d-x源代码解析（1）——地图模块（1）

cocos通过加载tiled 生成的tmx文件来生成游戏地图。本文主要分析cocos加载地图模块的源代码。

 

如图所看到的，地图加载模块由以上几个类组成。

对外的入口是类CCTMXTiledMap，在使用该类时。程序猿不须要知道其底层的其它类便可解析tmx文件生成地图。

那么。我们首先分析类CCTMXTiledMap是怎样调用其它类进行解析，该类的声明例如以下：

class CC_DLL CCTMXTiledMap :public CCNode
{
    /** the map's size property measured intiles */
    CC_SYNTHESIZE_PASS_BY_REF(CCSize,m_tMapSize, MapSize);
    /** the tiles's size property measured inpixels */
    CC_SYNTHESIZE_PASS_BY_REF(CCSize,m_tTileSize, TileSize);
    /** map orientation */
    CC_SYNTHESIZE(int, m_nMapOrientation,MapOrientation);
    /** object groups */
    CC_PROPERTY(CCArray*, m_pObjectGroups,ObjectGroups);
    /** properties */
    CC_PROPERTY(CCDictionary*, m_pProperties,Properties);
public:
    /**
     * @js ctor
     */
    CCTMXTiledMap();
    /**
     * @js NA
     * @lua NA
     */
    virtual ~CCTMXTiledMap();

    /** creates a TMX Tiled Map with a TMXfile.*/
    static CCTMXTiledMap* create(const char*tmxFile);

    /** initializes a TMX Tiled Map with a TMXformatted XML string and a path to TMX resources */
    static CCTMXTiledMap* createWithXML(constchar* tmxString, const char* resourcePath);

    /** initializes a TMX Tiled Map with a TMXfile */
    bool initWithTMXFile(const char *tmxFile);

    /** initializes a TMX Tiled Map with a TMXformatted XML string and a path to TMX resources */
    bool initWithXML(const char* tmxString,const char* resourcePath);

    /** return the TMXLayer for the specificlayer
     * @js getLayer
     */
    CCTMXLayer* layerNamed(const char*layerName);

    /** return the TMXObjectGroup for thespecific group
     * @js getObjectGroup
     */
    CCTMXObjectGroup* objectGroupNamed(constchar *groupName);

    /** return the value for the specificproperty name
     * @js getProperty
     */
    CCString *propertyNamed(const char*propertyName);

    /** return properties dictionary for tileGID */
    CCDictionary* propertiesForGID(int GID);

private:
   CCTMXLayer *parseLayer(CCTMXLayerInfo *layerInfo, CCTMXMapInfo *mapInfo);
    CCTMXTilesetInfo *tilesetForLayer(CCTMXLayerInfo *layerInfo, CCTMXMapInfo *mapInfo);
    void buildWithMapInfo(CCTMXMapInfo*mapInfo);
protected:
    //! tile properties
    CCDictionary* m_pTileProperties;

};

通过查看函数实现，我们发现函数

/** creates a TMX Tiled Map with a TMX file.*/
    static CCTMXTiledMap* create(const char*tmxFile);

通过调用函数

/** initializes a TMX Tiled Mapwith a TMX file */
    bool initWithTMXFile(const char *tmxFile);

来实现文件的解析。并创建一个CCTMXTiledMap对象返回给使用者。

boolCCTMXTiledMap::initWithTMXFile(const char *tmxFile)
{
    CCAssert(tmxFile != NULL &&strlen(tmxFile)>0, "TMXTiledMap: tmx file should not bi NULL");

    setContentSize(CCSizeZero);

    CCTMXMapInfo *mapInfo =CCTMXMapInfo::formatWithTMXFile(tmxFile);

    if (! mapInfo)
    {
        return false;
    }
    CCAssert(mapInfo->getTilesets()->count() != 0, "TMXTiledMap: Map not found.Please check the filename.");
    buildWithMapInfo(mapInfo);

    return true;
}

通过看源代码。我们发现有2个重要的函数 CCTMXMapInfo::formatWithTMXFile(tmxFile)和buildWithMapInfo(mapInfo)，看名字应该能知道formatWithTMXFile是解析XML文件将其结构化。buildWithMapInfo是将结构化的数据变成CCNode从而显示在游戏界面上。

接下来，我们查看CCTMXMapInfo是怎样组织数据以及怎样解析XML文件的，首先我们还是查看CCTMXMapInfo的声明

class CC_DLL CCTMXMapInfo :public CCObject, public CCSAXDelegator
{
public:
    /// map orientation
    CC_SYNTHESIZE(int,    m_nOrientation, Orientation);
    /// map width & height
    CC_SYNTHESIZE_PASS_BY_REF(CCSize,m_tMapSize, MapSize);
    /// tiles width & height
    CC_SYNTHESIZE_PASS_BY_REF(CCSize,m_tTileSize, TileSize);
    /// Layers
    CC_PROPERTY(CCArray*, m_pLayers, Layers);
    /// tilesets
    CC_PROPERTY(CCArray*, m_pTilesets,Tilesets);
    /// ObjectGroups
    CC_PROPERTY(CCArray*, m_pObjectGroups,ObjectGroups);
    /// parent element
    CC_SYNTHESIZE(int, m_nParentElement,ParentElement);
    /// parent GID
    CC_SYNTHESIZE(unsigned int, m_uParentGID,ParentGID);
    /// layer attribs
    CC_SYNTHESIZE(int, m_nLayerAttribs,LayerAttribs);
    /// is storing characters?
    CC_SYNTHESIZE(bool, m_bStoringCharacters,StoringCharacters);
    /// properties
    CC_PROPERTY(CCDictionary*, m_pProperties,Properties);
public:
    /**
     * @js ctor
     * @lua NA
     */
    CCTMXMapInfo();
    /**
     * @js NA
     * @lua NA
     */
    virtual ~CCTMXMapInfo();
    /** creates a TMX Format with a tmx file */
    static CCTMXMapInfo *formatWithTMXFile(const char *tmxFile);
    /** creates a TMX Format with an XML stringand a TMX resource path */
    static CCTMXMapInfo * formatWithXML(constchar* tmxString, const char* resourcePath);
    /** initializes a TMX format with a  tmx file
     * @lua NA
     */
    bool initWithTMXFile(const char *tmxFile);
    /** initializes a TMX format with an XMLstring and a TMX resource path
     * @lua NA
     */
    bool initWithXML(const char* tmxString,const char* resourcePath);
    /** initializes parsing of an XML file,either a tmx (Map) file or tsx (Tileset) file */
    bool parseXMLFile(const char *xmlFilename);
    /* initializes parsing of an XML string,either a tmx (Map) string or tsx (Tileset) string */
    bool parseXMLString(const char *xmlString);

    CCDictionary* getTileProperties();
    void setTileProperties(CCDictionary*tileProperties);

    /** implement pure virtual methods ofCCSAXDelegator
     * @js NA
     */
    void startElement(void *ctx, const char*name, const char **atts);
    /**
     * @js NA
     */
    void endElement(void *ctx, const char*name);
    /**
     * @js NA
     */
    void textHandler(void *ctx, const char *ch,int len);

    inline const char* getCurrentString(){return m_sCurrentString.c_str(); }
    inline void setCurrentString(const char*currentString){ m_sCurrentString = currentString; }
    inline const char* getTMXFileName(){ returnm_sTMXFileName.c_str(); }
    inline void setTMXFileName(const char*fileName){ m_sTMXFileName = fileName; }
private:
    void internalInit(const char* tmxFileName,const char* resourcePath);
protected:
    //! tmx filename
    std::string m_sTMXFileName;
    // tmx resource path
    std::string m_sResources;
    //! current string
    std::string m_sCurrentString;
    //! tile properties
    CCDictionary* m_pTileProperties;
    unsigned int m_uCurrentFirstGID;
};

通过查看声明 我们发现CCTMXMapInfo主要包含下面几个数据：

1. TMXLayerInfo的数组，用来存放地图信息
2. TMXTilesetInfo的数组，用来存放块信息
3. ObjectGroups的数组

另外。CCTMXMapInfo中有几个重要的函数：

 bool initWithXML(const char* tmxString, constchar* resourcePath);
    /** initializes parsing of an XML file,either a tmx (Map) file or tsx (Tileset) file */
    bool parseXMLFile(const char *xmlFilename);
    /* initializes parsing of an XML string, eithera tmx (Map) string or tsx (Tileset) string */
    bool parseXMLString(const char *xmlString);

这3个函数是libxml2中所须要解析xml的代理函数，分别表示标签的開始，标签的结束，标签的内容

解析xml的标签就在这几个函数中。