TiXmlHandle的使用-简化tinyxml的代码

借鉴于：http://www.cppblog.com/elva/archive/2008/04/24/47907.html

例如：

 <?xml version="1.0" standalone=no>
 <!– Our to do list data –>
 <ToDo>
 <Item priority="1"> Go to the <bold>Toy store!</bold></Item>
 <Item priority="2"> Do bills</Item>
 </ToDo> 

想要健壮地读取一个XML文档，检查方法调用后的返回值是否为null是很重要的。一种安全的检错实现可能会产生像这样的代码：

 TiXmlElement* root = document.FirstChildElement( "Document" );
 if ( root )
 {
 TiXmlElement* element = root->FirstChildElement( "Element" );
 if ( element )
 {
 TiXmlElement* child = element->FirstChildElement( "Child" );
 if ( child )
 {
 TiXmlElement* child2 = child->NextSiblingElement( "Child" );
 if ( child2 )
 {
 // Finally do something useful. 

用句柄（TiXmlHandle）的话就不会这么冗长了，使用TiXmlHandle类，前面的代码就会变成这样：

 TiXmlHandle docHandle( &document );
 TiXmlElement* child2 = docHandle.FirstChild( "Document" ).FirstChild( "Element" ).Child( "Child",  ).ToElement();
 if ( child2 )
 {
 // do something useful 

一、读取XML,设置节点文本

如下XML片段:

 <?xml version="1.0" encoding="UTF-8" standalone="yes" ?>
 <ZXML>
     <ZAPP>
          <VBS_RUNTIME_PARAMS>
                <BROADCAST_VERSION info="版本">8</BROADCAST_VERSION>
                <Broadcast>
                 <FileCount info="资源文件个数">69</FileCount>
                 <SOURCE_1>
                     <ID info="图片编号">1</ID>
                     <Version info="图片版本">1</Version>
                     <Path info="图片路径">/mnt/share/1.bmp</Path>
                     <FileMode info="文件处理模式">0</FileMode>
                 </SOURCE_1>
                 <SOURCE_2>
                     <Path info="图片路径">/mnt/share/2.bmp</Path>
                     <ID info="图片编号">2</ID>
                     <Version info="图片版本">1</Version>
                     <FileMode info="文件处理模式">0</FileMode>
                 </SOURCE_2>
                 .
                 </Broadcast>
          </VBS_RUNTIME_PARAMS>
     </ZAPP>
 </ZXML>

要设置BROADCAST_VERSION节点的值 8为其他值,可参考如下代码(将值加1):
用ReplaceChild( TiXmlNode* replaceThis, const TiXmlNode& withThis )方法替换

 TiXmlDocument doc("zapp.conf");
     doc.LoadFile();
     TiXmlHandle docHandle( &doc );
 TiXmlElement* Broadcast_ver = docHandle.FirstChild("ZXML").FirstChild("ZAPP").FirstChild("VBS_RUNTIME_PARAMS").FirstChildElement("BROADCAST_VERSION").ToElement();
     TiXmlNode * oldnode =  Broadcast_ver->FirstChild();
     const char *ver = Broadcast_ver->GetText();
     int oldVer = atoi(ver);
     CString newVer;
     newVer.Format("%d",oldVer+);
     TiXmlText newText(newVer);
     Broadcast_ver->ReplaceChild(oldnode,newText);
     AfxMessageBox(Broadcast_ver->GetText());//输出值
     doc.SaveFile();

二,删除节点,属性值

RemoveChild( TiXmlNode* removeThis )方法删除父节点的子节点,
RemoveAttribute( const char * name )方法删除属性值.

例如删除BROADCAST_VERSION节点

 TiXmlHandle docHandle( &doc );
     TiXmlElement* Broadcast_ver = docHandle.FirstChild("ZXML").FirstChild("ZAPP").FirstChild("VBS_RUNTIME_PARAMS").ToElement();

     TiXmlNode * node =  Broadcast_ver->FirstChild("BROADCAST_VERSION");

     Broadcast_ver->RemoveChild(node);

也可以删除整个SOURCE_1节点:

 TiXmlHandle docHandle( &doc );
     TiXmlElement* Broadcast = docHandle.FirstChild("ZXML").FirstChild("ZAPP").FirstChild("VBS_RUNTIME_PARAMS").FirstChild("Broadcast").ToElement();

     TiXmlNode * node =  Broadcast->FirstChild("SOURCE_1");

     Broadcast->RemoveChild(node);

删除BROADCAST_VERSION的info属性:

 TiXmlHandle docHandle( &doc );
     TiXmlElement* Broadcast_ver = docHandle.FirstChild("ZXML").FirstChild("ZAPP").FirstChild("VBS_RUNTIME_PARAMS").FirstChildElement("BROADCAST_VERSION").ToElement();

     Broadcast_ver->RemoveAttribute("info"); //删除info

可以借助NextSiblingElement()方法实现递归删除.

三,添加节点,属性值

例如在SOURCE_3下添加BROADCAST_PID节点:

 TiXmlHandle docHandle( &doc );
     TiXmlElement* Broadcast = docHandle.FirstChild("ZXML").FirstChild("ZAPP").FirstChild("VBS_RUNTIME_PARAMS").FirstChild("Broadcast").ToElement();
     TiXmlElement* Broadcast_Pid = new TiXmlElement("BROADCAST_PID");
     TiXmlText *text =new TiXmlText("");
     Broadcast_Pid->SetAttribute("info","the pid");
     Broadcast_Pid->LinkEndChild(text);
     Broadcast->LinkEndChild(Broadcast_Pid);

将在SOURCE_3后添加新的节点:

 <BROADCAST_PID info="the pid">7215</BROADCAST_PID>

四,最后说一下中文乱码的问题

乱码是由于GB2312与UTF8之间转换不当造成的,tinyxml在处理UTF8本身没有问题,当你打开一个UTF8的文档,可以在加载的时候指定UTF8的方式,或者文档声明处指明的编码格式,tinyxml会按照相应的编码格式加载,但很多时候当我们输出或写入中文字段时会出现乱码,无论在内存,还是打印出来的内容.这是因为我们的软件通常是GB2312编码,而读取或写入的内容是UTF8,自然就会出错.可以借助网上的两个函数来实现转换(原作者不详):

 void ConvertUtf8ToGBK(CString& strUtf8)
     {
         int len=MultiByteToWideChar(CP_UTF8, , (LPCTSTR)strUtf8, -, NULL,);
         unsigned short * wszGBK = new unsigned short[len+];
         memset(wszGBK, , len *  + );
         MultiByteToWideChar(CP_UTF8, , (LPCTSTR)strUtf8, -, wszGBK, len);

         len = WideCharToMultiByte(CP_ACP, , wszGBK, -, NULL, , NULL, NULL);
         char *szGBK=new char[len + ];
         memset(szGBK, , len + );
         WideCharToMultiByte (CP_ACP, , wszGBK, -, szGBK, len, NULL,NULL);

         strUtf8 = szGBK;
         delete[] szGBK;
         delete[] wszGBK;
     }

     void ConvertGBKToUtf8(CString& strGBK)
     {
         int len=MultiByteToWideChar(CP_ACP, , (LPCTSTR)strGBK, -, NULL,);
         unsigned short * wszUtf8 = new unsigned short[len+];
         memset(wszUtf8, , len *  + );
         MultiByteToWideChar(CP_ACP, , (LPCTSTR)strGBK, -, wszUtf8, len);

         len = WideCharToMultiByte(CP_UTF8, , wszUtf8, -, NULL, , NULL, NULL);
         char *szUtf8=new char[len + ];
         memset(szUtf8, , len + );
         WideCharToMultiByte (CP_UTF8, , wszUtf8, -, szUtf8, len, NULL,NULL);

         strGBK = szUtf8;
         delete[] szUtf8;
         delete[] wszUtf8;
     }

当然,你也可以用MultiByteToWideChar,WideCharToMultiByte函数自己实现转换.以上是简单应用的几个举例,理解他们,相信你已经能写出满足自己需要的代码了.