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", 1 ).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+1);
    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("7215");
    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, 0, (LPCTSTR)strUtf8, -1, NULL,0);
        unsigned short * wszGBK = new unsigned short[len+1];
        memset(wszGBK, 0, len * 2 + 2);
        MultiByteToWideChar(CP_UTF8, 0, (LPCTSTR)strUtf8, -1, wszGBK, len);

        len = WideCharToMultiByte(CP_ACP, 0, wszGBK, -1, NULL, 0, NULL, NULL);
        char *szGBK=new char[len + 1];
        memset(szGBK, 0, len + 1);
        WideCharToMultiByte (CP_ACP, 0, wszGBK, -1, szGBK, len, NULL,NULL);

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


    void ConvertGBKToUtf8(CString& strGBK)
    {
        int len=MultiByteToWideChar(CP_ACP, 0, (LPCTSTR)strGBK, -1, NULL,0);
        unsigned short * wszUtf8 = new unsigned short[len+1];
        memset(wszUtf8, 0, len * 2 + 2);
        MultiByteToWideChar(CP_ACP, 0, (LPCTSTR)strGBK, -1, wszUtf8, len);

        len = WideCharToMultiByte(CP_UTF8, 0, wszUtf8, -1, NULL, 0, NULL, NULL);
        char *szUtf8=new char[len + 1];
        memset(szUtf8, 0, len + 1);
        WideCharToMultiByte (CP_UTF8, 0, wszUtf8, -1, 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.