如何将QString转换为char *或者相反

先看看官方是如何说的：

How can I convert a QString to char* and vice versa ?(trolltech)

Answer:
In order to convert a QString to a char*, then you first need to get a latin1 representation of the string by calling toLatin1() on it which will return a QByteArray. Then call data() on the QByteArray to get a pointer to the data stored in the byte array. See the documentation:

See the following example for a demonstration:

int main(int argc, char **argv)
{
 QApplication app(argc, argv);
 QString str1 = “Test”;
 QByteArray ba = str1.toLatin1();
 const char *c_str2 = ba.data();
 printf(“str2: %s”, c_str2);
 return app.exec();   
}
Note that it is necessary to store the bytearray before you call data() on it, a call like the following
const char *c_str2 = str2.toLatin1().data();

will make the application crash as the QByteArray has not been stored and hence no longer exists.
To convert a char* to a QString you can use the QString constructor that takes a QLatin1String, e.g:

QString string = QString(QLatin1String(c_str2)) ;

还有其他多种方法：

方法一 —————————————–
#define G2U(s) ( QTextCodec::codecForName(“GBK”)->toUnicode(s) )
#define U2G(s) ( QTextCodec::codecForName(“GBK”)->fromUnicode(s) )

QString str;
QCString cstr;

str = G2U(“中文输入”);
cstr = U2G(str);

QCString有这样一个重载运算符
operator const char * () const

可以这样
printf(“%s\n”, (const char*) cstr);
或是copy出来
char buf[1024];
strcpy(buf, (const char*) cstr);

方法二 —————————————–
如果是中文系统

直接用   (const char*) str.local8Bit()
例如
printf(“%s”, (const char*) str.local8Bit());

str是一个QString

方法三 —————————————–
char str[64];
QTextCodec *textcod = QTextCodec::codecForName(“GBK”);
        QCString string1 = textcod ->fromUnicode(listbox1->currentText());
        strcpy(str,string1);

QString和Std::string

 从char*到 QString可以从fromLocal8Bit()转化
std::string有c_str()的函数使再转化为char*

QString有toAscii()记不清了
你可以看看. 
又是我的粗心酿成大错，我重新查看了一下Qt文档，原来Qt可以直接从std::wstring产生一个QString，用QString::fromStdWString(const std::wstring &)这个静态成员函数即可。我试了试用std::string的c_str()返回的char *构造的QString不能再保存原先的中文信息，而用std::wstring构造的QString则可以用qDebug()输出原先的中文信息 
GB编码与UTF8编码的转换
在主函数app后加上这句：

QUOTE:

QTextCodec::setCodecForLocale(QTextCodec::codecForName(“GB18030″));

然后是从UTF8编码到GB编码的字符串转换方法：

QUOTE:
QString Utf8_To_GB(QString strText)
{
    return QString::fromUtf8(strText.toLocal8Bit().data());
}

至于从GB到UTF8，那大家就经常用了：

QUOTE:

QString GB_To_Utf8(char *strText)
{
    return QString::fromLocal8Bit(strText);
}