QString转换成char * 的时候，一定要定义一个QBateArray的变量。不能连写

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)) ;