QString->string->wstring->LPCWSTR

QFileInfo info("./records.db");
std::string str = info.absoluteFilePath().toStdString(); //将QString转换为string
std::wstring wstr(str.length(), L‘ ‘);　　//初始化宽字节wstr
std::copy(str.begin(), str.end(), wstr.begin());　　//将str复制到wstr
LPCWSTR path = wstr.c_str();　　//将wstr转换为C字符串的指针,然后赋值给path

转换过程：QString->string->wstring->LPCWSTR

http://www.cnblogs.com/luoxiang/p/5456173.html