c++编程中，类的声明文件和实现文件为什么都要包含标准库？

在类的定义文件中写了头文件，如#include .在类的实现中为什么还要包含#include 这个头文件呢？

你可以试一下，实现文件不含 #include 。
iostream -- 输入输出流。
通常 因为是分开的2个文件，分开编译时，如果 里面 遇到 与输入输出 有关 函数 时， 需要 函数原型， 这时需要 头文件。 一般 标准头文件 有 宏保护 指令， 重复包含了， 它会 只包含一次，忽略 多余的 #include。
所以 ， 写多了 不要紧， 写少了 不行。

安装psdk就可以用了，之前有写过一个类在mfc里面调用，并能成功与蓝牙手机通信，只不过是非标准的蓝牙协议。代码如下： =====================h头文件======================== #ifndef ns_bth #include "ws2bth.h" //如果没有定义ns_bth宏，则将psdk头文件包含进来 #endif #ifndef bth_addr typedef ulonglong bth_addr; #endif #ifndef safe_delete #define safe_delete(pobj) {if(pobj) delete pobj; pobj = null;} #endif #ifndef safe_deleterg #define safe_deleterg(pobj) {if(pobj) delete [] pobj; pobj = null;} #endif #define receive_over_command 0x00001000 typedef struct _tag_bthdev_info { bth_addr btaddr; tchar szaddr[32]; tchar szname[128]; _tag_bthdev_info() { memset(this, 0, sizeof(this)); } } bthdev_info; class cggbluetooth { public: cggbluetooth(); ~cggbluetooth(); bool startsearchbthdev(in dword dwcontrolflags); bool getnextbthdev( in out bthdev_info *pcbthdevinfo, in dword dwcontrolflags = lup_return_name | lup_return_addr | lup_flushcache ); bool endsearchbthdev(); //socket api bool create(int af = af_bth, int type = sock_stream, int protocol = bthproto_rfcomm); bool close(); //if no error occurs, this function returns zero. if an error occurs, it returns socket_error int bind(bth_addr sktaddr = 0, ulong port = bt_port_any); int listen(in int backlog); int getsockname(bth_addr *psktaddr, ulong *port); int setbthservice(tchar *lpservicename); int accept(cggbluetooth *pcbth); int connect(bth_addr sktaddr, ulong port, int nmsecond = -1); int send(lpvoid lpdata, int len, int flags = 0); int recv(lpvoid lpdata, int len, int flags = 0); int sendall(lpvoid lpdata, int len, int flags = 0); int recvall(lpvoid lpdata, int len, int flags = 0); private: void hexmac2string(bth_addr dw64addr, tchar *pstrmac); private: handle m_hlookup; socket m_hsocket; sockaddr_bth m_sktaddr; }; ==============cpp文件================ #include "stdafx.h" #include "ggbluetooth.h" //#include "tchar.h" cggbluetooth::cggbluetooth() : m_hlookup(null) , m_hsocket(null) { memset(&m_sktaddr, 0, sizeof(m_sktaddr)); } cggbluetooth::~cggbluetooth() { endsearchbthdev(); close(); } void cggbluetooth::hexmac2string(bth_addr dw64addr, tchar *pstrmac) { byte *pbaddr = (byte*)&dw64addr; _stprintf( pstrmac, _t("%02x:%02x:%02x:%02x:%02x:%02x"), pbaddr[5], pbaddr[4], pbaddr[3], pbaddr[2], pbaddr[1], pbaddr[0] ); } bool cggbluetooth::startsearchbthdev(in dword dwcontrolflags) { wsaqueryset wsaq; zeromemory(&wsaq, sizeof(wsaq)); wsaq.dwsize = sizeof(wsaq); wsaq.dwnamespace = ns_bth; wsaq.lpcsabuffer = null; return wsalookupservicebegin(&wsaq, dwcontrolflags, &m_hlookup) == error_success ? true : false; } bool cggbluetooth::getnextbthdev( in out bthdev_info *pcbthdevinfo, in dword dwcontrolflags ) { if (!m_hlookup || !pcbthdevinfo) { return false; } memset(pcbthdevinfo->szaddr, 0, sizeof(pcbthdevinfo->szaddr)); memset(pcbthdevinfo->szname, 0, sizeof(pcbthdevinfo->szname)); union { char buf[5000]; double __unused; // ensure proper alignment }; lpwsaqueryset pwsaresults = (lpwsaqueryset)buf; dword dwsize = sizeof(buf); int nresult; zeromemory(pwsaresults, sizeof(wsaqueryset)); pwsaresults->dwsize = sizeof(wsaqueryset); pwsaresults->dwnamespace = ns_bth; pwsaresults->lpblob = null; nresult = wsalookupservicenext (m_hlookup, dwcontrolflags, &dwsize, pwsaresults); if (nresult == error_success) { pcbthdevinfo->btaddr = ((sockaddr_bth *)pwsaresults->lpcsabuffer->remoteaddr.lpsockaddr)->btaddr; bool bhavename = pwsaresults->lpszserviceinstancename && *(pwsaresults->lpszserviceinstancename); if (bhavename) { hexmac2string(pcbthdevinfo->btaddr, pcbthdevinfo->szaddr); _tcscpy(pcbthdevinfo->szname, pwsaresults->lpszserviceinstancename); } return true; } return false; } bool cggbluetooth::endsearchbthdev() { if (m_hlookup) { wsalookupserviceend(m_hlookup); m_hlookup = null; return true; } return false; } ///=============================== bool cggbluetooth::create(int af, int type, int protocol) { if (m_hsocket) { return false; } m_hsocket = socket(af, type, protocol); m_sktaddr.addressfamily = af; m_sktaddr.serviceclassid = guid_null; return m_hsocket == invalid_socket ? false : true; } bool cggbluetooth::close() { if (m_hsocket) { closesocket(m_hsocket); return true; } return false; } int cggbluetooth::bind(bth_addr sktaddr, ulong port) { m_sktaddr.btaddr = sktaddr; m_sktaddr.port = port; return bind(m_hsocket, (sockaddr *)&m_sktaddr, sizeof(m_sktaddr)); } int cggbluetooth::listen(int backlog) { return listen(m_hsocket, backlog); } int cggbluetooth::getsockname(bth_addr *psktaddr, ulong *port) { int nlen = sizeof(m_sktaddr); int nresult = getsockname(m_hsocket, (sockaddr *)&m_sktaddr, &nlen); if (nresult == 0) { *psktaddr = m_sktaddr.btaddr; *port = m_sktaddr.port; } return nresult; } guid obexfiletransferserviceclass_uuid_ex = {0x00001106, 0x0000, 0x1000, 0x80, 0x00, 0x00, 0x80, 0x5f, 0x9b, 0x34, 0xfb}; int cggbluetooth::setbthservice(tchar * lpservicename) { csaddr_info sockinfo; sockinfo.iprotocol = bthproto_rfcomm; sockinfo.isockettype = sock_stream; sockinfo.localaddr.lpsockaddr = (sockaddr *)&m_sktaddr; sockinfo.localaddr.isockaddrlength = sizeof(m_sktaddr); sockinfo.remoteaddr.lpsockaddr = (sockaddr *)&m_sktaddr; sockinfo.remoteaddr.isockaddrlength = sizeof(m_sktaddr); wsaqueryset svcinfo = {0}; svcinfo.dwsize = sizeof(svcinfo); svcinfo.dwnamespace = ns_bth; svcinfo.lpszserviceinstancename = lpservicename; svcinfo.lpserviceclassid = &obexfiletransferserviceclass_uuid_ex; svcinfo.dwnumberofcsaddrs = 1; svcinfo.lpcsabuffer = &sockinfo; return wsasetservice(&svcinfo, rnrservice_register, 0); } int cggbluetooth::accept(cggbluetooth *pcbth) { sockaddr_bth ca; int size = sizeof(ca); pcbth->m_hsocket = accept (m_hsocket, (sockaddr *)&ca, &size); pcbth->m_sktaddr = ca; return pcbth->m_hsocket == invalid_socket ? socket_error : 0; } int cggbluetooth::connect(bth_addr sktaddr, ulong port, int nmsecond) { sockaddr_bth sa = {0}; sa.addressfamily = af_bth; sa.btaddr = sktaddr; sa.port = port; if (nmsecond == -1) { return connect(m_hsocket, (lpsockaddr)&sa, sizeof(sockaddr_bth)); } ulong non_blocking = 1; ulong blocking = 0; int nresult = ioctlsocket(m_hsocket, fionbio, &non_blocking); if (nresult == socket_error) { return nresult; } nresult = socket_error; if (connect(m_hsocket, (lpsockaddr)&sa, sizeof(sockaddr_bth)) == socket_error) { struct timeval tv; fd_set writefds; // 设置连接超时时间 tv.tv_sec = nmsecond / 1000; // 秒数 tv.tv_usec = nmsecond % 1000; // 毫秒 fd_zero(&writefds); fd_set(m_hsocket, &writefds); nresult = select((int)m_hsocket + 1, null, &writefds, null, &tv); if(nresult > 0) { if(fd_isset(m_hsocket, &writefds)) { int error = 0; int len = sizeof(error); //下面的一句一定要，主要针对防火墙 if(!(getsockopt(m_hsocket, sol_socket, so_error, (char *)&error, &len) != 0 || error != 0)) { nresult = 0; } } } else if (nresult == 0) { nresult = -2; } } if (ioctlsocket(m_hsocket, fionbio, &blocking) == socket_error) { nresult = socket_error; } return nresult; } int cggbluetooth::send(lpvoid lpdata, int len, int flags) { return send(m_hsocket, (char *)lpdata, len, flags); } int cggbluetooth::recv(lpvoid lpdata, int len, int flags) { return recv(m_hsocket, (char *)lpdata, len, flags); } int cggbluetooth::sendall(lpvoid lpdata, int len, int flags) { int ncount = send(m_hsocket, (char *)lpdata, len, flags); if (ncount == socket_error && wsagetlasterror() != wsaewouldblock) { return socket_error; } int ncommand = 0; ncount = recv(m_hsocket, (char *)&ncommand, 4, flags); if (ncount != 4 || ncommand != receive_over_command) { return socket_error; } return error_success; } int cggbluetooth::recvall(lpvoid lpdata, int len, int flags) { int ncount = -1, ncurrecv = 0, nmaxread = 32 * 1024; while (ncurrecv < len) { if (len - ncurrecv < nmaxread) { nmaxread = len - ncurrecv; } ncount = recv(m_hsocket, (char *)lpdata + ncurrecv, nmaxread, flags); if (ncount == socket_error) { if (wsagetlasterror() == wsaewouldblock) { sleep(1); continue; } else { return socket_error; } } ncurrecv += ncount; } int ncommand = receive_over_command; ncount = send(m_hsocket, (char *)&ncommand, 4, flags); if (ncount == socket_error && wsagetlasterror() != wsaewouldblock) { return socket_error; } return error_success; }