G:\qt files\myFtp-build-desktop/../myFtp/widget.cpp:11: undefined reference to `_imp___ZN4QFtp13connectToHostERK7QStringt'
G:\qt files\myFtp-build-desktop/../myFtp/widget.cpp:12: undefined reference to `_imp___ZN4QFtp5loginERK7QStringS2_'
G:\qt files\myFtp-build-desktop/../myFtp/widget.cpp:13: undefined reference to `_imp___ZN4QFtp2cdERK7QString'
G:\qt files\myFtp-build-desktop/../myFtp/widget.cpp:14: undefined reference to `_imp___ZN4QFtp3getERK7QStringP9QIODeviceNS_12TransferTypeE'
G:\qt files\myFtp-build-desktop/../myFtp/widget.cpp:15: undefined reference to `_imp___ZN4QFtp5closeEv'
G:\qt files\myFtp-build-desktop/../myFtp/widget.cpp:10: undefined reference to `_imp___ZN4QFtpC1EP7QObject'
G:\qt files\myFtp-build-desktop/../myFtp/widget.cpp:11: undefined reference to `_imp___ZN4QFtp13connectToHostERK7QStringt'
G:\qt files\myFtp-build-desktop/../myFtp/widget.cpp:12: undefined reference to `_imp___ZN4QFtp5loginERK7QStringS2_'
G:\qt files\myFtp-build-desktop/../myFtp/widget.cpp:13: undefined reference to `_imp___ZN4QFtp2cdERK7QString'
G:\qt files\myFtp-build-desktop/../myFtp/widget.cpp:14: undefined reference to `_imp___ZN4QFtp3getERK7QStringP9QIODeviceNS_12TransferTypeE'
G:\qt files\myFtp-build-desktop/../myFtp/widget.cpp:15: undefined reference to `_imp___ZN4QFtp5closeEv'
debug/widget.o:G:\qt files\myFtp-build-desktop/../myFtp/widget.cpp:31: undefined reference to `_imp___ZNK4QFtp14currentCommandEv'
debug/widget.o:G:\qt files\myFtp-build-desktop/../myFtp/widget.cpp:35: undefined reference to `_imp___ZNK4QFtp14currentCommandEv'
debug/widget.o:G:\qt files\myFtp-build-desktop/../myFtp/widget.cpp:39: undefined reference to `_imp___ZNK4QFtp14currentCommandEv'
debug/widget.o:G:\qt files\myFtp-build-desktop/../myFtp/widget.cpp:43: undefined reference to `_imp___ZNK4QFtp14currentCommandEv'
debug/widget.o:G:\qt files\myFtp-build-desktop/../myFtp/widget.cpp:51: undefined reference to `_imp___ZNK4QFtp14currentCommandEv'
debug/widget.o:G:\qt files\myFtp-build-desktop/../myFtp/widget.cpp:55: undefined reference to `_imp___ZNK4QFtp11errorStringEv'
debug/widget.o:G:\qt files\myFtp-build-desktop/../myFtp/widget.cpp:62: undefined reference to `_imp___ZNK4QFtp14currentCommandEv'
debug/widget.o:G:\qt files\myFtp-build-desktop/../myFtp/widget.cpp:66: undefined reference to `_imp___ZNK4QFtp11errorStringEv'
debug/widget.o:G:\qt files\myFtp-build-desktop/../myFtp/widget.cpp:73: undefined reference to `_imp___ZNK4QFtp14currentCommandEv'
debug/widget.o:G:\qt files\myFtp-build-desktop/../myFtp/widget.cpp:77: undefined reference to `_imp___ZNK4QFtp11errorStringEv'
debug/widget.o:G:\qt files\myFtp-build-desktop/../myFtp/widget.cpp:81: undefined reference to `_imp___ZN4QFtp7readAllEv'
debug/widget.o:G:\qt files\myFtp-build-desktop/../myFtp/widget.cpp:84: undefined reference to `_imp___ZNK4QFtp14currentCommandEv'
collect2: ld returned 1 exit status
mingw32-make[1]: Leaving directory `G:/qt files/myFtp-build-desktop'
mingw32-make: Leaving directory `G:/qt files/myFtp-build-desktop'
mingw32-make[1]: *** [debug\myFtp.exe] Error 1
mingw32-make: *** [debug] Error 2
不知什么原因，请高手指点
