编译Qt时遇到”error LNK2001: 无法解析的外部符号“

解决办法：运行QT的命令行工具

From a command prompt, change the directory to hello, and type
qmake -project
to create a platform-independent project file (hello.pro), and then type
qmake hello.pro

If you are using Microsoft Visual C++ with a commercial version of Qt, you will need to run nmake instead of make.
Alternatively, you can create a Visual Studio project file from hello.pro by typing
qmake -tp vc hello.pro