Qt source code compilation error:
1. Source code path contains Chinese font
2. No such file or directory can be found at compile time.
Solution:
1. Change to English path
2. When compiling the source code, add QT += widgets at the bottom of the project file. Pro.

Baidu Answer Question 2:
Write in the pro qt + = widgets QtWidget this module, introduced said, qmake will help you to generate a makefile, set up the include path and lib path, when the link set libs.
include

QApplication> Only the declaration is introduced, but there is no lib, so the link will fail.