将头文件添加到add-executable()中
cmake_minimum_required(VERSION 3.12)
project(SGTK3application2 C)
set(CMAKE_C_STANDARD 11)
find_package(PkgConfig REQUIRED)
pkg_check_modules(GTK3 REQUIRED gtk+-3.0)
include_directories(${GTK3_INCLUDE_DIRS})
link_directories(${GTK3_LIBRARY_DIRS})
add_definitions(${GTK3_CFLAGS_OTHER})
add_executable(SGTK3application2 main.c exampleapp.h exampleapp.c exampleappwin.h exampleappwin.c)
target_link_libraries(SGTK3application2 ${GTK3_LIBRARIES})