1 #include <qapplication.h>
 2 #include <qpushbutton.h>
 3 #include <qfont.h>
 4
 5 int main( int argc, char **argv )
 6 {
 7  QApplication a( argc, argv );
 8  QPushButton quit( "Quit", 0 );
 9  quit.resize( 75, 30 );
10  quit.setFont( QFont( "Times", 18, QFont::Bold ) );
11  QObject::connect( &quit, SIGNAL(clicked()), &a, SLOT(quit()) );
12  quit.show();
13  return a.exec();
14 }

1 QApplication : QCoreApplication : QObject

1 QApplication::QApplication(int &argc, char **argv)
2     : QCoreApplication(*new QApplicationPrivate(argc, argv, GuiClient))
3 { Q_D(QApplication); d->construct(); }

1 #define Q_D(Class) Class##Private * const d = d_func()

1 QApplicationPrivate * const d = d_func();

1 #define Q_Q(Class) Class * const q = q_func()

1 QApplicationPrivate::construct()；

 1 void QApplicationPrivate::construct()
 2 {
 3     initResources();          // 初始化资源
 4
 5     qt_is_gui_used = (qt_appType != QApplication::Tty);
 6     process_cmdline();     // 扫描分析命令行参数
 7     // Must be called before initialize()
 8     qt_init(  this, qt_appType  );  // 在initialize()之前必须执行的初始化，例如色彩、字体、键盘等
 9     initialize();
10     eventDispatcher->startingUp();
11
12 }

1 QCoreApplication::QCoreApplication(QCoreApplicationPrivate &p)
2     : QObject(p, 0)
3 {
4     init();
5     // note: it is the subclasses' job to call
6     // QCoreApplicationPrivate::eventDispatcher->startingUp();
7 }

 1 void QCoreApplication::init()
 2 {
 3     Q_D(QCoreApplication);
 4
 5     // Get the application name/instance if qWinMain() was not invoked
 6     set_winapp_name();  // 设置应用程序的名字
 7
 8     Q_ASSERT_X(!self, "QCoreApplication", "there should be only one application object");
 9     QCoreApplication::self = this;
10
11     QThread::initialize();  // 初始化线程
12
13     // use the event dispatcher created by the app programmer (if any)
14     if (!QCoreApplicationPrivate::eventDispatcher)
15         QCoreApplicationPrivate::eventDispatcher = d->threadData->eventDispatcher;
16     // otherwise we create one
17     if (!QCoreApplicationPrivate::eventDispatcher)
18         d->createEventDispatcher();  // 生成事件分发
19     Q_ASSERT(QCoreApplicationPrivate::eventDispatcher != 0);
20
21     if (!QCoreApplicationPrivate::eventDispatcher->parent())
22         QCoreApplicationPrivate::eventDispatcher->moveToThread(d->threadData->thread);
23
24     d->threadData->eventDispatcher = QCoreApplicationPrivate::eventDispatcher;
25
26     if (!coreappdata()->app_libpaths) {
27         // make sure that library paths is initialized
28         libraryPaths();  // 确认或设定DLL库的路径
29     } else {
30         d->appendApplicationPathToLibraryPaths();
31     }
32
33     qt_startup_hook();  // 目前是空函数
34 }