做办公设备网站/商丘seo教程

Qt程序是基于事件驱动的，在每个GUI主线程的main函数后面都有return a.exec();

实际上就是使Qt程序进入事件循环。

下面我们看看Qt exec()的源码：

int QCoreApplication::exec()
{if (!QCoreApplicationPrivate::checkInstance("exec"))return -1;//获取线程数据QThreadData *threadData = self->d_func()->threadData;//判断是否在主线程创建if (threadData != QThreadData::current()) {qWarning("%s::exec: Must be called from the main thread", self->metaObject()->className());return -1;}//判断eventLoop是否已经创建if (!threadData->eventLoops.isEmpty()) {qWarning("QCoreApplication::exec: The event loop is already running");return -1;}threadData->quitNow = false;QEventLoop eventLoop;self->d_func()->in_exec = true;//创建eventLoopint returnCode = eventLoop.exec();threadData->quitNow = false;if (self) {self-&g