佛山网站建设天博,wordpress标签订阅插件,网站是如何做的好,登封做网站Qt中postEvent和sendEvent函数部分内容参考http://blog.csdn.net/lvmengzou/article/details/65450908qt事件循环需要维护一个事件队列#xff0c;在Qt的main函数中最后一般调用QApplication::exec()成员函数来保持程序对事件队列的处理#xff0c;exec()的实质是不停调用pro…Qt中postEvent和sendEvent函数部分内容参考http://blog.csdn.net/lvmengzou/article/details/65450908qt事件循环需要维护一个事件队列在Qt的main函数中最后一般调用QApplication::exec()成员函数来保持程序对事件队列的处理exec()的实质是不停调用processEvent()函数从队列中获取事件并处理然后删除postEvent的作用就是发送一个事件到此队列中由于删除队列中事件调用delete运算符所以postEvent()传递的事件一定要是动态分配的。sendEvent()函数直接跳过事件循环队列直接调用notify()函数发送事件到目标对象并等待事件处理结果所以其传递的事件直接在栈上分配即可(postEvent()函数只负责添加事件到队列不等待事件处理结果)。sendEvent调用关系如下inline bool QCoreApplication::sendEvent(QObject *receiver, QEvent *event){ if (event) event-spont false; return self ? self-notifyInternal(receiver, event) : false; }QCoreApplication::notifyInternal(QObject * receiver, QEvent * event)QCoreApplication::notify(QObject * receiver, QEvent *event)QCoreApplicationPrivate::notify_helper(QObject * receiver, QEvent * event)最终调用receiver-event(event);PostEvent()函数只是单纯添加事件到postEventListvoid QCoreApplication::postEvent(QObject *receiver, QEvent *event){postEvent(receiver, event, Qt::NormalEventPriority);}void QCoreApplication::postEvent(QObject *receiver, QEvent *event, int priority){...QThreadData * volatile * pdata receiver-d_func()-threadData; //得到线程信息QThreadData *data *pdata;if (!data) {// posting during destruction? just delete the event to prevent a leakdelete event;return;}// lock the post event mutexdata-postEventList.mutex.lock();// if object has moved to another thread, follow itwhile (data ! *pdata) { //在这里判断receiver线程信息是否发生变化。(有可能是另外一个线程调用用receiver-moveToThread)data-postEventList.mutex.unlock();data *pdata;if (!data) {// posting during destruction? just delete the event to prevent a leakdelete event;return;}data-postEventList.mutex.lock();}//这里postEventList还是被锁着的。// if this is one of the compressible events, do compressionif (receiver-d_func()-postedEvents self self-compressEvent(event, receiver, data-postEventList)) {data-postEventList.mutex.unlock();//这个事件有可能被压缩(实际上是发现队列中有这个事件还没有被处理且这个事件是可以被压缩的例如paintevent)return;}event-posted true;receiver-d_func()-postedEvents;if (event-type() QEvent::DeferredDelete data QThreadData::current()) {// remember the current running eventloop for DeferredDelete// events posted in the receivers threadevent-d reinterpret_cast(quintptr(data-loopLevel)); //receiver即将被析构}//将事件添加到postEventList中注意这里的优先级第一个最高最后一个优先级最低if (data-postEventList.isEmpty() || data-postEventList.last().priority priority) {// optimization: we can simply append if the last event in// the queue has higher or equal prioritydata-postEventList.append(QPostEvent(receiver, event, priority));} else {// insert event in descending priority order, using upper// bound for a given priority (to ensure proper ordering// of events with the same priority)QPostEventList::iterator begin data-postEventList.begin() data-postEventList.insertionOffset,end data-postEventList.end();QPostEventList::iterator at qUpperBound(begin, end, priority);data-postEventList.insert(at, QPostEvent(receiver, event, priority));}data-canWait false;data-postEventList.mutex.unlock();//在这里解除锁//receiver所在的线程调用eventDispatcher处理postEventListif (data-eventDispatcher)data-eventDispatcher-wakeUp();}如果想查看Qt中QApplication::exec()函数是如何传递事件到目标对象并根据notify返回值和事件isAccept()的返回值决定是否传递事件到目标对象的父对象可以重载目标对象的事件处理函数并在事件处理函数中加入断点开始调试然后在可执行程序界面上触发事件处理函数程序就会在事件处理函数的断点处停止然后逐级返回查看整个调用情况从processEvent()函数到最终我们重载的事件处理函数至少有20层函数调用。(调试之前要安装Qt源码组件)
