我正在编写一个程序,该程序每REFRESH_RATE
毫秒从相机捕获一次图像,然后将其发送到某种计算算法。我决定使用来设置该算法的启动时间QThread
,但是该算法正在主线程上运行,因为我需要在此线程之前创建对象。无论如何,这很好。当我尝试关闭第二个线程时,麻烦就开始了。这是代码。
相机:
class Camera : public QMainWindow
{
Q_OBJECT
public:
Camera(QWidget *parent = 0){
AlgoQThread = new QThread;
myAlgoThreadWorker = new AlgoThreadWorker( (Camera *) this );
myAlgoThreadWorker->moveToThread(AlgoQThread);
//Launch The thread
connect(AlgoQThread, SIGNAL(started()), myAlgoThreadWorker, SLOT(process()));
connect(myAlgoThreadWorker, SIGNAL(finished()), AlgoQThread, SLOT(quit()));
// The line meant to stop the thread at next loop
connect(this, SIGNAL(stopAlgoThread()), myAlgoThreadWorker, SLOT(stopThread()));
connect(myAlgoThreadWorker, SIGNAL(finished()), myAlgoThreadWorker, SLOT(deleteLater()));
connect(AlgoQThread, SIGNAL(finished()), AlgoQThread, SLOT(deleteLater()));
AlgoQThread->start();
}
private slots:
void errorString(QString error);
//This function is triggered by a signal sent by the method called in AlgoThreadWoker::process()
void some_algorithm(){
...
emit stopAlgoThread();
}
signals:
void stopAlgoThread();
private:
QThread * AlgoQThread;
AlgoThreadWorker * myAlgoThreadWorker;
};
algoThreadWorker:
class AlgoThreadWorker : public QObject
{
Q_OBJECT
public:
AlgoThreadWorker(Camera * context){
parentCamera = context;
}
Camera* parentCamera;
public slots:
void process(){
while(1){
QMutexLocker locker(&m_mutex);
if (t_stop) break;
parentCamera->isCapturingImage = true;
//This triggers the some_algorithm() using a signal sent by imageCapture from main Thread
parentCamera->imageCapture->capture();
//Wait REFRESH_RATE millisecondes
Sleep(REFRESH_RATE);
}
//Ends the thread
emit finished();
}
private slots:
void stopThread(){
QMutexLocker locker(&m_mutex);
t_stop = true;
};
signals:
void finished();
void error(QString);
private:
bool t_stop;
QMutex m_mutex;
};
而且,正如您可能已经预见到的那样,它是行不通的。我可以毫无问题地启动some_algorithm()
,但是我无法结束线程。该stopThread()
插槽甚至还没有启动,我已经测试过了。
由于您在while循环中忙于等待,因此事件循环永远不会有机会处理接收到的信号。
qApp->processEvents()
将控件交给事件循环,以处理等待的作业。
请注意,通常您不必自己调用它,Qt会为您调用它。在您的情况下,这是必要的,因为您有一个无限循环,这会阻止Qt执行其工作。
解决方案:
void process(){
while(1){
qApp->processEvents();
^^^^^^^^^^^^^^^^^^^^^^
.....
}
//Ends the thread
emit finished();
}
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