QT中QTimer的循环时间与槽函数执行时间分析，以及在事件循环中触发

目录

当循环时间小于槽函数时间时： 

当循环间隔时间大于槽函数时间时：

当存在两个定时器器，其中一个还是间隔100ms，另一个间隔1000ms： 

当两个定时器的循环周期大于槽函数执行时间时

当在主程序中添加一个for循环后 

当在for循环中加上人为触发其他事件QCoreApplication::processEvents() 后

当把for循环放到子线程中运行时 

当在子线程中定义定时器时 

---

当循环时间小于槽函数时间时： 

#include 
#include 
#include 
#include 
#include 
#include 

void timer1()
{
    std::cout << QTime::currentTime().toString("HH:mm:ss zzz").toStdString() <<"  1" << std::endl;
    QThread::msleep(1000);
    std::cout << QTime::currentTime().toString("HH:mm:ss zzz").toStdString() <<"  2" << std::endl;
    QThread::msleep(1000);
    std::cout << QTime::currentTime().toString("HH:mm:ss zzz").toStdString() <<"  3" << std::endl;
    QThread::msleep(1000);
	std::cout << QTime::currentTime().toString("HH:mm:ss zzz").toStdString() <<"  4" << std::endl;
	QThread::msleep(1000);
	std::cout << QTime::currentTime().toString("HH:mm:ss zzz").toStdString() <<"  5" << std::endl;
	QThread::msleep(1000);
	std::cout << QTime::currentTime().toString("HH:mm:ss zzz").toStdString() <<"  6" << std::endl;
}


int main(int argc, char *argv[])
{
    QCoreApplication a(argc, argv);
    QTimer timeTest;
    timeTest.setTimerType(Qt::PreciseTimer);
    QObject::connect(&timeTest, &QTimer::timeout, [=]() {timer1(); });
    
    timeTest.start(100);

    return a.exec();
}

执行结果： 

结果分析：

QTimer 设置的循环时间小于槽函数的执行时间时，当循环时间结束时，并不会将槽函数中断，而是等槽函数运行结束后，直接再次进入，中间没有间隔时间。

当循环间隔时间大于槽函数时间时：

#include 
#include 
#include 
#include 
#include 
#include 

void timer1()
{
    std::cout << QTime::currentTime().toString("HH:mm:ss zzz").toStdString() <<"  1" << std::endl;
    QThread::msleep(1000);
    std::cout << QTime::currentTime().toString("HH:mm:ss zzz").toStdString() <<"  2" << std::endl;
    QThread::msleep(1000);
    std::cout << QTime::currentTime().toString("HH:mm:ss zzz").toStdString() <<"  3" << std::endl;
    QThread::msleep(1000);
	std::cout << QTime::currentTime().toString("HH:mm:ss zzz").toStdString() <<"  4" << std::endl;
	QThread::msleep(1000);
	std::cout << QTime::currentTime().toString("HH:mm:ss zzz").toStdString() <<"  5" << std::endl;
	QThread::msleep(1000);
	std::cout << QTime::currentTime().toString("HH:mm:ss zzz").toStdString() <<"  6" << std::endl;
}


int main(int argc, char *argv[])
{
    QCoreApplication a(argc, argv);
    QTimer timeTest;
    timeTest.setTimerType(Qt::PreciseTimer);
    QObject::connect(&timeTest, &QTimer::timeout, [=]() {timer1(); });
    
    timeTest.start(7000);

    return a.exec();
}

 结果分析：

间隔时间都比较准。每次的间隔时间也不会存在累计误差。

当存在两个定时器器，其中一个还是间隔100ms，另一个间隔1000ms： 

#include 
#include 
#include 
#include 
#include 
#include 

void timer1()
{
    std::cout << QTime::currentTime().toString("HH:mm:ss zzz").toStdString() <<"  1" << std::endl;
    QThread::msleep(1000);
    std::cout << QTime::currentTime().toString("HH:mm:ss zzz").toStdString() <<"  2" << std::endl;
    QThread::msleep(1000);
    std::cout << QTime::currentTime().toString("HH:mm:ss zzz").toStdString() <<"  3" << std::endl;
    QThread::msleep(1000);
	std::cout << QTime::currentTime().toString("HH:mm:ss zzz").toStdString() <<"  4" << std::endl;
	QThread::msleep(1000);
	std::cout << QTime::currentTime().toString("HH:mm:ss zzz").toStdString() <<"  5" << std::endl;
	QThread::msleep(1000);
	std::cout << QTime::currentTime().toString("HH:mm:ss zzz").toStdString() <<"  6" << std::endl;
}

void timer2()
{
	std::cout << QTime::currentTime().toString("HH:mm:ss zzz").toStdString() << "  Timer2" << std::endl;
	//QThread::msleep(1000);
}
int main(int argc, char *argv[])
{
    QCoreApplication a(argc, argv);
    QTimer timeTest,timeTest2;
    timeTest.setTimerType(Qt::PreciseTimer);
    timeTest2.setTimerType(Qt::PreciseTimer);
    QObject::connect(&timeTest, &QTimer::timeout, [=]() {timer1(); });
    QObject::connect(&timeTest2, &QTimer::timeout, [=]() {timer2(); });

    timeTest.start(100);
    timeTest2.start(1000);
    return a.exec();
}

结果分析：

第一个100ms的定时器优先抢占触发事件，当执行完两个对应槽函数后，第二个1000ms的定时器才执行一次槽函数。 

100ms触发

1s-2s-3s-4s-5s-6s-1s-2s-3s-4s-5s-6s-第二个触发-

总结：在不能确定定时器槽函数执行时间时，如果还存在其他定时器，当第一个定时器执行超时时，将直接影响第二个定时器的执行周期。所以在这种应用中，尽量避免定时器的循环周期小于槽函数执行时长。

当两个定时器的循环周期大于槽函数执行时间时

#include 
#include 
#include 
#include 
#include 
#include 

void timer1()
{
    std::cout << QTime::currentTime().toString("HH:mm:ss zzz").toStdString() <<"  1" << std::endl;
    QThread::msleep(1000);
    std::cout << QTime::currentTime().toString("HH:mm:ss zzz").toStdString() <<"  2" << std::endl;
    QThread::msleep(1000);
    std::cout << QTime::currentTime().toString("HH:mm:ss zzz").toStdString() <<"  3" << std::endl;
    QThread::msleep(1000);
	std::cout << QTime::currentTime().toString("HH:mm:ss zzz").toStdString() <<"  4" << std::endl;
	QThread::msleep(1000);
	std::cout << QTime::currentTime().toString("HH:mm:ss zzz").toStdString() <<"  5" << std::endl;
	QThread::msleep(1000);
	std::cout << QTime::currentTime().toString("HH:mm:ss zzz").toStdString() <<"  6" << std::endl;
}

void timer2()
{
	std::cout << QTime::currentTime().toString("HH:mm:ss zzz").toStdString() << "  Timer2" << std::endl;
	//QThread::msleep(1000);
}
int main(int argc, char *argv[])
{
    QCoreApplication a(argc, argv);
    QTimer timeTest,timeTest2;
    timeTest.setTimerType(Qt::PreciseTimer);
    timeTest2.setTimerType(Qt::PreciseTimer);
    QObject::connect(&timeTest, &QTimer::timeout, [=]() {timer1(); });
    QObject::connect(&timeTest2, &QTimer::timeout, [=]() {timer2(); });

    timeTest2.start(1000);
    timeTest.start(7000);
   
    return a.exec();
}

结果分析：

当两个定时器在同一个线程中时，两个定时器是按单线程串行的方式执行，当其中一个定时器触发时，必须等待当前定时器执行完成后，才有可能执行另外的定时器，两个定时器的优先级感觉是随机的。这也就解释了为什么上个案例定时周期不稳定的原因。

当在主程序中添加一个for循环后 

#include 
#include 
#include 
#include 
#include 
#include 

void timer1()
{
    std::cout << QTime::currentTime().toString("HH:mm:ss zzz").toStdString() <<"  1" << std::endl;
    QThread::msleep(1000);
    std::cout << QTime::currentTime().toString("HH:mm:ss zzz").toStdString() <<"  2" << std::endl;
    QThread::msleep(1000);
    std::cout << QTime::currentTime().toString("HH:mm:ss zzz").toStdString() <<"  3" << std::endl;
    QThread::msleep(1000);
	std::cout << QTime::currentTime().toString("HH:mm:ss zzz").toStdString() <<"  4" << std::endl;
	QThread::msleep(1000);
	std::cout << QTime::currentTime().toString("HH:mm:ss zzz").toStdString() <<"  5" << std::endl;
	QThread::msleep(1000);
	std::cout << QTime::currentTime().toString("HH:mm:ss zzz").toStdString() <<"  6" << std::endl;
}

void timer2()
{
	std::cout << QTime::currentTime().toString("HH:mm:ss zzz").toStdString() << "  Timer2" << std::endl;
	//QThread::msleep(1000);
}
int main(int argc, char *argv[])
{
    QCoreApplication a(argc, argv);
    QTimer timeTest,timeTest2;
    timeTest.setTimerType(Qt::PreciseTimer);
    timeTest2.setTimerType(Qt::PreciseTimer);
    QObject::connect(&timeTest, &QTimer::timeout, [=]() {timer1(); });
    QObject::connect(&timeTest2, &QTimer::timeout, [=]() {timer2(); });

    timeTest2.start(1000);
    timeTest.start(7000);

    for (int i=0;i<100;++i)
    {
        std::cout << QTime::currentTime().toString("HH:mm:ss zzz").toStdString() << "  Main"<

结论：两个定时器必须在for循环执行完成后，才能触发。再次 证明定时器在主线程中是以串行的方式执行。 当for循环没有结束时，定时器的timeout信号在线程中是阻塞的状况，是无法响应对应槽函数的。

当在for循环中加上人为触发其他事件QCoreApplication::processEvents() 后

#include 
#include 
#include 
#include 
#include 
#include 

void timer1()
{
    std::cout << QTime::currentTime().toString("HH:mm:ss zzz").toStdString() <<"  1" << std::endl;
    QThread::msleep(1000);
    std::cout << QTime::currentTime().toString("HH:mm:ss zzz").toStdString() <<"  2" << std::endl;
    QThread::msleep(1000);
    std::cout << QTime::currentTime().toString("HH:mm:ss zzz").toStdString() <<"  3" << std::endl;
    QThread::msleep(1000);
	std::cout << QTime::currentTime().toString("HH:mm:ss zzz").toStdString() <<"  4" << std::endl;
	QThread::msleep(1000);
	std::cout << QTime::currentTime().toString("HH:mm:ss zzz").toStdString() <<"  5" << std::endl;
	QThread::msleep(1000);
	std::cout << QTime::currentTime().toString("HH:mm:ss zzz").toStdString() <<"  6" << std::endl;
}

void timer2()
{
	std::cout << QTime::currentTime().toString("HH:mm:ss zzz").toStdString() << "  Timer2" << std::endl;
	//QThread::msleep(1000);
}
int main(int argc, char *argv[])
{
    QCoreApplication a(argc, argv);
    QTimer timeTest,timeTest2;
    timeTest.setTimerType(Qt::PreciseTimer);
    timeTest2.setTimerType(Qt::PreciseTimer);
    QObject::connect(&timeTest, &QTimer::timeout, [=]() {timer1(); });
    QObject::connect(&timeTest2, &QTimer::timeout, [=]() {timer2(); });

    timeTest2.start(1000);
    timeTest.start(7000);

    for (int i=0;i<100;++i)
    {
        std::cout << QTime::currentTime().toString("HH:mm:ss zzz").toStdString() << "  Main"<

结论：当添加了 QCoreApplication::processEvents();后 在每次的for循环中都触发一次进程事件，保证timeout事件触发，是可行的。

当把for循环放到子线程中运行时 

#include 
#include 
#include 
#include 
#include 
#include 

void timer1()
{
    std::cout << QTime::currentTime().toString("HH:mm:ss zzz").toStdString() <<"  1" << std::endl;
    QThread::msleep(1000);
    std::cout << QTime::currentTime().toString("HH:mm:ss zzz").toStdString() <<"  2" << std::endl;
    QThread::msleep(1000);
    std::cout << QTime::currentTime().toString("HH:mm:ss zzz").toStdString() <<"  3" << std::endl;
    QThread::msleep(1000);
	std::cout << QTime::currentTime().toString("HH:mm:ss zzz").toStdString() <<"  4" << std::endl;
	QThread::msleep(1000);
	std::cout << QTime::currentTime().toString("HH:mm:ss zzz").toStdString() <<"  5" << std::endl;
	QThread::msleep(1000);
	std::cout << QTime::currentTime().toString("HH:mm:ss zzz").toStdString() <<"  6" << std::endl;
}

void timer2()
{
	std::cout << QTime::currentTime().toString("HH:mm:ss zzz").toStdString() << "  Timer2" << std::endl;
	//QThread::msleep(1000);
}

class TestThread1:public QThread
{

    //Q_OBJECT
public:
     TestThread1() {

    };
    ~TestThread1() {

    };

    void run()
    {
	   for (int i=0;i<1000;++i)
	  {
	      std::cout << QTime::currentTime().toString("HH:mm:ss zzz").toStdString() << "  subThread"<start();


  //  for (int i=0;i<100;++i)
  //  {
  //      std::cout << QTime::currentTime().toString("HH:mm:ss zzz").toStdString() << "  Main"<

 结论：当在子线程中运行时，两个定时器能正常按预想的方式运行

当在子线程中定义定时器时 

#include 
#include 
#include 
#include 
#include 
#include 

void timer1()
{
    std::cout << QTime::currentTime().toString("HH:mm:ss zzz").toStdString() <<"  1" << std::endl;
    QThread::msleep(1000);
    std::cout << QTime::currentTime().toString("HH:mm:ss zzz").toStdString() <<"  2" << std::endl;
    QThread::msleep(1000);
    std::cout << QTime::currentTime().toString("HH:mm:ss zzz").toStdString() <<"  3" << std::endl;
    QThread::msleep(1000);
	std::cout << QTime::currentTime().toString("HH:mm:ss zzz").toStdString() <<"  4" << std::endl;
	QThread::msleep(1000);
	std::cout << QTime::currentTime().toString("HH:mm:ss zzz").toStdString() <<"  5" << std::endl;
	QThread::msleep(1000);
	std::cout << QTime::currentTime().toString("HH:mm:ss zzz").toStdString() <<"  6" << std::endl;
}

void timer2()
{
	std::cout << QTime::currentTime().toString("HH:mm:ss zzz").toStdString() << "  Timer2" << std::endl;
	//QThread::msleep(1000);
}

void timer3()
{
	std::cout << QTime::currentTime().toString("HH:mm:ss zzz").toStdString() << "  subThreadTime3_1" << std::endl;
	QThread::msleep(1000);
	std::cout << QTime::currentTime().toString("HH:mm:ss zzz").toStdString() << "  subThreadTime3_2" << std::endl;
	QThread::msleep(1000);
	std::cout << QTime::currentTime().toString("HH:mm:ss zzz").toStdString() << "  subThreadTime3_3" << std::endl;
	QThread::msleep(1000);
	std::cout << QTime::currentTime().toString("HH:mm:ss zzz").toStdString() << "  subThreadTime3_4" << std::endl;
	QThread::msleep(1000);
	std::cout << QTime::currentTime().toString("HH:mm:ss zzz").toStdString() << "  subThreadTime3_5" << std::endl;
	QThread::msleep(1000);
	std::cout << QTime::currentTime().toString("HH:mm:ss zzz").toStdString() << "  subThreadTime3_6" << std::endl;
}

void timer4()
{
	std::cout << QTime::currentTime().toString("HH:mm:ss zzz").toStdString() << "  subThreadTimer4" << std::endl;
	//QThread::msleep(1000);
}

class TestThread1:public QThread
{

    //Q_OBJECT
public:
     TestThread1() {

    };
    ~TestThread1() {

    };

    void run()
    {

        QTimer time3;
        QTimer time4;
		time3.setTimerType(Qt::PreciseTimer);
		time4.setTimerType(Qt::PreciseTimer);
		QObject::connect(&time3, &QTimer::timeout, [=]() {timer3(); });
		QObject::connect(&time4, &QTimer::timeout, [=]() {timer4(); });

		time3.start(1000);
		time4.start(7000);
	   for (int i=0;i<1000;++i)
	  {
	      std::cout << QTime::currentTime().toString("HH:mm:ss zzz").toStdString() << "  subThread"<start();


  //  for (int i=0;i<100;++i)
  //  {
  //      std::cout << QTime::currentTime().toString("HH:mm:ss zzz").toStdString() << "  Main"<

结论：当在子线程中定义定时器时，现象跟在主线程的现象一致。 

QCoreApplication::processEvents();
          QThread::msleep(100); 这暂停很关键，不同的暂停时间，对其他事件的影响很大，如果没有这个暂停时间，:processEvents()将无效，暂停时间越短，其他事件执行的几率就越小。在实际的应用中需要是个合适的延时。