目录

QTimer运行程序在控制台中实现： 

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

---

QTimer运行程序在控制台中实现： 

#include <QtCore/QCoreApplication>
#include <QTimer>
#include <QThread>
#include <iostream>
#include <QObject>
#include <QTime>

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 <QtCore/QCoreApplication>
#include <QTimer>
#include <QThread>
#include <iostream>
#include <QObject>
#include <QTime>

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 <QtCore/QCoreApplication>
#include <QTimer>
#include <QThread>
#include <iostream>
#include <QObject>
#include <QTime>

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 <QtCore/QCoreApplication>
#include <QTimer>
#include <QThread>
#include <iostream>
#include <QObject>
#include <QTime>

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。