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
在使用QT过程中,新手在QTimer,多线程,信号槽不是很了解的时候,常常容易感觉有点乱,最近自己编写了几个案例,仔细研究了一下定时器,多线程,信号槽之间的相互关系。
个人总结:
线程是程序运行的基本单位,GUI编程中,主线程既是GUI线程,其他都是子线程,在创建子线程时,个人还是建议用movethread的方式。这种方式能将整个对象的生命周期都放置到一个独立的子线程中,对象的所有操作都将在子线程中完成。很符合线程的概念。
线程之间优先采用信号槽的方式通讯。保证线程安全的同时,也能保证一些需要时序控制的过程的安全可控运行。省去了线程同步的麻烦。
信号槽之所以能省去线程同步的麻烦,正是因为事件循环的作用,信号发送到子线程后,将按发送先后的顺序依次插入到子线程的事件队列中,当前面的事件处理完成后,依次执行后续事件。这个方式就能起到线程同步的作用。
而通过movethread的创建的子线程,当start的时候,默认是会开启一个子线程的事件循环。在非直接连接的信号槽绑定后,所有的信号都将在子线程的事件循环中依次完成。
而定时器的运行,也是在线程的事件循环中实现的,当timeout信号发出后,在创建该定时器的线程中将触发对应槽函数。也即在哪个线程创建,对应的timeout就在哪个线程的事件循环中执行。
线程中的程序的执行是串行的,所以信号槽,定时器触发都是按其信号的发送时间来顺序执行。
正是因为这样,当有多个定时器时,对应的槽函数的执行时间就一定得注意了,最好不要超过定时器的设置时间,因为一旦超过,定时器设置的定时时间将不是自己所设定的定时周期执行。很重要。
但是当在子线程中执行while循环时,由于线程是串行工作,没有退出while时,将阻塞事件循环中的其他所有事件。这时需要好好考虑子线程的作用,以及需要完成的工作都有哪些,以及相关动作是否适合放置在1个子线程中,是否还需要再次创建子线程,都是需要考虑的。在while 中放置一个QCoreApplication::processEvents();来人为触发事件。可以在一些场景下,保证while循环运行同时,响应其他所有事件,但是其后也要跟一个sleep指令,并且时间要合适,才能保证其他事件的及时响应。个人建议不要小于10ms的sleep时间。
当循环时间小于槽函数时间时:
#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(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。
当在主程序中添加一个for循环后
#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);for (int i=0;i<100;++i){std::cout << QTime::currentTime().toString("HH:mm:ss zzz").toStdString() << " Main"<<i << std::endl;QThread::msleep(100);}return a.exec();
}
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 <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);for (int i=0;i<100;++i){std::cout << QTime::currentTime().toString("HH:mm:ss zzz").toStdString() << " Main"<<i << std::endl;//适当的位置,插入一个processEvents,保证事件循环被处理QCoreApplication::processEvents();QThread::msleep(100);}return a.exec();
}
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 <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);
}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"<<i << std::endl;//适当的位置,插入一个processEvents,保证事件循环被处理//QCoreApplication::processEvents();QThread::msleep(100);}}};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);TestThread1* test1{nullptr};test1 = new TestThread1;test1->start();// for (int i=0;i<100;++i)// {// std::cout << QTime::currentTime().toString("HH:mm:ss zzz").toStdString() << " Main"<<i << std::endl;适当的位置,插入一个processEvents,保证事件循环被处理//QCoreApplication::processEvents();// QThread::msleep(100);// }return a.exec();
}
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 <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);
}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"<<i << std::endl;//适当的位置,插入一个processEvents,保证事件循环被处理QCoreApplication::processEvents();QThread::msleep(100);}}};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);TestThread1* test1{nullptr};test1 = new TestThread1;test1->start();// for (int i=0;i<100;++i)// {// std::cout << QTime::currentTime().toString("HH:mm:ss zzz").toStdString() << " Main"<<i << std::endl;适当的位置,插入一个processEvents,保证事件循环被处理//QCoreApplication::processEvents();// QThread::msleep(100);// }return a.exec();
}
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。