c++ - Qthread 中的运行函数 - 应用程序将挂起

Question

我在 QT 中使用线程时遇到了一些问题。

#include <QCoreApplication>

#include "handler.hpp"

int main(int argc, char *argv[]) {
    QCoreApplication a(argc, argv);

    Handler* handler = new Handler();
    handler->StartThread();

    return a.exec();
}

我期望的是，使用 handler->StartThread() 语句，我的线程中的函数开始编写调试消息，一旦处理程序中的内部计时器完成，我就会得到漂亮的行 [Press ...] 然后返回代码0。然而这没有发生。我得到的是:

I WORK...            ( 0x1540 )
Worker has finished. ( 0x6f4  )
I WORK...            ( 0x1540 )
Worker has finished. ( 0x6f4  )
I WORK...            ( 0x1540 )
Worker has finished. ( 0x6f4  )
I WORK...            ( 0x1540 )
Worker has finished. ( 0x6f4  )
Thread stopped.

当然，当我停止执行应用程序时，返回码是:-1073741510。显然，零不是那么好。无论如何，这是应用程序代码的其余部分:Handler.hpp

#ifndef HANDLER_HPP
#define HANDLER_HPP

#include <QObject>
#include <QThread>
#include <QDebug>
#include <QTimer>

#include "testclass.hpp"

class Handler : public QObject
{
    Q_OBJECT
public:
    Handler();
    ~Handler();
    void StartThread();

public slots:
    void functionFinished();
    void threadTerminated();

private:
    QTimer*     shutdown;
    QTimer*     timer;
    QThread*    thread;
    MyClass*    worker;
};

#endif // HANDLER_HPP

Handler.cpp

#include "handler.hpp"

Handler::Handler() {
    shutdown        = new QTimer();
    thread          = new QThread();
    timer           = new QTimer();
    worker          = new MyClass();

    worker->moveToThread(thread);
    QObject::connect(thread, SIGNAL(started()), worker, SLOT(runAgain()));
    QObject::connect(timer, SIGNAL(timeout()), worker, SLOT(runAgain()));
    QObject::connect(worker, SIGNAL(iFinished()), this, SLOT(functionFinished()));
    QObject::connect(shutdown, SIGNAL(timeout()), thread, SLOT(quit()));
    QObject::connect(thread, SIGNAL(finished()), this, SLOT(threadTerminated()));

    shutdown->start(20000);
}

Handler::~Handler() {
    QObject::disconnect(thread, SIGNAL(started()), worker, SLOT(runAgain()));
    QObject::disconnect(timer, SIGNAL(timeout()), worker, SLOT(runAgain()));
    QObject::disconnect(worker, SIGNAL(iFinished()), this, SLOT(functionFinished()));
    QObject::disconnect(shutdown, SIGNAL(timeout()), thread, SLOT(quit()));
    QObject::disconnect(thread, SIGNAL(finished()), this, SLOT(threadTerminated()));

    if (shutdown != 0) {
        delete shutdown;
        shutdown = 0;
    }

    if (timer != 0) {
        delete timer;
        timer = 0;
    }

    if (thread != 0) {
        delete thread;
        thread = 0;
    }

    if (worker != 0) {
        delete worker;
        worker = 0;
    }
}

void Handler::functionFinished() {
    qDebug() << "Worker has finished. (" << QThread::currentThreadId() << ")";
    timer->start(5000);
}

void Handler::threadTerminated() {
    qDebug() << "Thread stopped.";
}

void Handler::StartThread() {
    thread->start();
}

MyClass( header - testclass.hpp)

#ifndef TESTCLASS_HPP
#define TESTCLASS_HPP

#include <QTimer>
#include <QObject>

class MyClass : public QObject
{
    Q_OBJECT
public:
    MyClass();

public slots:
    void runAgain();

signals:
    void iFinished();

private:
    void doWork();

};

#endif // TESTCLASS_HPP

MyClass 源代码 - testclass.cpp

#include "testclass.hpp"

#include <QThread>
#include <QDebug>

MyClass::MyClass() {

}

void MyClass::runAgain() {
    doWork();
}

void MyClass::doWork() {
    qDebug() << "I WORK...\t(" << QThread::currentThreadId() << ")";
    emit iFinished();
}

我以前读到过，直接从 QThread 继承要在线程内运行的类不是一个好主意，所以我想出了这个解决方案，但它仍然很可疑，尽管它非常好。我愿意接受任何建议，这是我第一次使用 QT，所以现在学习比以后感到遗憾更好。

糟糕，我忘记了具体的实际问题。为什么执行不以良好的退出代码 0 结束？

Answer 1

What I expect is that with handler->StartThread() statement the function within my thread start to write debug messages and once the internal timer within handler finishes I get the nice line [Press ...] and then a return code of 0. However this is not happening.

您没有得到“[Press ...]”命令提示符的原因是 QCoreApplication 及其 exec() 调用。作为Qt docs state :-

Enters the main event loop and waits until exit() is called

因此，您已经创建了第二个线程，将其设置为执行一些工作并完成，但主线程仍在运行。您需要退出主线程。

And of course when I stop the execution of the application, the return code is: -1073741510

听起来您正在用“Ctrl+C”之类的东西杀死主线程。当您的第二个线程完成并清理完毕时调用 QCoreApplication::exit() 应该会有所帮助。