QThread - 调用另一个线程的方法答案

【问题标题】：QThread - Call a method of another threadQThread - 调用另一个线程的方法
【发布时间】：2014-03-09 23:27:54
【问题描述】：

我正在尝试使用invokeMethod 调用另一个线程（不是Main）的方法。不幸的是，这会使应用程序在尝试执行 invokeMethod 时立即崩溃！

我是不是弄错了什么？

// main.cpp

#include <QtCore>
#include "entrypointclass.h"
int main(int argc, char *argv[])
{
    QCoreApplication a(argc, argv);

    qDebug() << a.thread()->currentThreadId() << " - Application started.";

    EntryPointClass entryPoint;
    entryPoint.runInNewThread();
    return a.exec();
}

//入口点.h

#ifndef ENTRYPOINTCLASS_H
#define ENTRYPOINTCLASS_H

#include "worker.h"
#include <QtCore>

class EntryPointClass : public QObject
{
    Q_OBJECT
public:
    EntryPointClass();
    ~EntryPointClass();
    void runInNewThread();
public slots:
    void timeoutExpired();
private:
    Worker* m_Worker;
    QThread* m_Thread;
};

#endif // ENTRYPOINTCLASS_H

//入口点.cpp

#include <QTCore>
#include "entrypointclass.h"
#include "Worker.h"

EntryPointClass::EntryPointClass()
{
    qDebug() << "EntryPointClass created";



}

EntryPointClass::~EntryPointClass()
{
    qDebug() << "EntryPointClass destroyed";
}

void EntryPointClass::runInNewThread()
{
    QThread* m_Thread = new QThread;
    Worker* m_Worker = new Worker();


    connect(m_Thread, SIGNAL(started()), m_Worker, SLOT(doSomething()));
    connect(m_Worker, SIGNAL(finished()), m_Thread, SLOT(quit()));
    connect(m_Thread, SIGNAL(finished()), m_Thread, SLOT(deleteLater()));
    connect(m_Thread, SIGNAL(finished()), m_Worker, SLOT(deleteLater()));

    QTimer* timer = new QTimer;
    timer->setSingleShot(true);

    //bool bOK = connect(timer, SIGNAL(timeout()), m_Worker, SLOT(closeWorker()), Qt::BlockingQueuedConnection);

    connect(timer, SIGNAL(timeout()), this, SLOT(timeoutExpired()));

    m_Worker->moveToThread(m_Thread);
    m_Thread->start();
    timer->start(5000);

}

void EntryPointClass::timeoutExpired()
{
    qDebug() << "timeout expired";
    if (m_Worker != NULL)
    {
        QMetaObject::invokeMethod(m_Worker, "closeWorker", Qt::QueuedConnection);
    }
}

// Worker.h

#ifndef WORKER_H
#define WORKER_H

#include <QtCore>

class Worker : public QObject
{
    Q_OBJECT
public:
    Worker();
    ~Worker();

public slots:
    void doSomething();
    void closeWorker();

private:
    bool m_bAbort;
    QMutex m_mutex;


signals:
    void finished();
};

#endif // WORKER_H

// Worker.cpp

#include "worker.h"
#include <unistd.h>
#include "QTcore"

Worker::Worker()
    : m_mutex()
{
    qDebug() << this->thread()->currentThreadId() << "Worker created";
    m_bAbort = false;
    //qDebug() << QString("Thread %1 - Worker created").arg("");//this->thread()->currentThreadId());
}

Worker::~Worker()
{
    qDebug() << this->thread()->currentThreadId() << "Worker destroyed";

}

void Worker::doSomething()
{
    while(!m_bAbort)
    {
        sleep(2);
        qDebug() << this->thread()->currentThreadId() << "Do Something!";
    }

    emit finished();
}

void Worker::closeWorker()
{
    qDebug() << this->thread()->currentThreadId() << "closeWorker triggered!";
    QMutexLocker mutexLocker(&m_mutex);
    m_bAbort = true;
}

【问题讨论】：

QtQueuedConnection 使方法在目标线程的事件循环中被调用。由于您停留在 while 循环 doSomething() 中，因此您的线程永远不会到达事件循环中的 close-worker 调用。您可以尝试调用processEvents() 或直接在源线程中调用closeWorker 方法。
为什么要使用invokeMethod，而不是把一个信号连接到槽然后发出这个信号？

标签： c++ multithreading qt signals slot

【解决方案1】：

尝试发布自定义事件，而不是直接调用方法。这将要求您在处理您的自定义事件的目标上实现一个事件过滤器。只要目标线程中的事件循环处于活动状态，事件发布就始终有效。

也看看这个答案here。还有here。希望这会有所帮助。

【讨论】：

你为什么要使用更复杂的方法来做同样的事情？