c++ - 在 Qt 的子线程中调用函数？

Question

我有一个在不同时间调用子线程函数的主线程，但我不确定这是否是在 Qt 中执行此操作的正确方法。下面的代码有什么问题并寻找更好的替代方法

当主线程释放锁时，主线程会无限运行，子进程会做一些工作。

#include <QtCore/QCoreApplication>
#include <QSemaphore>
#include <QThread> 
QSemaphore sem(0);
class Background : public QThread 
{
protected:
void run() 
{ 
for(;;)
{ 
   sem.acquire(1); 
   qDebug("Child function ran");
} 
} 
};

int main(int argc, char *argv[])  
{   
QCoreApplication a(argc, argv);   
Background child; 
child.start();
qDebug("Main running"); 
qDebug("release a lock");
sem.release(1);
qDebug("Do somework in main");   
//call child
sem.release(1);
sem.release(1);
return a.exec();  
}

Answer 1

编辑:整篇文章的返工以涵盖基础知识。

Background.h:

#ifndef BACKGROUND_H
#define BACKGROUND_H

#include <QThread>
#include <QObject>

class Background : public QThread 
{
Q_OBJECT
public:
   Background(QObject* parent = 0):QThread(parent){}
protected:
   void run()
   {
      qDebug(qPrintable(QString("Child function ran in thread: %1").arg(QThread::currentThreadId())));
   }
};

class BackgroundConcurrent : public QObject
{
Q_OBJECT
public:
   BackgroundConcurrent(QObject* parent = 0):QObject(parent){}
public slots:
   void doWork() const
   {
      qDebug(qPrintable(QString("Concurrent child function ran in thread: %1").arg(QThread::currentThreadId())));
   }
};

class BackgroundTrigger : public QObject
{
Q_OBJECT
public:
   BackgroundTrigger(QObject* parent = 0):QObject(parent){}
   ~BackgroundTrigger()
   {
      foreach(QObject* child, children())
      {
         QThread* childThread = qobject_cast<QThread*>(child);
         if (childThread)
            childThread->wait();
      }
   }
public slots:
   void triggerWorker()
   {
      Background* child = new Background(this);
      child->start();
   }
};

#endif // BACKGROUND_H

main.cpp:

#include "Background.h"

#include <QCoreApplication>
#include <QtConcurrentRun>

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

// Using QThread
BackgroundTrigger childTrigger;
qDebug(qPrintable(QString("Main function ran in thread: %1").arg(QThread::currentThreadId())));

// Call child
childTrigger.triggerWorker();
childTrigger.triggerWorker();

// Using QtConcurrent
BackgroundConcurrent cchild;
QFuture<void> future1 = QtConcurrent::run(&cchild, &BackgroundConcurrent::doWork);
QFuture<void> future2 = QtConcurrent::run(&cchild, &BackgroundConcurrent::doWork);

return 0;
}

示例输出:

Main function ran in thread: 1087038064Child function ran in thread: 1091267472Child function ran in thread: 1093417872Concurrent child function ran in thread: 1095519120Concurrent child function ran in thread: 1097644944

Be sure you run moc on your header files, qmake and cmake both support creating your makefiles.

Here is the CMakeLists.txt file I used to build the code:

cmake_minimum_required(VERSION 2.6)

#Project name
project(TEST)

#Use Qt4
find_package(Qt4)

if(QT4_FOUND)
set(QT_USE_QTOPENGL TRUE)
include(${QT_USE_FILE})

set(LIBS
    ${QT_LIBRARIES}
    )

#Source files (*.cpp, *.o)
set(TEST_SRCS main.cpp)

#Header files (*.h[pp])
set(TEST_HDRS Background.h)

#Qt macros to handle uic, moc, etc...
QT4_WRAP_CPP(TEST_MOC ${TEST_HDRS} OPTIONS -nw)

set(TEST_ALLSRC ${TEST_SRCS} ${TEST_MOC})

#Create main
add_executable(test ${TEST_ALLSRC})
target_link_libraries(test ${LIBS})

endif(QT4_FOUND)