QT中的多线程编程

QT为多线程编程提供了很多类，其中最重要的就是QThread了，在QT中定义的任何线程都是他的派生类。最重要的就是重写run()函数，因为类的主要功能就是在run中实现，实现的方法是调用start函数，start函数就会自动调用run函数。

以下程序是一个简单的多线程程序，主要功能是生成两个线程，每个线程不停的打印自己的相关信息。

代码如下：

form1.h

/****************************************************************************

** Form interface generated from reading ui file 'form1.ui'

**

** Created: 日 2月 10 14:45:53 2008

** by: The User Interface Compiler ($Id: qt/main.cpp 3.1.1 edited Nov 21 17:40 $)

**

** WARNING! All changes made in this file will be lost!

****************************************************************************/

#ifndef FORM1_H

#define FORM1_H

#include <qvariant.h>

#include <qwidget.h>

#include <qthread.h>

#include <qmutex.h>

#include <iostream.h>

class QVBoxLayout;

class QHBoxLayout;

class QGridLayout;

class QPushButton;

class MutthreadA : public QThread

{

//QT_THREAD_SUPPORT

public:

void run()

{

while(1)

{

cout << "THE THREAD AZD IS RUN/n";

sleep(2);

}

};

};

class MutthreadB:public QThread

{

public:

void run()

{

while(1)

{

cout << "THE THREAD B IS RUN/n";

sleep(2);

}

};

};

class Form1 : public QWidget

{

Q_OBJECT

public:

Form1( QWidget* parent = 0, const char* name = 0, WFlags fl = 0 );

~Form1();

QPushButton* pushButton1;

QPushButton* pushButton2;

MutthreadA AA;

MutthreadB BB;

QMutex mutex;

protected:

protected slots:

virtual void languageChange();

virtual void Ta();

virtual void Tb();

};

#endif // FORM1_H

form1.cpp

/****************************************************************************

** Form implementation generated from reading ui file 'form1.ui'

**

** Created: 日 2月 10 14:46:03 2008

** by: The User Interface Compiler ($Id: qt/main.cpp 3.1.1 edited Nov 21 17:40 $)

**

** WARNING! All changes made in this file will be lost!

****************************************************************************/

#include "form1.h"

#include <qvariant.h>

#include <qpushbutton.h>

#include <qlayout.h>

#include <qtooltip.h>

#include <qwhatsthis.h>

#include <qimage.h>

#include <qpixmap.h>

#include <qmutex.h>

/*

* Constructs a Form1 as a child of 'parent', with the

* name 'name' and widget flags set to 'f'.

*/

Form1::Form1( QWidget* parent, const char* name, WFlags fl )

: QWidget( parent, name, fl )

{

if ( !name )

setName( "Form1" );

pushButton1 = new QPushButton( this, "pushButton1" );

pushButton1->setGeometry( QRect( 50, 80, 161, 61 ) );

pushButton2 = new QPushButton( this, "pushButton2" );

pushButton2->setGeometry( QRect( 50, 200, 161, 61 ) );

languageChange();

resize( QSize(600, 480).expandedTo(minimumSizeHint()) );

connect(pushButton1,SIGNAL(clicked()),this,SLOT(Ta()));

connect(pushButton2,SIGNAL(clicked()),this,SLOT(Tb()));

}

/*

* Destroys the object and frees any allocated resources

*/

Form1::~Form1()

{

// no need to delete child widgets, Qt does it all for us

}

/*

* Sets the strings of the subwidgets using the current

* language.

*/

void Form1::languageChange()

{

setCaption( tr( "Form1" ) );

pushButton1->setText( tr( "printerA" ) );

pushButton2->setText( tr( "printerB" ) );

}

void Form1::Ta()

{

if(AA.running())

{

AA.wait();

mutex.unlock();

}

else

{

mutex.lock();

//AA.run();

AA.start();

}

}

void Form1::Tb()

{

if(BB.running())

{

BB.wait();

mutex.unlock();

}

else

{

mutex.lock();

// BB.run();

BB.start();

}

}

main.cpp

#include <qapplication.h>

#include "form1.h"

int main( int argc, char ** argv )

{

QApplication a( argc, argv );

Form1 w;

w.show();

a.connect( &a, SIGNAL( lastWindowClosed() ), &a, SLOT( quit() ) );

return a.exec();

}

程序中用了互斥量mutex，其实现了两个线程间的通信。还需要注意的是当调用线程的start函数时，run函数会自动被调用。但是需要注意的是也可以直接调用run函数来实现线程的相关功能，但是这样将不会出现多线程，系统还是执行的单线程，即使先执行AA线程，AA线程执行完了后才执行BB线程。

程序执行结果如下：

THE THREAD AZD IS RUN

THE THREAD B IS RUN

THE THREAD AZD IS RUN

THE THREAD B IS RUN

THE THREAD AZD IS RUN

THE THREAD B IS RUN

THE THREAD AZD IS RUN

THE THREAD B IS RUN

THE THREAD AZD IS RUN

THE THREAD B IS RUN

THE THREAD AZD IS RUN

THE THREAD B IS RUN

THE THREAD AZD IS RUN

THE THREAD B IS RUN

.

.

.

.

.

还需要注意的一点是在编译的时候必须在makefile中加入-DQT_THREAD_SUPPORT即：

CFLAGS = -pipe -Wall -W -O2 -march=i386 -mcpu=i686 -g -DGLX_GLXEXT_LEGACY -fno-use-cxa-atexit -fno-exceptions -DQT_NO_DEBUG -DQT_THREAD_SUPPORT

CXXFLAGS = -pipe -Wall -W -O2 -march=i386 -mcpu=i686 -g -DGLX_GLXEXT_LEGACY -fno-use-cxa-atexit -fno-exceptions -DQT_NO_DEBUG -DQT_THREAD_SUPPORT

以实现对多线程的支持。（前提是QT在编译的时候已经加入了多线程选项,即生成了多线程库）