QT中的多线程编程

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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）

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