Qt5多线程＜12＞

1.多线程的简单实现

        <1> 在头文件threaddlg.h声明用于界面显示所需的控件，其代码如下：

#ifndef THREADDLG_H
#define THREADDLG_H#include <QDialog>
#include <QPushButton>
#include "workthread.h"
#define MAXSIZE 5class ThreadDlg : public QDialog
{Q_OBJECTpublic:ThreadDlg(QWidget *parent = 0);~ThreadDlg();    
private:QPushButton *startBtn;QPushButton *stopBtn;QPushButton *quitBtn;
public slots:void slotStart();void slotStop();
private:WorkThread *workThread[MAXSIZE];
};#endif // THREADDLG_H

         <2> 在源文件“threaddlg.cpp的构造函数中，完成各个控件的初始化工作其具体代码如下:

#include "threaddlg.h"
#include <QHBoxLayout>ThreadDlg::ThreadDlg(QWidget *parent): QDialog(parent)
{setWindowTitle(tr("线程"));startBtn = new QPushButton(tr("开始"));stopBtn = new QPushButton(tr("停止"));quitBtn = new QPushButton(tr("退出"));QHBoxLayout *mainLayout = new QHBoxLayout(this);mainLayout->addWidget(startBtn);mainLayout->addWidget(stopBtn);mainLayout->addWidget(quitBtn);connect(startBtn,SIGNAL(clicked()),this,SLOT(slotStart()));connect(stopBtn,SIGNAL(clicked()),this,SLOT(slotStop()));connect(quitBtn,SIGNAL(clicked()),this,SLOT(close()));
}ThreadDlg::~ThreadDlg()
{}void ThreadDlg::slotStart()
{for(int i=0;i<MAXSIZE;i++){workThread[i]=new WorkThread();}for(int i=0;i<MAXSIZE;i++){workThread[i]->start();}startBtn->setEnabled(false);stopBtn->setEnabled(true);
}void ThreadDlg::slotStop()
{for(int i=0;i<MAXSIZE;i++){workThread[i]->terminate();workThread[i]->wait();}startBtn->setEnabled(true);stopBtn->setEnabled(false);
}

        <3> 以上完成了界面的设计及调用线程实例，下面的内容是具体的功能实现。

        <3-1>在头文件“workthread.h”中，工作线程WorkThread类继承自QThreao类。重新实现run()函数。其具体代码如下:

#ifndef WORKTHREAD_H
#define WORKTHREAD_H#include <QThread>class WorkThread : public QThread
{Q_OBJECT
public:WorkThread();
protected:void run();
};#endif // WORKTHREAD_H

        <3-2> 在源文件“workthread.cpp”中添加具体实现代码如下:

#include "workthread.h"
#include <QtDebug>WorkThread::WorkThread()
{
}void WorkThread::run()
{while(true){for(int n=0;n<10;n++)qDebug()<<n<<n<<n<<n<<n<<n<<n<<n;}
}

<4> main.cpp中代码实现

#include "threaddlg.h"
#include <QApplication>int main(int argc, char *argv[])
{QApplication a(argc, argv);ThreadDlg w;w.show();return a.exec();
}

<5> 运行效果，如下所示：

2.多线程的控制

        多线程控制可通过互斥量和信号量。

2.1 互斥量

       为了防止多个线程对同一个资源进行访问，Qt中加入互斥量，互斥量可以通过QMutex或者QMutexLocker