C++ GUI QT 第4版 之线程（一） 线程的创建

setLayout(mainLayout); 设计完格式之后 最后要加这一句

线程的东西
首先要定义一个线程，之后才可以利用它
Threaad A；
常用函数：
.isRunning（）如果线程正在运行，则返回true;否则返回false。
.Start()  开始调用线程的run（）函数执行这个线程。 执行完run()函数后，线程结束
所有的费时的工作都在线程中完成，在主进程中只是开启和关闭线程
.wait()函数 等待线程结束的函数
与此QThread中对象关联的线程完成执行（即当它从运行返回（））。如果线程完成此功能将返回true。如果线程尚未启动，但它也返回true。

threads.pro

QT       += core gui

greaterThan(QT_MAJOR_VERSION, 4): QT += widgets

TEMPLATE      = app

CONFIG       += console thread

HEADERS       = thread.h \

                threaddialog.h

SOURCES       = main.cpp \

                thread.cpp \

                threaddialog.cpp

OTHER_FILES +=

thread.h   线程的定义，线程中最主要的函数是run()和stop()函数，run()函数是线程启动之后要执行的函数，而线程的终止要用stop()函数

#ifndef THREAD_H
#define THREAD_H
#include <QThread>
#include <QPushButton>
#include <QLayout>
class Thread : public QThread
{
    Q_OBJECT
public:
    Thread();
    void setMessage(const QString &message);
    void stop();
protected:
    void run();
private:
    QString messageStr;
    volatile bool stopped;  //函数终止的标志位  必须是volatile类型 
};
#endif

thread.cpp

#include <QtCore>
#include <iostream>
#include "thread.h"
Thread::Thread()
{
    stopped = false;//设置为false
}
void Thread::setMessage(const QString &message)
{
    messageStr = message;
}
void Thread::run()
{
    while (!stopped)
        std::cerr << qPrintable(messageStr);
    stopped = false;
    std::cerr << std::endl;
}
void Thread::stop()  //用stopped标识符来终止进程
{
    stopped = true;
}
threaddialog.h  //主程序函数  在这里面  启动和终止线程
#ifndef THREADDIALOG_H
#define THREADDIALOG_H
#include <QDialog>
#include "thread.h"
class Threaddialog:public QDialog
{
   Q_OBJECT
public:
    Threaddialog(QWidget *parent=0);
protected:
    void closeEvent(QCloseEvent *event);  //回收资源
private slots:
    void  startOrStopThreadA();
    void  startOrStopThreadB();
private:
    Thread threadA;
    Thread threadB;
    QPushButton *threadAButton;
    QPushButton *threadBButton;
    QPushButton *quitButton;
};
#endif // THREADDIALOG_H
threaddialog.cpp 
#include <QtGui>
#include "threaddialog.h"
Threaddialog::Threaddialog(QWidget *parent):QDialog(parent)
{
   threadA.setMessage("A");
   threadB.setMessage("B");
   threadAButton=new QPushButton(tr("Start A"));
   threadBButton=new QPushButton(tr("Start B"));
   quitButton=new QPushButton(tr("Quit"));
   quitButton->setDefault(true);
    connect(threadAButton,SIGNAL(clicked()),this,SLOT(startOrStopThreadA()));
    connect(threadBButton,SIGNAL(clicked()),this,SLOT(startOrStopThreadB()));
    connect(quitButton,SIGNAL(clicked()),this,SLOT(close()));
   QHBoxLayout *mainLayout= new QHBoxLayout;
   mainLayout->addWidget(threadAButton);
   mainLayout->addWidget(threadBButton);
   mainLayout->addWidget(quitButton);
   setLayout(mainLayout);
}
void Threaddialog::startOrStopThreadA()
{
    if(threadA.isRunning())
     {
         threadA.stop();  //终止线程
         threadAButton->setText(tr("Start A"));
    }
    else
     {
        threadA.start();  //启动线程，线程会去执行其中的run()函数
        threadAButton->setText(tr("Stop A"));
    }
}
void Threaddialog::startOrStopThreadB()
{
   if(threadB.isRunning())
      {
         threadB.stop();
         threadBButton->setText(tr("Start B"));
      }
   else
     {
        threadB.start();
        threadBButton->setText(tr("stop B"));
     }
}
void Threaddialog::closeEvent(QCloseEvent *event)  //回收资源
{
  threadA.stop();
  threadB.stop();
  threadA.wait();
  threadB.wait();
  event->accept();
}

main.cpp

#include <QApplication>
#include "threaddialog.h"
int main(int argc, char *argv[])
{
    QApplication app(argc, argv);
    ThreadDialog dialog;
    dialog.show();
    return app.exec();
}