Qt 多线程实现

本例子实现生成两个线程，向屏幕输出消息。

Qt创建ThreadDialog，编辑threaddialog.h和threaddialog.cpp

threaddialog.h代码实现：

#ifndef THREADDIALOG_H
#define THREADDIALOG_H

#include <QDialog>
#include <QtWidgets>
#include "thread.h"
//导入自定义类

namespace Ui {
class ThreadDialog;
}

class ThreadDialog : public QDialog
{
    Q_OBJECT

public:
    explicit ThreadDialog(QWidget *parent = 0);
    ~ThreadDialog();

protected:
    void closeEvent(QCloseEvent *);//设置关闭事件

private:
    Ui::ThreadDialog *ui;
    //定义两个线程，其中Thread是自定义类
    Thread threadA;
    Thread threadB;

private slots:
    //三个按钮对应的消息槽
    void starOrStopThreadA();
    void starOrStopThreadB();
    //void quitSlot();
};

#endif // THREADDIALOG_H

threaddialog.cpp代码实现：

#include "threaddialog.h"
#include "ui_threaddialog.h"

ThreadDialog::ThreadDialog(QWidget *parent) :
    QDialog(parent),
    ui(new Ui::ThreadDialog)
{
    ui->setupUi(this);

    QObject::connect(ui->threadAButton,SIGNAL(clicked(bool)),this,SLOT(starOrStopThreadA()));
    QObject::connect(ui->threadBButton,SIGNAL(clicked(bool)),this,SLOT(starOrStopThreadB()));
    //QObject::connect(ui->quitButton,SIGNAL(clicked(bool)),this,SLOT(close()));

    threadA.setMessage("A");
    threadB.setMessage("B");
}

ThreadDialog::~ThreadDialog()
{
    delete ui;
}

void ThreadDialog::closeEvent(QCloseEvent *event)
{
    threadA.stop();
    threadB.stop();

    threadA.wait();
    threadB.wait();

    event->accept();
}

void ThreadDialog::starOrStopThreadA()
{
    if(threadA.isRunning())
        //当再次点击ButtonA时，启动stop()
    {
        threadA.stop();
        ui->threadAButton->setText("start A");
    }
    else//当点击开始ButtonA时，如果A没有运行，则启动A线程
    {
        threadA.start();
        ui->threadAButton->setText("stop A");
    }
}

void ThreadDialog::starOrStopThreadB()
{
    if(threadB.isRunning())
    {
        threadB.stop();
        ui->threadBButton->setText("start B");
    }
    else
    {
        threadB.start();
        ui->threadBButton->setText("stop B");
    }
}

自定义类thread.h代码实现：

#ifndef THREAD_H
#define THREAD_H

#include <QThread>
#include <QtDebug>

class Thread : public QThread
{
public:
    Thread();
    void setMessage(const QString &message);
    void stop();
    //已从QThread中继承得到start()方法

protected:
    void run();

private:
    QString messageStr;//输出的信息
    volatile bool stopped;//控制线程的开关
};

#endif // THREAD_H

thread.cpp代码实现：

#include "thread.h"
#include <iostream>
using namespace std;

Thread::Thread()
{
    stopped = false;//初始线程是开始的
}

void Thread::setMessage(const QString &message)
{
    messageStr = message;
}

void Thread::run()
//启动A线程之后，先屏幕不断得输出消息，知道stopped变成true
{
    while(!stopped)
    {
        cerr <<messageStr.toStdString();//将设置的字符串信息设置输出到debug
        sleep(1);
    }
    stopped = false;
    //将stopped设置false，便于另一个线程继续执行
}

void Thread::stop()
//将stopped设置true，即停止线程
{
    stopped = true;
}

Ui如图所示：