QT多线程的两种创建方法

柔光的暖阳◎ 2022-02-27 18:14 445阅读 0赞

Qt有两种多线程的方法，其中一种是继承QThread的run函数，另外一种是把一个继承于QObject的类转移到一个Thread里。  
Qt4.8之前都是使用继承QThread的run这种方法，但是Qt4.8之后，Qt官方建议使用第二种方法。两种方法用起来都比较方便，但继承QObject的方法更加灵活。这里要记录的是如何正确的创建一个线程。

值得注意的是第一种方法只有run()里面在新的线程里，第二种方法就可以在新线程中调用函数  
下一个博客讲怎么用互斥锁进行线程同步  
//mainwindow.cpp

#include "mainwindow.h"
    #include "ui_mainwindow.h"
    
    extern int globalCount ;
    
    MainWindow::MainWindow(QWidget *parent) :
        QMainWindow(parent),
        ui(new Ui::MainWindow)
    {
        ui->setupUi(this);
        qDebug()<<tr("主线程id:")<<QThread::currentThreadId();
        
        //多线程方式1
        myThread = new MyThread();//继承QThread
        myThread->start();
    
        //多线程方式2
        myThread1 = new MyThread1();//继承QObject
        thread1 = new QThread;
        connect(thread1, SIGNAL(started()),myThread1, SLOT(doWork()));//个人推荐这种
        myThread1->moveToThread(thread1);
        thread1->start();
    
    }
    
    MainWindow::~MainWindow()
    {
        delete ui;
    }

//mainwindow.h

#ifndef MAINWINDOW_H
    #define MAINWINDOW_H
    
    #include <QMainWindow>
    #include "mythread.h"
    #include <QThread>
    #include <QObject>
    #include <QTimer>
    #include "mythread1.h"
    
    namespace Ui {
    class MainWindow;
    }
    
    class MainWindow : public QMainWindow
    {
        Q_OBJECT
    
    public:
        explicit MainWindow(QWidget *parent = 0);
        ~MainWindow();
    
    private slots:
    
    private:
        Ui::MainWindow *ui;
        MyThread *myThread;
        MyThread1 *myThread1;
        QThread *thread1 ;
    };
    
    #endif // MAINWINDOW_H

//方式1：只有run函数内的属于新的线程  
//MyThread.cpp

#include "mythread.h"
    
    extern int globalCount ;
    
    MyThread::MyThread()
    {
        isStop = true;
    }
    
    void MyThread::closeThread()
    {
        isStop = true;
    }
    
    void MyThread::run()//只有run()里面在新的线程里
    {
    
    
        qDebug()<<tr("mythread QThread::currentThreadId()==")<<QThread::currentThreadId();
        isStop = false;
    
    //这种方式还是相当于在主线程里面执行
    //    timer= new QTimer(NULL);
    //    connect(timer, SIGNAL(timeout()), this, SLOT(onTimeout()));
    //    timer->start(1000);
    //    this->exec();
        while(1)
        {
            if(isStop)
            {
                return;
            }
            qDebug()<<"globalCount: " << ++globalCount <<QThread::currentThreadId();
    
            sleep(1);//QThread
        }
    }
    
    //这种方式还是相当于在主线程里面执行
    void MyThread::onTimeout()
    {
        qDebug()<<tr("mythread QThread::currentThreadId()==")<<QThread::currentThreadId();
        qDebug()<<"globalCount: " << ++globalCount;
    
    }

//MyThread.h

#ifndef MYTHREAD_H
    #define MYTHREAD_H
    
    #include <QObject>
    #include <QThread>
    #include <QDebug>
    #include <QTimer>
    
    class MyThread : public QThread
    {
        Q_OBJECT
    public:
        explicit MyThread();
        void run();//重写基类的run函数
        void closeThread();
    
    signals:
    
    public slots:
        void onTimeout();
    private:
        QTimer * timer;
        bool isStop = true;
    };
    
    #endif // MYTHREAD_H

//MyThread1.cpp

#include "mythread1.h"
    #include <QMutex>
    
    extern QMutex mutex;
    QMutex mutex1;
    extern int globalCount ;
    
    MyThread1::MyThread1(QObject *parent) : QObject(parent)
    {
        isStop = true;
    }
    
    void MyThread1::closeThread()
    {
        isStop = true;
    }
    
    void MyThread1::doWork()
    {
        qDebug()<<tr("mythread2 QThread::currentThreadId()==")<<QThread::currentThreadId();
        isStop = false;
    
        //定时方式1:(都是在子线程中)
        timer= new QTimer(this);
        connect(timer, SIGNAL(timeout()), this, SLOT(onTimeout()));
        timer->start(1000);
    
        //定时方式2:(都是在子线程中)
    //    while(1)
    //    {
    //        if(isStop)
    //        {
    //            return;
    //        }
    
    //        QMutexLocker locker(&mutex);
    //        qDebug()<<"globalCount: " << ++globalCount <<QThread::currentThreadId();
    
    //        Sleep(1000);//<windows.h>,大写的S,单位是微秒
    //    }
    }
    
    void MyThread1::onTimeout()
    {
        QMutexLocker locker(&mutex1);
        qDebug()<<"globalCount: " << ++globalCount <<QThread::currentThreadId();
    
    }

//MyThread1.h

#ifndef MYTHREAD1_H
    #define MYTHREAD1_H
    
    #include <QObject>
    #include <QThread>
    #include <QDebug>
    #include <QTimer>
    #include <windows.h>//Sleep(1);大写的S
    
    
    
    class MyThread1 : public QObject
    {
        Q_OBJECT
    public:
        explicit MyThread1(QObject *parent = 0);
        void closeThread();
    signals:
    
    public slots:
        void doWork();
        void onTimeout();
    private:
        QTimer * timer;
        bool isStop = true;
    };
    
    #endif // MYTHREAD1_H