Qt实现多线程编程的两种方式

朱雀 2022-12-13 11:25 248阅读 0赞

# Qt实现多线程编程的两种方式 #

--------------------

**方式一：** 继承自QThread类，覆写run函数。此实现方法只有run函数内的代码是运行在子线程内。

代码示例：

#ifndef QDEMOTHREAD_H
    #define QDEMOTHREAD_H
    
    #include <QThread>
    #include <QDebug>
    
    class QDemoThread : public QThread
    { 
        Q_OBJECT
    
    public:
        QDemoThread(QObject* parent = nullptr);
        ~QDemoThread();
    
    protected:
        void run() override;
    
    public:
        void stop();
    
    private:
        bool flag;
    };
    
    #endif // QDEMOTHREAD_H

#include "qdemothread.h"
    
    QDemoThread::QDemoThread(QObject* parent) : QThread(parent)
    { 
    
    }
    
    QDemoThread::~QDemoThread()
    { 
    
    }
    
    void QDemoThread::run()
    { 
        flag = true;
        while(flag)
        { 
            qDebug() << "thread id:" << QThread::currentThreadId();
            sleep(1);
        }
    }
    
    void QDemoThread::stop()
    { 
        flag = false;
        if(isRunning())
        { 
            exit();  // 结束线程
            wait();  // 等待退出
        }
    }

#include "widget.h"
    #include "ui_widget.h"
    
    Widget::Widget(QWidget *parent) :
        QWidget(parent),
        ui(new Ui::Widget)
    { 
        ui->setupUi(this);
    
        demoThread = new QDemoThread(this);
    
        qDebug() << "main thread id:" << QThread::currentThreadId();
    }
    
    Widget::~Widget()
    { 
        demoThread->stop();  // 退出线程
        delete ui;
    }
    
    void Widget::on_pushButton_clicked()
    { 
        if(!demoThread->isRunning())
        { 
            demoThread->start();  // 启动线程
        }
    }

**运行效果：**  
![在这里插入图片描述][20201011105916608.png_pic_center]

--------------------

**方式二：** 创建一个QThread和QWorker(继承自QObject)类对象，使用moveToThread函数移动到thread中运行，通过thread类start信号和worker槽函数绑定

**示例代码：**

**QWorker类：**

#ifndef QWORKER_H
    #define QWORKER_H
    
    #include <QObject>
    #include <QThread>
    #include <QDebug>
    
    class QWorker : public QObject
    { 
        Q_OBJECT
    public:
        explicit QWorker(QObject *parent = nullptr);
    
    signals:
    
    public slots:
        void doWork();
    };
    
    #endif // QWORKER_H

#include "qworker.h"
    
    QWorker::QWorker(QObject *parent) : QObject(parent)
    { 
    
    }
    
    void QWorker::doWork()
    { 
        qDebug() << "thread id:" << QThread::currentThreadId();
    }

**主线程：**

#include "mainwindow.h"
    #include "ui_mainwindow.h"
    
    MainWindow::MainWindow(QWidget *parent) :
        QMainWindow(parent),
        ui(new Ui::MainWindow)
    { 
        ui->setupUi(this);
    
        qDebug() << "main thread id:" << QThread::currentThreadId();
    }
    
    MainWindow::~MainWindow()
    { 
        delete ui;
    }
    
    void MainWindow::on_pushButton_clicked()
    { 
        QThread* thread = new QThread();
        QWorker* worker = new QWorker();
        QObject::connect(thread, SIGNAL(started()), worker, SLOT(doWork()));
        QObject::connect(thread, SIGNAL(finished()), worker, SLOT(deleteLater()));
        QObject::connect(thread, SIGNAL(finished()), thread, SLOT(deleteLater()));
        worker->moveToThread(thread);
        thread->start();
    }

**运行效果：**  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxMTUzNDcxNTAz_size_16_color_FFFFFF_t_70_pic_center]

--------------------

ends…

[20201011105916608.png_pic_center]: /images/20221123/29321605aaec4d91a1b23fd5ec658656.png
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxMTUzNDcxNTAz_size_16_color_FFFFFF_t_70_pic_center]: /images/20221123/a52926e4ea8c4aff8fce4bcaefb67f24.png