Qt5.9继承QObject创建多线程实例_C/C++

本博客主要总结Qt中创建多线程的另一种方法，不是通过继承类QThread，而是通过继承对象QObject，来实现多线程。（可以直接跳过下面内容，看1.1内容）

利用继承QObject方法创建多线程，主要的步骤有一下几点：（注意：退出线程循环后，还要调用QThread::quit()函数，该线程才会触发QThread::finished()信号）

a1：首先创建一个类MyThread，基类为QObject。

a2：在类MyThread中创建一个槽函数，用于运行多线程里面的代码。所有耗时代码，全部在这个槽函数里面运行。

a3：实例一个QThread线程对象（容器），将类MyThread的实例对象转到该容器中，用函数void QObject::moveToThread(QThread *thread);

myObjectThread->moveToThread(firstThread);

a4：用一个信号触发该多线程槽函数，比如用QThread::started()信号。

connect(firstThread,SIGNAL(started()),myObjectThread,SLOT(startThreadSlot()));

a5：用信号QThread::finished绑定槽函数QThread::deleteLatater()，在线程退出时，销毁该线程和相关资源。

connect(firstThread,SIGNAL(finished()),firstThread,SLOT(deleteLater()));

a6：所有线程初始化完成后，启动函数QThread::start()开启多线程，然后自动触发多线程启动信号QThread::started()。

具体的教程如下图所示：

1.1新建一个widget工程，不要勾选ui界面。然后分别在mythread.h，mythread.cpp，widget.h，widget.cpp，main.cpp分别添加如下代码。

mythread.h

#ifndef MYTHREAD_H
#define MYTHREAD_H
 
#include <QObject>
 
class MyThread : public QObject
{
    Q_OBJECT
public:
    explicit MyThread(QObject *parent = nullptr);
 
    void closeThread();
 
signals:
 
public slots:
    void startThreadSlot();
 
private:
    volatile bool isStop;
};
 
#endif // MYTHREAD_H

mythread.cpp

#include "mythread.h"
#include <QDebug>
#include <QThread>
 
MyThread::MyThread(QObject *parent) : QObject(parent)
{
    isStop = false;
}
 
void MyThread::closeThread()
{
    isStop = true;
}
 
void MyThread::startThreadSlot()
{
    while (1)
    {
        if(isStop)
            return;
        qDebug()<<"MyThread::startThreadSlot QThread::currentThreadId()=="<<QThread::currentThreadId();
        QThread::sleep(1);
    }
}

widget.h

#ifndef WIDGET_H
#define WIDGET_H
 
#include <QWidget>
#include <QVBoxLayout>
#include <QPushButton>
#include <QThread>
#include "mythread.h"
 
class Widget : public QWidget
{
    Q_OBJECT
 
public:
    Widget(QWidget *parent = 0);
    ~Widget();
 
    void createView();
 
private slots:
    void openThreadSlot();
    void closeThreadSlot();
    void finishedThreadSlot();
 
private:
    QVBoxLayout *mainLayout;
    QThread *firstThread;
    MyThread *myObjectThread;
};
 
#endif // WIDGET_H

widget.cpp

#include <QDebug>
#include "widget.h"
 
Widget::Widget(QWidget *parent)
    : QWidget(parent)
{
    createView();
}
 
Widget::~Widget()
{
}
 
void Widget::createView()
{
    /*UI界面*/
    mainLayout = new QVBoxLayout(this);
    QPushButton *openThreadBtn = new QPushButton(tr("打开线程"));
    QPushButton *closeThreadBtn = new QPushButton(tr("关闭线程"));
    mainLayout->addWidget(openThreadBtn);
    mainLayout->addWidget(closeThreadBtn);
    mainLayout->addStretch();
    connect(openThreadBtn,SIGNAL(clicked(bool)),this,SLOT(openThreadSlot()));
    connect(closeThreadBtn,SIGNAL(clicked(bool)),this,SLOT(closeThreadSlot()));
}
 
void Widget::openThreadSlot()
{
    /*开启一条多线程*/
    qDebug()<<tr("开启线程");
    firstThread = new QThread;                                                      //线程容器
    myObjectThread = new MyThread;
    myObjectThread->moveToThread(firstThread);                                      //将创建的对象移到线程容器中
    connect(firstThread,SIGNAL(finished()),myObjectThread,SLOT(deleteLater()));        //终止线程时要调用deleteLater槽函数
    connect(firstThread,SIGNAL(started()),myObjectThread,SLOT(startThreadSlot()));  //开启线程槽函数
    connect(firstThread,SIGNAL(finished()),this,SLOT(finishedThreadSlot()));
    firstThread->start();                                                           //开启多线程槽函数
    qDebug()<<"mainWidget QThread::currentThreadId()=="<<QThread::currentThreadId();
}
 
void Widget::closeThreadSlot()
{        
    qDebug()<<tr("关闭线程");
    if(firstThread->isRunning())
    {
        myObjectThread->closeThread();  //关闭线程槽函数
        firstThread->quit();            //退出事件循环
        firstThread->wait();            //释放线程槽函数资源
    }
}
 
void Widget::finishedThreadSlot()
{
    qDebug()<<tr("多线程触发了finished信号123");
}

main.cpp

#include "widget.h"
#include <QApplication>
 
int main(int argc, char *argv[])
{
    QApplication a(argc, argv);
    Widget w;
    w.resize(960,640);
    w.show();
 
    return a.exec();
}

1.2程序构建和运行后，结果如下图所示：

Qt5.9继承QObject创建多线程实例