QT多线程创建的误区：run函数

╰+攻爆jí腚メ 2022-02-26 20:16 357阅读 0赞

直接上代码吧，注意这种方法创建的多线程，**只有run函数内的属于新的线程**，OnTempTimer()虽然是run函数调用的，但是是主线程在执行，一定要注意啊。这样弄相当于没有任何意义，还是主线程在处理函数。  
下一个博客有讲怎么实现多线程的正确创建和使用

MainWindow.cpp

MysqlThread = new ReconnectMysql();
        MysqlThread->start();

reconnectmysql.cpp

#include "reconnectmysql.h"
    
    ReconnectMysql::ReconnectMysql()
    {
    
    }
    
    void ReconnectMysql::run()
    {
        qDebug()<< "run()";
    
        //Timer = new QTimer(this);这样写会报错：
        //Parent is ReconnectMysql(0xd621978), parent's thread is QThread(0x4ac5dd0),
        //current thread is ReconnectMysql(0xd621978)
    
        Timer = new QTimer();//或者Timer = new QTimer(NULL);
        //这句话也要在run()不能像这样给定时器指定父对象 Timer = new QTimer(this);
        Timer->start(1000);
        connect(Timer, SIGNAL(timeout()), this, SLOT(OnTempTimer()));
        this->exec();//不加这句话定时器不执行
    }
    
    void ReconnectMysql::OnTempTimer()
    {
        qDebug()<< "OnTempTimer()";
    }

reconnectmysql.h 注意继承的QThread

#ifndef RECONNECTMYSQL_H
    #define RECONNECTMYSQL_H
    
    #include <QObject>
    #include <QThread>
    #include <QTimer>
    #include <QDebug>
    
    class ReconnectMysql : public QThread
    {
        Q_OBJECT
    public:
        explicit ReconnectMysql();
        void run();
    
    signals:
    
    public slots:
        void OnTempTimer();
    private:
        QTimer *Timer;
    
    };
    
    #endif // RECONNECTMYSQL_H

打印：  
![在这里插入图片描述][20190327173528245.png]

怎么验证以上的说法呢，很简单，用这个函数QThread::currentThreadId();获取当前线程的ID

qDebug()<<tr("主线程id:")<<QThread::currentThreadId();
       
        //多线程方式1
        myThread = new MyThread();
        myThread->start();

void MyThread::run()//只有run()里面在新的线程里
    {
        qDebug()<<tr("mythread QThread::currentThreadId()==")<<QThread::currentThreadId();
    
    //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();
        }

//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;
    
    }

![在这里插入图片描述][2019032810325192.png]

[20190327173528245.png]: /images/20220227/ac6e30f81d0a4c79b4a342edd5eb789d.png
[2019032810325192.png]: /images/20220227/43758519c8d1470895688b6e7a3e5d46.png