QT 创建线程的三种方法

方式一：派生于QThread

  派生于QThread,这是Qt创建线程中最常用的方法，重写void QThread::run(),在run写具体的内容，外部通过start调用，即可执行线程体run();

注意：

派生于QThread的类，构造函数属于主线程，run函数属于子线程，可以通过打印线程id判断。

方式二：派生于QRunable

派生于QRunable，重写run()方法里处理其他任务，调用时需要借助线程池。

mythread* pth = new Mythread();
QThreadPool::globalinstance()->start(pth);

注意：

 这种创建线程的方法的最大缺点就是：不能使用QT的信号-槽机制，因为QRunnable不会继承QObject。但是这种方法的好处就是，可以让QThreadPool来管理线程，QThreadPool会自动的清理我们新建的QRunnable对象

方式三：moveToThread

派生于QObject，使用moveToThread方法，将QThread对象作为私有成员，在构造函数里moveToThread，然后启动线程。

this->moveToThread(&m_th);
m_th.start();

方式一的实现：

 thread01.h

#ifndef THREAD01_H
#define THREAD01_H
#include <QThread>
class Thread01 : public QThread
{
     Q_OBJECT;
public:
    Thread01();
    void run() override;
};
#endif // THREAD01_H

thread01.cpp

#include "thread01.h"
#include <QDebug>
#include <iostream>
using namespace std;
Thread01::Thread01()
{
     cout<< "Thread01 construct fun" << QThread::currentThread() << endl;
}
void Thread01::run()
{
      cout<< "Thread01::run" << QThread::currentThread() << endl;
      int index  = 0;
      while(1)
      {
          qDebug() << index++;
          QThread::msleep(500);
      }
}

main.cpp

#include <QCoreApplication>
#include "thread01.h"
#include <iostream>
using namespace std;
int main(int argc, char *argv[])
{
    QCoreApplication a(argc, argv);
    cout<< "main thread" << QThread::currentThread() << endl;
    Thread01 th;
    th.start();
    cout<< "main thread end" << endl;
    return a.exec();
}

运行：

方式二的实现：

  thread02.h

#ifndef THREAD02_H
#define THREAD02_H
#include <QRunnable>
class Thread02 : public QRunnable
{
public:
    Thread02();
    ~Thread02();
    void run() override;
};
#endif // THREAD02_H

thread02.cpp

#include "thread02.h"
#include <QThread>
#include <iostream>
using namespace std;
Thread02::Thread02()
{
    cout<< "Thread01 construct fun" << QThread::currentThread() << endl;
}
Thread02::~Thread02()
{
      cout<< "Thread01 destructor fun" << QThread::currentThread() << endl;
}
void Thread02::run()
{
     cout<< "Thread02 construct fun" << QThread::currentThread() << endl;
}

main.cpp

#include <QCoreApplication>
#include "thread01.h"
#include "thread02.h"
#include <iostream>
#include <QThreadPool>
using namespace std;
int main(int argc, char *argv[])
{
    QCoreApplication a(argc, argv);
    cout<< "main thread" << QThread::currentThread() << endl;
   /* Thread01 th;
    th.start();*/
   Thread02 *th = new Thread02();
   QThreadPool::globalInstance()->start(th);
    cout<< "main thread end" << endl;
    return a.exec();
}

运行：

方式三的实现

thread03.h

#ifndef THREAD03_H
#define THREAD03_H
#include <QObject>
#include <QThread>
class thread03 : public QObject
{
    Q_OBJECT
public:
    explicit thread03(QObject *parent = nullptr);
public slots:
    void fun();
signals:
private:
     QThread m_th;
};
#endif // THREAD03_H

thread03.cpp

#include "thread03.h"
#include <QDebug>
#include <iostream>
using namespace std;
thread03::thread03(QObject *parent)
    : QObject{parent}
{
    this->moveToThread(&m_th);
    m_th.start();
    cout<< "Thread03 construct fun" << QThread::currentThread() << endl;
}
void thread03::fun()
{
   cout<< "Thread03  fun" << QThread::currentThread() << endl;
   qDebug() << "func";
   int index = 0;
   while(1)
   {
       qDebug() << index++;
       QThread::msleep(300);
   }
}

widget.h

#ifndef WIDGET_H
#define WIDGET_H
#include <QWidget>
#include "thread03.h"
QT_BEGIN_NAMESPACE
namespace Ui { class Widget; }
QT_END_NAMESPACE
class Widget : public QWidget
{
    Q_OBJECT
public:
    Widget(QWidget *parent = nullptr);
    ~Widget();
private slots:
    void on_pushButton_clicked();
signals:
    void sig_fun();
private:
    Ui::Widget *ui;
    thread03* m_pTh03 = nullptr;
};
#endif // WIDGET_H

widget.cpp

#include "widget.h"
#include "ui_widget.h"
#include <iostream>
using namespace std;
Widget::Widget(QWidget *parent)
    : QWidget(parent)
    , ui(new Ui::Widget)
{
    ui->setupUi(this);
    m_pTh03 = new thread03();
    connect(this,&Widget::sig_fun,m_pTh03,&thread03::fun);
}
Widget::~Widget()
{
    delete ui;
}
void Widget::on_pushButton_clicked()
{
     cout<< "on_pushButton_clicked" << QThread::currentThread() << endl;
     emit sig_fun();
}

界面和运行结果：