QT 多线程信号与槽（二）

一个主线程，一个次线程，主线程向次线程发送信号

mythread.h

#include <QThread>

#include <QDebug>

class Mythread : public QThread

{

Q_OBJECT

public:

Mythread();

protected:

void run();

private:

public slots:

void receive_main_signal(int);

};

mythread.cpp

#include "mythread.h"

#include <QDebug>

Mythread::Mythread()

{

qDebug()<<"Mythread:" <<QThread::currentThreadId();

//moveToThread(this);

}

void Mythread::run()

{

qDebug()<<"run:" <<QThread::currentThreadId();

exec();

}

void Mythread::receive_main_signal(int a)

{

qDebug()<<"from MainWindow:" <<QThread::currentThreadId();

qDebug()<<"i="<<a;

}

MainWindow.h

#include <QMainWindow>

#include "mythread.h"

namespace Ui {

class MainWindow;

}

class MainWindow : public QMainWindow

{

Q_OBJECT

public:

explicit MainWindow(QWidget *parent = 0);

~MainWindow();

private:

Ui::MainWindow *ui;

Mythread thread;

signals:

void emit_signal_to_thread(int);

public slots:

void start_thread();

};

MainWindow.cpp

#include "mainwindow.h"

#include "ui_mainwindow.h"

#include <QDebug>

MainWindow::MainWindow(QWidget *parent) :

QMainWindow(parent),

ui(new Ui::MainWindow)

{

ui->setupUi(this);

qDebug()<<"MainWindow:" <<QThread::currentThreadId();

connect(this,SIGNAL(emit_signal_to_thread(int)),&thread,SLOT(receive_main_signal(int)));//主线程给次线程发消息

connect(ui->pushButton,SIGNAL(clicked()),this,SLOT(start_thread()));

}

MainWindow::~MainWindow()

{

delete ui;

}

void MainWindow::start_thread()

{

thread.start();

int i;

for(i=0;i<10;i++)

{

emit emit_signal_to_thread(i);

sleep(1);

}

}

打印结果：

Mythread: 3063412432
MainWindow: 3063412432
from MainWindow: 3063412432
i= 0
run: 3018308496
from MainWindow: 3063412432
i= 1
from MainWindow: 3063412432
i= 2
from MainWindow: 3063412432
i= 3
from MainWindow: 3063412432
i= 4
from MainWindow: 3063412432
i= 5
from MainWindow: 3063412432
i= 6
from MainWindow: 3063412432
i= 7
from MainWindow: 3063412432
i= 8
from MainWindow: 3063412432
i= 9

结论：主线程向子线程发送信号，子线程对应的槽函数实现还是在主线程中完成的。如何使子线程的槽函数在子线程中完成呢？可以将mythread.cpp中moveToThread(this)的//去掉，最后可以显示：

Mythread: 3064174288
MainWindow: 3064174288
run: 3019070352
from MainWindow: 3019070352
i= 0
from MainWindow: 3019070352
i= 1
from MainWindow: 3019070352
i= 2
from MainWindow: 3019070352
i= 3
from MainWindow: 3019070352
i= 4
from MainWindow: 3019070352
i= 5
from MainWindow: 3019070352
i= 6
from MainWindow: 3019070352
i= 7
from MainWindow: 3019070352
i= 8
from MainWindow: 3019070352
i= 9

可见子线程的槽函数在新线程中运行了，没有出现在主线程中。但这种方法是被Bradley T. Hughes所唾弃的，所以还是用大家公认为比较对的方法吧。（见下篇）