2

I have an application which runs 2 worker threads separate from the main GUI thread.

Thread 1:

  • needs to send some data to thread 2 every 100 ms.
  • sleeps for 10ms in each loop of its run.

Header:

class thread1:public QThread
{
    Q_OBJECT
public:
    thread1();
    ~thread1();

signals:
    void wakeThread2();
    void sendValue(int);
    void sleepThread2();

protected:
    void run();

private:
    volatile bool stop;
    int data;
};

Implementation:

thread1::thread1():stop(false),data(0)
{

}

void thread1::run()
{
    while(!stop)
    {
        ++data;
        if(data==1000)
            data = 0;
        cout<<"IN THREAD 1 with data = "<<data<<endl;
        emit sendValue(data);
        emit wakeThread2();
        emit sleepThread2();
        msleep(10);

    }
}

Thread 2

Header:

class thread2:public QThread
{
    Q_OBJECT
public:
    thread2();
    ~thread2();

private slots:
    void receiveValue(int);
    void Sleep();

protected:
    void run();

private:
    volatile bool stop;
    int data;
};

Implementation:

thread2::thread2():stop(false),data(0)
{

}

void thread2::run()
{
    if(!stop)
        cout<<"IN THREAD..............2  with data = "<<data<<endl;
}

void thread2::receiveValue(int x)
{
    data = x;
}

void thread2::Sleep()
{
    msleep(100);
}

MainWindow:

MainWindow::MainWindow(QWidget *parent) :
    QMainWindow(parent),
    ui(new Ui::MainWindow)
{
    ui->setupUi(this);

    t1 = new thread1;
    t2 = new thread2;

    QObject::connect(t1,SIGNAL(wakeThread2()),t2,SLOT(start()));
    QObject::connect(t1,SIGNAL(sendValue(int)),t2,SLOT(receiveValue(int)));
    QObject::connect(t1,SIGNAL(sleepThread2()),t2,SLOT(Sleep()));
}

MainWindow::~MainWindow()
{
    delete ui;
}

void MainWindow::on_pushButton_startT1_clicked()
{
    t1->start();
}

Output:

IN THREAD 1 with data = 1
IN THREAD..............2  with data = 1
IN THREAD 1 with data = 2
IN THREAD 1 with data = 3
IN THREAD 1 with data = 4
IN THREAD 1 with data = 5
IN THREAD 1 with data = 6
IN THREAD 1 with data = 7
IN THREAD 1 with data = 8
IN THREAD 1 with data = 9
IN THREAD 1 with data = 10
IN THREAD 1 with data = 11
IN THREAD..............2  with data = 2
IN THREAD 1 with data = 12
IN THREAD 1 with data = 13
IN THREAD 1 with data = 14
IN THREAD 1 with data = 15
IN THREAD 1 with data = 16
IN THREAD 1 with data = 17
IN THREAD 1 with data = 18
IN THREAD 1 with data = 19
IN THREAD 1 with data = 20

The data in thread 2 is not getting updated with the latest value of thread 1 and the GUI window is totally frozen. Please let me know if there is better/more efficient way to implement multi thread applications with Qt and to communicate between threads.

EDIT : ACCORDING TO LUCA the Thread1 remains almost the same...while Thread2.h looks like this

Thread2.h

#include <QThread>
#include <QTimer>
#include "iostream"

using namespace std;

class Thread2 : public QThread
{
    Q_OBJECT
public:
    Thread2();
    ~Thread2();
    void startThread();
public slots:
    void receiveData(int);
protected:
    void run();
private:
    volatile bool stop;
    int data;
    QTimer *timer;

};

and Implementation is....Thread2.cpp..

#include "thread2.h"

Thread2::Thread2():stop(false),data(0)
{
    timer = new QTimer;
    QObject::connect(timer,SIGNAL(timeout()),this,SLOT(start()));
}

Thread2::~Thread2()
{
    delete timer;
}

void Thread2::receiveData(int x)
{
    this->data = x;
}

void Thread2::run()
{
    cout<<"thread 2 .........data  =  "<<data<<endl;
}

void Thread2::startThread()
{
    timer->start(100);
}

and the mainwindow.cpp looks like this...

MainWindow::MainWindow(QWidget *parent) :
    QMainWindow(parent),
    ui(new Ui::MainWindow)
{
    ui->setupUi(this);

    t1 = new Thread1;
    t2 = new Thread2;

    QObject::connect(t1,SIGNAL(sendData(int)),t2,SLOT(receiveData(int)));
}

MainWindow::~MainWindow()
{
    delete ui;
}


void MainWindow::on_pushButton_start_thread1_clicked()
{
    t1->start();
    t2->startThread();
}
4

1 回答 1

1

在我看来，数据实际上已更新。但是线程 1 比线程 2 快 10 倍。当您发出 Sleep 信号时，线程 2 将进入睡眠状态 100ms，这使其无法处理其他信号。一旦控件返回事件循环，这些将被放置在队列中并进行处理。然后您将看到更新数据的消息。

无论如何，规范对我来说很奇怪：我读到“线程 1 需要每 100 毫秒向线程 2 发送数据......”，但我看到你每 10 毫秒执行一次，但后来你说“线程 1 本身休眠 10 毫秒”在其运行的每个循环中”。线程 1 在剩下的时间里应该做什么？

编辑：我不认为这正是你想要的，但我仍然不完全确定我理解你在寻找什么。不是一个完整或好的实现，只是给出一个想法：

#include <QCoreApplication>
#include <QTimer>
#include <QThread>

class Thread1 : public QThread
{
   Q_OBJECT
public:
   explicit Thread1() :
      data(0) {
      // Do nothing.
   }

   void run() {
      while (true) {
         data++;
         qDebug("Done some calculation here. Data is now %d.", data);
         emit dataChanged(data);
         usleep(10000);
      }
   }

signals:
   void dataChanged(int data);

private:
   int data;
};

class Thread2 : public QObject
{
   Q_OBJECT
public:
   explicit Thread2() {
      timer = new QTimer;
      connect(timer, SIGNAL(timeout()), this, SLOT(processData()));
      timer->start(100);
   }

   ~Thread2() {
      delete timer;
   }

public slots:
   void dataChanged(int data) {
      this->data = data;
   }

   void processData() {
      qDebug("Processing data = %d.", data);
   }

private:
   QTimer* timer;
   int data;
};

int main(int argc, char *argv[])
{
   QCoreApplication a(argc, argv);

   Thread1 t1;
   Thread2 t2;
   qApp->connect(&t1, SIGNAL(dataChanged(int)), &t2, SLOT(dataChanged(int)));
   t1.start();

   return a.exec();
}

#include "main.moc"

输出是：

Done some calculation here. Data is now 1.
Done some calculation here. Data is now 2.
Done some calculation here. Data is now 3.
Done some calculation here. Data is now 4.
Done some calculation here. Data is now 5.
Done some calculation here. Data is now 6.
Done some calculation here. Data is now 7.
Done some calculation here. Data is now 8.
Done some calculation here. Data is now 9.
Done some calculation here. Data is now 10.
Processing data = 10.
Done some calculation here. Data is now 11.
Done some calculation here. Data is now 12.
Done some calculation here. Data is now 13.
Done some calculation here. Data is now 14.
Done some calculation here. Data is now 15.
Done some calculation here. Data is now 16.
Done some calculation here. Data is now 17.
Done some calculation here. Data is now 18.
Done some calculation here. Data is now 19.
Processing data = 19.
Done some calculation here. Data is now 20.
Done some calculation here. Data is now 21.
Done some calculation here. Data is now 22.
Done some calculation here. Data is now 23.
Done some calculation here. Data is now 24.
Done some calculation here. Data is now 25.
Done some calculation here. Data is now 26.
Done some calculation here. Data is now 27.
Done some calculation here. Data is now 28.
Processing data = 28.
...

请注意 Thread2 实际上是应用程序的主线程（即 UI 线程）。如果需要，将对象移动到不同的线程。

于 2012-11-11T10:08:36.683 回答