qwt之QThread简单应用

好多时候，我们运算在子线程，控制和监控在界面，即主线程。

新建一个myThread，继续自QThread

myThread.h

#ifndef MYTHREAD_H
#define MYTHREAD_H

//#include <QObject>
#include <QThread>
#include <QDebug>

class myThread : public QThread
{
    Q_OBJECT
public:
    explicit myThread(QThread *parent = nullptr);
    void run();

signals:
    void setDoubleValue(double val);

};

#endif // MYTHREAD_H

myThread.cpp

#include "mythread.h"

myThread::myThread(QThread *parent) : QThread(parent)
{

}

void myThread::run()
{
    qDebug() << "start thread run";
    double val = .0;
    for(int i=0; i< 1000 ; i++)
    {
        for(int j=0; j< 10; j++)
        {
           val = i%9 + 0.5;
           //qDebug() << "i: " << i << " j: " << j << " val: " << val;
           emit setDoubleValue(val);
           msleep(100);
        }

    }
    qDebug() << "finish thread run";
}

mainWindow.h

#ifndef MAINWINDOW_H
#define MAINWINDOW_H

#include <QMainWindow>

#include "mythread.h"

QT_BEGIN_NAMESPACE
namespace Ui { class MainWindow; }
QT_END_NAMESPACE

class MainWindow : public QMainWindow
{
    Q_OBJECT

public:
    MainWindow(QWidget *parent = nullptr);
    ~MainWindow();

    myThread *mT;

private slots:
    void receiveDoubleValue(double val);

private:
    Ui::MainWindow *ui;
};
#endif // MAINWINDOW_H

mainWindow.cpp

#include "mainwindow.h"
#include "ui_mainwindow.h"

#include "opencv001.h"

#include <qwt_dial_needle.h>
#include <qwt_dial.h>

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

    QwtDialSimpleNeedle *needle = new QwtDialSimpleNeedle(QwtDialSimpleNeedle::Arrow );
    ui->Dial->setNeedle(needle);

    mT = new myThread();
    connect(mT, &myThread::setDoubleValue, this, &MainWindow::receiveDoubleValue);
    mT->start();

    opencv001 mCV;
    cv::Mat img = mCV.test3();
    int w = img.cols;
    int h = img.rows;
    int i, j;
    QImage *Image = new QImage(w, h, QImage::Format_RGB888);
    for(i=0;i<h;i++)
    {
        unsigned char *ptr = img.ptr<unsigned char>(i);
        for(j=0;j<w*3;j+=3)
        {
            Image->bits()[(Image->bytesPerLine()*i)+(j+2)] = ptr[j+2];
            Image->bits()[(Image->bytesPerLine()*i)+(j+1)] = ptr[j+1];
            Image->bits()[(Image->bytesPerLine()*i)+(j)] = ptr[j];
        }
    }
    ui->label->setPixmap(QPixmap::fromImage(*Image).scaled(ui->label->size()));

}

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

void MainWindow::receiveDoubleValue(double val)
{
    ui->Knob->setValue(val);
    //qDebug() << "receive: " << val;
}

这样，通过：

connect(mT, &myThread::setDoubleValue, this, &MainWindow::receiveDoubleValue)，把线程中的变化计算结果就可以显示到主界面上，线程中的计算就不会影响主线程的显示。

多谢，亲爱的美美。