Accessing ui object from thread

[khelsys]

Hi all,
I'm really new of QT programming and I need to acess my ui pointer from a thread to refresh an image that's displayed in my window.
How can i do this? Many thanks to everyone who will help me
Gian

I post some code to explain it better:

MainWindow.h:

#ifndef MAINWINDOW_H
#define MAINWINDOW_H
 
#include <QtGui/QMainWindow>
 
namespace Ui
{
    class MainWindow;
}
 
class MainWindow : public QMainWindow
{
    Q_OBJECT
 
public:
    MainWindow(QWidget *parent = 0);
    ~MainWindow();
 
private:
    Ui::MainWindow *ui;
};
 
#endif // MAINWINDOW_H

#ifndef MAINWINDOW_H
#define MAINWINDOW_H

#include <QtGui/QMainWindow>

namespace Ui
{
    class MainWindow;
}

class MainWindow : public QMainWindow
{
    Q_OBJECT

public:
    MainWindow(QWidget *parent = 0);
    ~MainWindow();

private:
    Ui::MainWindow *ui;
};

#endif // MAINWINDOW_H

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MainWindow.cpp:

MainWindow::MainWindow(QWidget *parent)
    : QMainWindow(parent), ui(new Ui::MainWindow)
{
    ui->setupUi(this);
	MyThread* myT = new MyThread();
	myT->run();
}

MainWindow::MainWindow(QWidget *parent)
    : QMainWindow(parent), ui(new Ui::MainWindow)
{
    ui->setupUi(this);
	MyThread* myT = new MyThread();
	myT->run();
}

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getFrameThread.cpp:

void MyThread::run() 
    {
		forever {
			//MainWindow *ui = MainWindow::ui;
			CvCapture* camera;
			camera = cvCreateCameraCapture(0);
			assert(camera);
			IplImage * cvimage=cvQueryFrame(camera);
			assert(cvimage);
                        // IMG ELABORATION SKIPPED
			MainWindow::ui->imgLabel->setPixmap(CVUtils::getImage(cvimage)); // This is the row i want to fix
		}
    }

void MyThread::run() 
    {
		forever {
			//MainWindow *ui = MainWindow::ui;
			CvCapture* camera;
			camera = cvCreateCameraCapture(0);
			assert(camera);
			IplImage * cvimage=cvQueryFrame(camera);
			assert(cvimage);
                        // IMG ELABORATION SKIPPED
			MainWindow::ui->imgLabel->setPixmap(CVUtils::getImage(cvimage)); // This is the row i want to fix
		}
    }

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getFrameThread.h:

#include "CVUtils.h"
#include <QThread>
 
class MyThread : public QThread
    {
        Q_OBJECT
	public:
		MyThread();
 
    public:
        void run();
		MainWindow* ui;
    };

#include "CVUtils.h"
#include <QThread>

class MyThread : public QThread
    {
        Q_OBJECT
	public:
		MyThread();

    public:
        void run();
		MainWindow* ui;
    };

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[Ginsengelf]

Hi, you can't manipulate a widget from another thread than the main thread where the widget was created.

To solve your problem, create a slot in your main window to update the label and emit a signal instead of the MainWindow::ui->imgLabel->setPixmap(...) call.

Ginsengelf

[khelsys]

Hi, you can't manipulate a widget from another thread than the main thread where the widget was created.

To solve your problem, create a slot in your main window to update the label and emit a signal instead of the MainWindow::ui->imgLabel->setPixmap(...) call.

Ginsengelf

It's quite difficult for me.. Can you quickly explain how to do that in terms of places where to put the code (and what kind of code) ?
Thank you so much

Gian