One signal to two window

kdbcz

Hello,

Please give me a simple example code for the following:

I have a "working thread" which has a variable.
I would like to display this variable on two different GUI window.
How can i do it?
It is working for me with one window, but how can I use the same working thread signal to the two windows at the same time?

andreyc

Connect the same signal in the second window slot and you will get both slots called on the signal.

kdbcz

Hello,

Thank You!
It is ok, i know, but I dont know how can I do it.
Where have to declare and start the working thread, to use it both connect function?
Sorry, but I never used before QT an C++ just C.

andreyc

It depends on the architecture of you app.
If it is a simple example that contains two windows then you can initialize everything in main() function()
start thread
create both windows
connect all necessary signals

"Here":http://mayaposch.wordpress.com/2011/11/01/how-to-really-truly-use-qthreads-the-full-explanation/ is a good explanation on how to use QThread in general.

And a simple example
@
class WindowOne : public QWidget
{
...
public slots:
void updateValue(int);
...
};

class WindowTwo : public QWidget
{
...
public slots:
void updateValue(int);
...
};

class Worker : public QObject
{
...
signals:
void valueChanged(int);
};

int main()
{
QApplication a(argc, argv);

QThread* thread = new QThread;
Worker* worker = new Worker;
WindowOne* winOne = new WindowOne;
WindowTwo* winTwo = new WindowTwo;

connect(worker, &Worker::valueChanged, winOne, &WindowOne::updateValue);
connect(worker, &Worker::valueChanged, winTwo, &WindowOne::updateValue);
worker->moveToThread(thread);
connect(thread, &QThread::started, worker, &Worker::process);
connect(worker, &QThread::finished, thread, &QThread::quit);
connect(worker, &QThread::finished, worker, &Worker::deleteLater);
connect(thread, &QThread::finished, thread, &QThread::deleteLater);

thread->start();
 
winOne->show();
winTwo->show();

// Start app event loop
return a.exec&#40;&#41;;

}
@

kdbcz

Thank You!

It is working now if I open both windows in the main.
How can I do it if I want to open the second window from a pushbutton of the first window?

andreyc

There are multiple solutions.
For example

create second window and connect all necessary signals inside first window constructor. I think signals are not delivered if a window is not shown.
In QPushButton::clicked() show second window.

kdbcz

I cant do it.

andreyc

What do you mean. Are there any errors?
Show what you have so far and we will help to fix it.

kdbcz

How can I use "QPushButton::clicked() show second window" in the main, if I have an UI window with that pushbutton? (I can open the second window from the first window, but than I cant make the connection between the worker thread and the second window with the same signal what iI use for the first window in the worker thread (because I initialized the worker in the main)).
I tried to send a signal from that pushbutton, but I cant do to the main.
My program is same now what you give me in the example.
Thank You!

andreyc

Add a pointer to Worker to WindowOne class. Initialize it in WindowOne constructor.
Use it when you opening second window.

kdbcz

It is working now. I initialize the worker and the second window in the first window constructor. And connect everything there.
Thank You!

kdbcz

Hello,
I have an other conection problem now.
I have a widget what I want to connect to my worker thread.
My thread is initialized in other class (Mainwindow).

widget .h:
@class RoverSatView : public QWidget
{
Q_OBJECT
public:
RoverSatView(QWidget *parent = 0);

protected:
void paintEvent(QPaintEvent *event);

private slots:
void slot_rtk_rover_sat_azel_in(const SatList &sats);

private:
    SatList satellites;
    rtk_thread worker;

};

widget .cpp:

RoverSatView::RoverSatView(QWidget *parent) : QWidget(parent)
{
connect(&worker,SIGNAL(rtk_rover_sat_azel(const SatList)),this,SLOT(slot_rtk_rover_sat_azel_in(const SatList)));
}@

No error message, but not working. What is the misstake?
Of course I have emit signal in the worker thread.

JohanSolo

connect(&worker,SIGNAL(rtk_rover_sat_azel(const SatList)),this,SLOT(slot_rtk_rover_sat_azel_in(const SatList)));

Did you register your SatList type?
By the way, there is no need to use the const in the connect statement.

andreyc

How do you assign worker from MainWindow to RoverSatView?
Are there any message in a console when you start the app?

kdbcz

Yes, the SatList type is registered.
No message in the consol.
I have this in the class RoverSatView header:
@ private:
rtk_thread worker;
@

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

QThread* rtkthread=new QThread;
rtk_thread* worker=new rtk_thread;

...
worker->moveToThread(rtkthread);
connect(rtkthread, SIGNAL(started()), worker, SLOT(run()));
connect(worker, SIGNAL(finished()), rtkthread, SLOT(quit()));
connect(worker, SIGNAL(finished()), worker, SLOT(deleteLater()));
connect(rtkthread, SIGNAL(finished()), rtkthread, SLOT(deleteLater()));
rtkthread->start();

}
@
@class RoverSatView : public QWidget
{
Q_OBJECT
public:
RoverSatView(QWidget *parent = 0);

protected:
void paintEvent(QPaintEvent *event);

private slots:
void slot_rtk_rover_sat_azel_in(const SatList &sats);

private:
    SatList satellites;
    rtk_thread worker;

};@

andreyc

You start thread for one worker object in MainWindow and connect signals from different worker object in RoverSatView.

kdbcz

How can I conect in RoverSatView to the same worker as in MainWindow?

andreyc

If RoverSatView is a member of MainWindow then you can declare worker as member of MainWindow and then pass it RoverSatView constructor.
If it is not then allocate worker before MainWindow, pass it to MainWindow ctor and to RoverSatView.

kdbcz

Hello,

How can I pass it if RoverSatView is a widget in a generated UI tabwidget?

arsinte_andrei

then where you have the generation code you simply take that variable from there - from the constructor and connect it. just after it was constructed or generated

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One signal to two window