How to put 2 Widgets in a MainWindow ?

[ChrisW67]

For a start you need to set the QMainWindow's central widget... there can be only one. To get more than one widget into the main window central area you need to encapsulate them.

#include <QtGui>
 
class mainwindow: public QMainWindow {
public:
    mainwindow(QWidget *p = 0): QMainWindow(p) {
        QWidget *central = new QWidget(this); // a central widget
        QLabel *widget1 = new QLabel("one widget", this);
        widget1->setFrameStyle(QFrame::Box | QFrame::Plain);
        QLabel *widget2 = new QLabel("two widget", this);
        widget2->setFrameStyle(QFrame::Box | QFrame::Plain);
 
        QVBoxLayout *layout = new QVBoxLayout(this);
        layout->addWidget(widget1);
        layout->addWidget(widget2);
 
        central->setLayout(layout); 
        setCentralWidget(central);   // you were missing this
    }
 
};
 
int main(int argc, char *argv[])
{
    QApplication app(argc, argv);
 
    mainwindow m;
    m.show();
 
    return app.exec();
}

#include <QtGui>

class mainwindow: public QMainWindow {
public:
    mainwindow(QWidget *p = 0): QMainWindow(p) {
        QWidget *central = new QWidget(this); // a central widget
        QLabel *widget1 = new QLabel("one widget", this);
        widget1->setFrameStyle(QFrame::Box | QFrame::Plain);
        QLabel *widget2 = new QLabel("two widget", this);
        widget2->setFrameStyle(QFrame::Box | QFrame::Plain);

        QVBoxLayout *layout = new QVBoxLayout(this);
        layout->addWidget(widget1);
        layout->addWidget(widget2);

        central->setLayout(layout); 
        setCentralWidget(central);   // you were missing this
    }

};

int main(int argc, char *argv[])
{
    QApplication app(argc, argv);

    mainwindow m;
    m.show();

    return app.exec();
}

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[gen_mass]

ok, thanks !!
when I put this code:

mainwindow::mainwindow(QWidget*p)
{
 
    double *buffer=NULL;
 
    plot=new Plot(100,250,buffer,buffer+1,this);
    data = new Data(250,buffer,this);
 
      QWidget *central = new QWidget(0); // a central widget.
 
      QVBoxLayout *layout = new QVBoxLayout(this);
      layout->addWidget(plot);
      layout->addWidget(data);
      central->setLayout(layout);
      setCentralWidget(central);  
 
     data->on_watcher();
 
}

mainwindow::mainwindow(QWidget*p)
{

    double *buffer=NULL;

    plot=new Plot(100,250,buffer,buffer+1,this);
    data = new Data(250,buffer,this);

      QWidget *central = new QWidget(0); // a central widget.

      QVBoxLayout *layout = new QVBoxLayout(this);
      layout->addWidget(plot);
      layout->addWidget(data);
      central->setLayout(layout);
      setCentralWidget(central);  

     data->on_watcher();

}

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I have exaclty what I want, but suddently the program shuts down with a code -1073741819 and I still get the error about the QLayout that Zlatomir talked about:

Starting C:\Users\Genevieve\Desktop\DETECTION\debug\DETECTION.exe...
QLayout: Attempting to add QLayout "" to mainwindow "", which already has a layout
C:\Users\Genevieve\Desktop\DETECTION\debug\DETECTION.exe exited with code -1073741819

Starting C:\Users\Genevieve\Desktop\DETECTION\debug\DETECTION.exe...
QLayout: Attempting to add QLayout "" to mainwindow "", which already has a layout
C:\Users\Genevieve\Desktop\DETECTION\debug\DETECTION.exe exited with code -1073741819

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When I debbuged with Visual it says:
Unhandled exception at 0x004056bc in DETECTION.exe: 0xC0000005: Access violation reading location 0x00000004.

[ChrisW67]

Make line 11 read:

QVBoxLayout *layout = new QVBoxLayout(central);

QVBoxLayout *layout = new QVBoxLayout(central);

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and the warning should go away.

The access violation is probably related to the buffer pointer; using it while it is NULL, accessing the "buffer+1" memory location, or trying to use the storage for the buffer pointer itself after it goes out of scope.

[gen_mass]

Ok, eveything works now!!!

just a last thing.. I want my plot to take 2/3 of the window andmy QTableWidget 1/3, is it possible to that with a QVBoxLayout ?

Thanks for your help !!!

[Zlatomir]

You can use something like this:

QSizePolicy PlotPolicy = plot->sizePolicy();
PlotPolicy.setVerticalStretch(1);                                   //don't remember the exact "formula", try with 1
plot->setSizePolicy(PlotPolicy);

QSizePolicy PlotPolicy = plot->sizePolicy();
PlotPolicy.setVerticalStretch(1);                                   //don't remember the exact "formula", try with 1
plot->setSizePolicy(PlotPolicy);

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if that doesn't do the right proportions, try this:

QSizePolicy PlotPolicy = plot->sizePolicy();
PlotPolicy.setVerticalStretch(2);                                   //don't remember the exact "formula", so play with this values
plot->setSizePolicy(PlotPolicy);
 
QSizePolicy DataPolicy = data->sizePolicy();
DataPolicy.setVerticalStretch(1);
plot->setSizePolicy(DataPolicy);

QSizePolicy PlotPolicy = plot->sizePolicy();
PlotPolicy.setVerticalStretch(2);                                   //don't remember the exact "formula", so play with this values
plot->setSizePolicy(PlotPolicy);

QSizePolicy DataPolicy = data->sizePolicy();
DataPolicy.setVerticalStretch(1);
plot->setSizePolicy(DataPolicy);

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[gen_mass]

Thanks Zlatomir !
I used your second method and it works well !!!

A last last question...is it possible to center my QTableWidget with that QVBoxLayout?
I want to do that because when I resize my window manually with a mouse, the QTableWidget stays align at the left.
Is there a similar function to

QTableWidget::setAlignement(Qt::AlignCenter)

QTableWidget::setAlignement(Qt::AlignCenter)

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that exists ?
I search the documentation, but couldn't find any easy way to do this