Problem with show Model-View-Deleaget inside MainWindow class

[TomASS]

Hello,

I'm trying code a Model-View-Deleage and I've one question:

When I'm writting this code:

QStandardItemModel model( 5, 2 );
    for( int r=0; r<5; r++ )
    for( int c=0; c<2; c++)
        {
            QStandardItem *item = new QStandardItem( QString("Row:%1, Column:%2").arg(r).arg(c) );
            if( c == 0 )
            for( int i=0; i<3; i++ )
            item->appendRow( new QStandardItem( QString("Item %1").arg(i) ) );
            model.setItem(r, c, item);
        }
 
    QTableView *table = new QTableView;
    table->setModel(&model);
    table->show();

QStandardItemModel model( 5, 2 );
    for( int r=0; r<5; r++ )
    for( int c=0; c<2; c++)
        {
            QStandardItem *item = new QStandardItem( QString("Row:%1, Column:%2").arg(r).arg(c) );
            if( c == 0 )
            for( int i=0; i<3; i++ )
            item->appendRow( new QStandardItem( QString("Item %1").arg(i) ) );
            model.setItem(r, c, item);
        }

    QTableView *table = new QTableView;
    table->setModel(&model);
    table->show();

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into a:

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

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

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then when application is running there are two windows. First whith:

MainWindow w;
    w.show();

MainWindow w;
    w.show();

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and the second with:

QTableView *table = new QTableView;
    table->setModel(&model);
    table->show();

QTableView *table = new QTableView;
    table->setModel(&model);
    table->show();

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and everything is ok, but, when I write a

QStandardItemModel model( 5, 2 );
    for( int r=0; r<5; r++ )
    for( int c=0; c<2; c++)
        {
            QStandardItem *item = new QStandardItem( QString("Row:%1, Column:%2").arg(r).arg(c) );
            if( c == 0 )
            for( int i=0; i<3; i++ )
            item->appendRow( new QStandardItem( QString("Item %1").arg(i) ) );
            model.setItem(r, c, item);
        }
 
    QTableView *table = new QTableView;
    table->setModel(&model);
    table->show();

QStandardItemModel model( 5, 2 );
    for( int r=0; r<5; r++ )
    for( int c=0; c<2; c++)
        {
            QStandardItem *item = new QStandardItem( QString("Row:%1, Column:%2").arg(r).arg(c) );
            if( c == 0 )
            for( int i=0; i<3; i++ )
            item->appendRow( new QStandardItem( QString("Item %1").arg(i) ) );
            model.setItem(r, c, item);
        }

    QTableView *table = new QTableView;
    table->setModel(&model);
    table->show();

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into:

MainWindow::MainWindow(QWidget *parent)
    : QMainWindow(parent), ui(new Ui::MainWindowClass)
{
    ui->setupUi(this);
//here!
 
}

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

}

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there are a empty window whith table->show() ? why?
when I'm trying put this code into button click:

void MainWindow::on_pushButton_clicked()
{
     QStandardItemModel model( 5, 2 );
    for( int r=0; r<5; r++ )
    for( int c=0; c<2; c++)
        {
            QStandardItem *item = new QStandardItem( QString("Row:%1, Column:%2").arg(r).arg(c) );
            if( c == 0 )
            for( int i=0; i<3; i++ )
            item->appendRow( new QStandardItem( QString("Item %1").arg(i) ) );
            model.setItem(r, c, item);
        }
 
    QTableView *table = new QTableView;
    table->setModel(&model);
    table->show();
}

void MainWindow::on_pushButton_clicked()
{
     QStandardItemModel model( 5, 2 );
    for( int r=0; r<5; r++ )
    for( int c=0; c<2; c++)
        {
            QStandardItem *item = new QStandardItem( QString("Row:%1, Column:%2").arg(r).arg(c) );
            if( c == 0 )
            for( int i=0; i<3; i++ )
            item->appendRow( new QStandardItem( QString("Item %1").arg(i) ) );
            model.setItem(r, c, item);
        }

    QTableView *table = new QTableView;
    table->setModel(&model);
    table->show();
}

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I get a empty window too :/

Thanks!

[vieraci]

You're not creating the table on anything.You need to give your table an owner.

QTableView *table = new QTableView(yourWindow);

QTableView *table = new QTableView(yourWindow);

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[wysota]

You are creating the model on stack so it gets deleted when you exit the constructor. Make it a member variable of the class as well or create it on heap.

[TomASS]

Thanks,

1. What should I write istead of "yourWindow" ?

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

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

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w?
this?
parent?

2. How I can add widget into MainWindow?

I'm trying w->addWidget, but it is no method addWidget :/

[wagmare]

2. How I can add widget into MainWindow?

I'm trying w->addWidget, but it is no method addWidget :/

setup all the widgets , layout it into a single widget "baaseWidget"
use mainWindow::setCentralWidget( baseWidget );
setCentralWidget()

[TomASS]

@vieraci:

You're not creating the table on anything.You need to give your table an owner.

thanks!
@wysota

You are creating the model on stack so it gets deleted when you exit the constructor. Make it a member variable of the class as well or create it on heap.

thanks! I've added model in member of the class, but how create it on a heap?
@wagmare:

setup all the widgets , layout it into a single widget "baaseWidget"
use mainWindow::setCentralWidget( baseWidget );
setCentralWidget()

How can I do this?

I'm trying:

MainWindow::MainWindow(QWidget *parent)
    : QMainWindow(parent), ui(new Ui::MainWindowClass)
{
  QVBoxLayout *layout = new QVBoxLayout( this );
  QDialogButtonBox *box = new QDialogButtonBox( Qt::Horizontal );
 
 
  layout->addWidget( new QLabel( "Try out the buttons!" ) );
  layout->addWidget( box );
}

MainWindow::MainWindow(QWidget *parent)
    : QMainWindow(parent), ui(new Ui::MainWindowClass)
{
  QVBoxLayout *layout = new QVBoxLayout( this );
  QDialogButtonBox *box = new QDialogButtonBox( Qt::Horizontal );

 
  layout->addWidget( new QLabel( "Try out the buttons!" ) );
  layout->addWidget( box );
}

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but I get a empty window :/

[TomASS]

for delete