Qt Tutorial - Chapter 6: Building Blocks Galore!

    class LCDRange : public QVBox
    {
    public:
        LCDRange( QWidget *parent=0, const char *name=0 );
    };

The LCDRange widget is a widget without any API. It just has a constructor. This sort of widget is not very useful, so we'll add some API later.

    LCDRange::LCDRange( QWidget *parent, const char *name )
            : QVBox( parent, name )
    {
        QLCDNumber *lcd  = new QLCDNumber( 2, this, "lcd"  );
        QSlider * slider = new QSlider( Horizontal, this, "slider" );
        slider->setRange( 0, 99 );
        slider->setValue( 0 );
        connect( slider, SIGNAL(valueChanged(int)), lcd, SLOT(display(int)) );
    }

This is lifted straight from the MyWidget constructor in Chapter 5. The only differences are that the button is left out and the class is renamed.

    class MyWidget : public QVBox
    {
    public:
        MyWidget( QWidget *parent=0, const char *name=0 );
    };

MyWidget, too, contains no API except a constructor.

    MyWidget::MyWidget( QWidget *parent, const char *name )
            : QVBox( parent, name )
    {
        QPushButton *quit = new QPushButton( "Quit", this, "quit" );
        quit->setFont( QFont( "Times", 18, QFont::Bold ) );

        connect( quit, SIGNAL(clicked()), qApp, SLOT(quit()) );

The push button that used to be in what is now LCDRange has been separated so that we can have one "Quit" button and many LCDRange objects.

        QGrid *grid = new QGrid( 4, this );

We create a QGrid object with four columns. The QGRid widget automatically arranges its children in rows and columns; you can specify the number of rows or of columns, and QGrid will discover its new children and fit them into the grid.

        for( int r = 0 ; r < 4 ; r++ )
            for( int c = 0 ; c < 4 ; c++ )
                (void)new LCDRange( grid );

Four columns, four rows.

We create 4*4 LCDRanges, all of which are children of the grid object. The QGrid widget will arrange them.

    }

That's all.

Behavior