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# Listboxes and Comboboxes

This example program demonstrates how to use listboxes (with single selection and multi selection) and comboboxes (editable and non-editable).

Header file:

    /****************************************************************************
    ** $Id:  qt/listboxcombo.h   3.0.3   edited Oct 12 12:18 $
    **
    ** Copyright (C) 1992-2000 Trolltech AS.  All rights reserved.
    **
    ** This file is part of an example program for Qt.  This example
    ** program may be used, distributed and modified without limitation.
    **
    *****************************************************************************/

    #ifndef LISTBOX_COMBO_H
    #define LISTBOX_COMBO_H

    #include <qvbox.h>

    class QListBox;
    class QLabel;

    class ListBoxCombo : public QVBox
    {
        Q_OBJECT

    public:
        ListBoxCombo( QWidget *parent = 0, const char *name = 0 );

    protected:
        QListBox *lb1, *lb2;
        QLabel *label1, *label2;

    protected slots:
        void slotLeft2Right();
        void slotCombo1Activated( const QString &s );
        void slotCombo2Activated( const QString &s );

    };

    #endif

Implementation:

    /****************************************************************************
    ** $Id:  qt/listboxcombo.cpp   3.0.3   edited Oct 12 12:18 $
    **
    ** Copyright (C) 1992-2000 Trolltech AS.  All rights reserved.
    **
    ** This file is part of an example program for Qt.  This example
    ** program may be used, distributed and modified without limitation.
    **
    *****************************************************************************/

    #include "listboxcombo.h"

    #include <qcombobox.h>
    #include <qlistbox.h>
    #include <qhbox.h>
    #include <qpushbutton.h>
    #include <qstring.h>
    #include <qpixmap.h>
    #include <qlabel.h>
    #include <qimage.h>
    #include <qpainter.h>
    #include <qstyle.h>

    class MyListBoxItem : public QListBoxItem
    {
    public:
        MyListBoxItem()
            : QListBoxItem()
        {
            setCustomHighlighting( TRUE );
        }

    protected:
        virtual void paint( QPainter * );
        virtual int width( const QListBox* ) const { return 100; }
        virtual int height( const QListBox* ) const { return 16; }

    };

    void MyListBoxItem::paint( QPainter *painter )
    {
        // evil trick: find out whether we are painted onto our listbox
        bool in_list_box = listBox() && listBox()->viewport() == painter->device();

        QRect r ( 0, 0, width( listBox() ), height( listBox() ) );
        if ( in_list_box && isSelected() )
            painter->eraseRect( r );
        painter->fillRect( 5, 5, width( listBox() ) - 10, height( listBox() ) - 10, Qt::red );
        if ( in_list_box && isCurrent() )
            listBox()->style().drawPrimitive( QStyle::PE_FocusRect, painter, r, listBox()->colorGroup() );
    }

    /*
     * Constructor
     *
     * Creates child widgets of the ListBoxCombo widget
     */

    ListBoxCombo::ListBoxCombo( QWidget *parent, const char *name )
        : QVBox( parent, name )
    {
        setMargin( 5 );
        setSpacing( 5 );

        unsigned int i;
        QString str;

        QHBox *row1 = new QHBox( this );
        row1->setSpacing( 5 );

        // Create a multi-selection ListBox...
        lb1 = new QListBox( row1 );
        lb1->setSelectionMode( QListBox::Multi );

        // ...insert a pixmap item...
        lb1->insertItem( QPixmap( "qtlogo.png" ) );
        // ...and 100 text items
        for ( i = 0; i < 100; i++ ) {
            str = QString( "Listbox Item %1" ).arg( i );
            if ( !( i % 4 ) )
                lb1->insertItem( QPixmap( "fileopen.xpm" ), str );
            else
                lb1->insertItem( str );
        }

        // Create a pushbutton...
        QPushButton *arrow1 = new QPushButton( " -> ", row1 );
        // ...and connect the clicked SIGNAL with the SLOT slotLeft2Right
        connect( arrow1, SIGNAL( clicked() ), this, SLOT( slotLeft2Right() ) );

        // create an empty single-selection ListBox
        lb2 = new QListBox( row1 );

        QHBox *row2 = new QHBox( this );
        row2->setSpacing( 5 );

        QVBox *box1 = new QVBox( row2 );
        box1->setSpacing( 5 );

        // Create a non-editable Combobox and a label below...
        QComboBox *cb1 = new QComboBox( FALSE, box1 );
        label1 = new QLabel( "Current Item: Combobox Item 0", box1 );
        label1->setMaximumHeight( label1->sizeHint().height() * 2 );
        label1->setFrameStyle( QFrame::Panel | QFrame::Sunken );

        //...and insert 50 items into the Combobox
        for ( i = 0; i < 50; i++ ) {
            str = QString( "Combobox Item %1" ).arg( i );
            if ( i % 9 )
                cb1->insertItem( str );
            else
                cb1->listBox()->insertItem( new MyListBoxItem );
        }

        QVBox *box2 = new QVBox( row2 );
        box2->setSpacing( 5 );

        // Create an editable Combobox and a label below...
        QComboBox *cb2 = new QComboBox( TRUE, box2 );
        label2 = new QLabel( "Current Item: Combobox Item 0", box2 );
        label2->setMaximumHeight( label2->sizeHint().height() * 2 );
        label2->setFrameStyle( QFrame::Panel | QFrame::Sunken );

        // ... and insert 50 items into the Combobox
        for ( i = 0; i < 50; i++ ) {
            str = QString( "Combobox Item %1" ).arg( i );
            if ( !( i % 4 ) )
                cb2->insertItem( QPixmap( "fileopen.xpm" ), str );
            else
                cb2->insertItem( str );
        }

        // Connect the activated SIGNALs of the Comboboxes with SLOTs
        connect( cb1, SIGNAL( activated( const QString & ) ), this, SLOT( slotCombo1Activated( const QString & ) ) );
        connect( cb2, SIGNAL( activated( const QString & ) ), this, SLOT( slotCombo2Activated( const QString & ) ) );
    }

    /*
     * SLOT slotLeft2Right
     *
     * Copies all selected items of the first ListBox into the
     * second ListBox
     */

    void ListBoxCombo::slotLeft2Right()
    {
        // Go through all items of the first ListBox
        for ( unsigned int i = 0; i < lb1->count(); i++ ) {
            QListBoxItem *item = lb1->item( i );
            // if the item is selected...
            if ( item->isSelected() ) {
                // ...and it is a text item...
                if ( item->pixmap() && !item->text().isEmpty() )
                    lb2->insertItem( *item->pixmap(), item->text() );
                else if ( !item->pixmap() )
                    lb2->insertItem( item->text() );
                else if ( item->text().isEmpty() )
                    lb2->insertItem( *item->pixmap() );
            }
        }
    }

    /*
     * SLOT slotCombo1Activated( const QString &s )
     *
     * Sets the text of the item which the user just selected
     * in the first Combobox (and is now the value of s) to
     * the first Label.
     */

    void ListBoxCombo::slotCombo1Activated( const QString &s )
    {
        label1->setText( QString( "Current Item: %1" ).arg( s ) );
    }

    /*
     * SLOT slotCombo2Activated( const QString &s )
     *
     * Sets the text of the item which the user just selected
     * in the second Combobox (and is now the value of s) to
     * the second Label.
     */

    void ListBoxCombo::slotCombo2Activated( const QString &s )
    {
        label2->setText( QString( "Current Item: %1" ).arg( s ) );
    }

Main:

    /****************************************************************************
    ** $Id:  qt/main.cpp   3.0.3   edited Oct 12 12:18 $
    **
    ** Copyright (C) 1992-2000 Trolltech AS.  All rights reserved.
    **
    ** This file is part of an example program for Qt.  This example
    ** program may be used, distributed and modified without limitation.
    **
    *****************************************************************************/

    #include "listboxcombo.h"
    #include <qapplication.h>

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

        ListBoxCombo listboxcombo;
        listboxcombo.resize( 400, 270 );
        listboxcombo.setCaption( "Qt Example - Listboxes and Comboboxes" );
        a.setMainWidget( &listboxcombo );
        listboxcombo.show();

        return a.exec();
    }

See also Examples.