event(QEvent * event)

[camel]

And here you got a version that uses eventfilters:

#include "qapplication.h"
#include "qlabel.h"
#include "qtabwidget.h"
 
class MyEventFilter : public QObject
{
    Q_OBJECT
public:
    MyEventFilter(QWidget *parent = 0, const char *name = 0)
        : QObject(parent, name) { }
 
    bool eventFilter(QObject *watched, QEvent *e)
    {
        if (watched->inherits("QTabWidget")) {
            QTabWidget *tab = (QTabWidget*)watched;
            if(e->type() == QEvent::KeyPress) {
                QKeyEvent *k = (QKeyEvent*)e;
                Qt::Key keyPressed = (Qt::Key)k->key();
                if (keyPressed == Qt::Key_Left) {
                    int indx = tab->currentPageIndex();
                    tab->setCurrentPage ((indx ==0)?tab->count():indx-1 ) ;
                    return true;
 
                } else if (keyPressed == Qt::Key_Right) {
                    int indx = tab->currentPageIndex();
                    tab->setCurrentPage ((indx+1)%tab->count() );
                    return true;
                }
            }
        }
        return false;
    }
};
 
int main(int argc, char* argv[])
{
    QApplication app(argc, argv);
 
    QTabWidget *tab = new QTabWidget;
 
    QLabel *label1 = new QLabel("Label1", tab);
    tab->addTab(label1, "Label1");
 
    QLabel *label2 = new QLabel("Label2", tab);
    tab->addTab(label2, "Label2");
 
    tab->installEventFilter(new MyEventFilter(tab));
 
    tab->show();
 
    return app.exec();
}
#include "main.moc"

#include "qapplication.h"
#include "qlabel.h"
#include "qtabwidget.h"

class MyEventFilter : public QObject
{
    Q_OBJECT
public:
    MyEventFilter(QWidget *parent = 0, const char *name = 0)
        : QObject(parent, name) { }

    bool eventFilter(QObject *watched, QEvent *e)
    {
        if (watched->inherits("QTabWidget")) {
            QTabWidget *tab = (QTabWidget*)watched;
            if(e->type() == QEvent::KeyPress) {
                QKeyEvent *k = (QKeyEvent*)e;
                Qt::Key keyPressed = (Qt::Key)k->key();
                if (keyPressed == Qt::Key_Left) {
                    int indx = tab->currentPageIndex();
                    tab->setCurrentPage ((indx ==0)?tab->count():indx-1 ) ;
                    return true;

                } else if (keyPressed == Qt::Key_Right) {
                    int indx = tab->currentPageIndex();
                    tab->setCurrentPage ((indx+1)%tab->count() );
                    return true;
                }
            }
        }
        return false;
    }
};

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

    QTabWidget *tab = new QTabWidget;

    QLabel *label1 = new QLabel("Label1", tab);
    tab->addTab(label1, "Label1");

    QLabel *label2 = new QLabel("Label2", tab);
    tab->addTab(label2, "Label2");

    tab->installEventFilter(new MyEventFilter(tab));

    tab->show();

    return app.exec();
}
#include "main.moc"

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[camel]

Now that we have something which we can actually work with(and guess what the problem is) we can try out what is wrong.

What is wrong, is that the QTabWidget does not even get the left and right key-presses, since those are actually taken up by a child widget of its, QTabBar. To change the behaviour of the tabbar, we have to install an eventfilter onto it. And voila it works (As I would imaging you intendet...)

#include "qapplication.h"
#include "qlabel.h"
#include "qtabwidget.h"
#include "qtabbar.h"
#include "qtextedit.h"
 
class ABC : public QTabWidget
{
    Q_OBJECT
public:
    ABC(QWidget * parent = 0, const char * name = 0, WFlags f = 0)
        : QTabWidget(parent, name, f)
    {
        tabBar()->installEventFilter(this);
    }
 
    virtual bool eventFilter(QObject *watched, QEvent *e)
    {
        if (watched == tabBar()) {
 
            if(e->type() == QEvent::KeyPress) {
                QKeyEvent *k = (QKeyEvent*)e;
                Qt::Key keyPressed = (Qt::Key)k->key();
 
                if (keyPressed == Qt::Key_Left) {
                    int indx = currentPageIndex();
                    setCurrentPage ((indx==0)?count()-1:indx-1 ) ;
                    return true;
 
                } else if (keyPressed == Qt::Key_Right) {
                    int indx = currentPageIndex();
                    setCurrentPage ((indx+1)%count() );
                    return true;
                }
            }
        }
        return QTabWidget::eventFilter(watched, e);
    }
 
protected:
};
 
int main(int argc, char* argv[])
{
    QApplication app(argc, argv);
 
    ABC *abc = new ABC();
 
    QLabel *label1 = new QLabel("Label1", abc);
    abc->addTab(label1, "Label1");
 
    QLabel *label2 = new QLabel("Label2", abc);
    abc->addTab(label2, "Label2");
 
    QTextEdit *edit1 = new QTextEdit(abc);
    abc->addTab(edit1, "Edit1");
 
    abc->show();
 
    return app.exec();
}
 
#include "main.moc"

#include "qapplication.h"
#include "qlabel.h"
#include "qtabwidget.h"
#include "qtabbar.h"
#include "qtextedit.h"

class ABC : public QTabWidget
{
    Q_OBJECT
public:
    ABC(QWidget * parent = 0, const char * name = 0, WFlags f = 0)
        : QTabWidget(parent, name, f)
    {
        tabBar()->installEventFilter(this);
    }

    virtual bool eventFilter(QObject *watched, QEvent *e)
    {
        if (watched == tabBar()) {

            if(e->type() == QEvent::KeyPress) {
                QKeyEvent *k = (QKeyEvent*)e;
                Qt::Key keyPressed = (Qt::Key)k->key();

                if (keyPressed == Qt::Key_Left) {
                    int indx = currentPageIndex();
                    setCurrentPage ((indx==0)?count()-1:indx-1 ) ;
                    return true;

                } else if (keyPressed == Qt::Key_Right) {
                    int indx = currentPageIndex();
                    setCurrentPage ((indx+1)%count() );
                    return true;
                }
            }
        }
        return QTabWidget::eventFilter(watched, e);
    }

protected:
};

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

    ABC *abc = new ABC();

    QLabel *label1 = new QLabel("Label1", abc);
    abc->addTab(label1, "Label1");

    QLabel *label2 = new QLabel("Label2", abc);
    abc->addTab(label2, "Label2");

    QTextEdit *edit1 = new QTextEdit(abc);
    abc->addTab(edit1, "Edit1");

    abc->show();

    return app.exec();
}

#include "main.moc"

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[rajaraob]

Hi,
why is my eventFilters() on QTabWidget (..) is not able filter events of left and right arrows key board . where as same code is recognising up and down arrows
regards
raja rao

[camel]

Hi,
why is my eventFilters() on QTabWidget (..) is not able filter events of left and right arrows key board . where as same code is recognising up and down arrows

Because those events (left and right) are taken by the child widget. (The Tabbar) Since the tabbar does not care for the other key events, they are propagated to the qtabwidget.

This is why I had to install a event filter to override this behaviour (which you can only do through sub-classing, because this is the only way you can gain access to it.).