keyPressEvent doesn't work

[8Observer8]

Hi

This is my steps:

- I created the "Qt Widget Application"
- I opened the "MainWindow.ui" file and put on it the "mdiArea"
- I created the "Qt Designer Form Class" and wrote in the "MainWindow.h" and "MainWindow.cpp" files:


private:
Ui::MainWindow *ui;
FirstWindow *m_firstWindow;
SecondWindow *m_secondWindow;
ThirdWindow *m_thirdWindow;


MainWindow.cpp


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

m_firstWindow = new FirstWindow;
m_secondWindow = new SecondWindow;
m_thirdWindow = new ThirdWindow;

QMdiSubWindow *w1 = ui->mdiArea->addSubWindow( m_firstWindow );
ui->mdiArea->addSubWindow( m_secondWindow );
ui->mdiArea->addSubWindow( m_thirdWindow );

ui->mdiArea->cascadeSubWindows();

w1->resize( 500, 500 );
}

- I opened "FirstWindow.h" and "FirstWindow.cpp" files and wrote:
FirstWindow.h


private:
Ui::FirstWindow *ui;
void keyPressEvent( QKeyEvent *event );
};

FirstWindow.cpp


void FirstWindow::keyPressEvent(QKeyEvent *event)
{
qDebug() << "keyPressEvent";
}

- I ran the application and pressed on the keys. But I didn't see the text "keyPressEvent" on the "Application Output"

Thank you!

[anda_skoa]

Does the FirstWindow instance have focus when you press a key?

Key events are delivered to the widget which has keyboard focus, see QApplication::focusWidget().

Cheers,
_

[8Observer8]

I clicked on the window with the name "First Window" and press the "Space" key. Nothing happened.

10577

Added after 11 minutes:

You are right. I added the button on the window:


void FirstWindow::on_pushButton_clicked()
{
qDebug() << focusWidget()->windowTitle();
}


Output:

""

I don't understand why.

[anda_skoa]

Window title is not really helpful.
Check the value of fodusWidget() vs. "this"

Cheers,
_

[budda]

not sure if this helps but
in your header file I thought event method classes were supposed to be:


protected:
void keyPressEvent( QKeyEvent *event );

private:

public:

[wysota]

I clicked on the window with the name "First Window" and press the "Space" key. Nothing happened.

Did you set QWidget::focusPolicy for the widget appropriately? If widget has Qt::NoFocus then it won't accept focus and thus won't receive key events.

[8Observer8]

I wrote it the constructor "setFocusPolicy( Qt::StrongFocus );"


FirstWindow::FirstWindow(QWidget *parent) :
QDialog(parent),
ui(new Ui::FirstWindow)
{
ui->setupUi(this);
setFocusPolicy( Qt::StrongFocus );
}

I added on the window the button:


void FirstWindow::on_pushButton_clicked()
{
if ( focusWidget() == this ) {
qDebug() << "focusWidget() == this";
} else {
qDebug() << "focusWidget() != this";
}
}


Output:


focusWidget() != this

[wysota]

When you click the button, it is most likely that the button gets the focus. Set the button's focus policy to Qt::NoFocus and try again. Better yet reimplement focusInEvent() and focusOutEvent() for your widget and print debug statements there to see when it receives and loses focus.

[8Observer8]

Yes, I see! I added Qt::NoFocus for the button:


FirstWindow::FirstWindow(QWidget *parent) :
QDialog(parent),
ui(new Ui::FirstWindow)
{
ui->setupUi(this);
setFocusPolicy( Qt::StrongFocus );
ui->pushButton->setFocusPolicy( Qt::NoFocus );
}


I added focusInEvent() and focusOutEvent():


#include "FirstWindow.h"
#include "ui_FirstWindow.h"
#include "QDebug"

FirstWindow::FirstWindow(QWidget *parent) :
QDialog(parent),
ui(new Ui::FirstWindow)
{
ui->setupUi(this);
setFocusPolicy( Qt::StrongFocus );
ui->pushButton->setFocusPolicy( Qt::NoFocus );
}

FirstWindow::~FirstWindow()
{
delete ui;
}

void FirstWindow::keyPressEvent( QKeyEvent *event )
{
qDebug() << "FirstWindow: keyPressEvent";
}

void FirstWindow::focusInEvent( QFocusEvent *event )
{
qDebug() << "FirstWindow: focusInEvent";
}

void FirstWindow::focusOutEvent( QFocusEvent *event )
{
qDebug() << "FirstWindow: focusOutEvent";
}

void FirstWindow::on_pushButton_clicked()
{
if ( focusWidget() == this ) {
qDebug() << "focusWidget() == this";
} else {
qDebug() << "focusWidget() != this";
}
}


When I click on the button I see:


focusWidget() == this


I will write in the constructor this insruction "setFocusPolicy( Qt::StrongFocus );" for all my MDI subwidnows