CODEWITHSUNDEEP
eventsqtkey
user682587
user682587

Reputation: 51

How to handle key press events with the QPlainTextEdit

I've been developing with QT for around a week now and am pleased to say that I'm picking it up really fast. I'm an intermediate C++ programmer but picking up some parts of QT is proving to be challenging. I need to process key press events from the QPlainTextEdit when the user presses enter and I presume that the solution will involve sub classing the widget. Can any of you smart guys give me a potential implementable solution?

Upvotes: 5

Views: 8022

Answers (4)

Olek
Olek

Reputation: 136

If you only need to handle some messages sent to the control - like the key-presses - there is no need to subclass it. You can alternatively use the event filtering mechanism. Here is a simple example:

  1. Provide virtual eventFilter method in one of your QObject-based classes (e.g. the window form class).

    bool MyWindow::eventFilter(QObject *watched, QEvent *event)
{
    if(watched == ui->myTargetControl)
    {
        if(event->type() == QKeyEvent::KeyPress)
        {
            QKeyEvent * ke = static_cast<QKeyEvent*>(event);
            if(ke->key() == Qt::Key_Return || ke->key() == Qt::Key_Enter)
            {
                // [...]
                return true; // do not process this event further
            }
        }
        return false; // process this event further
    }
    else
    {
        // pass the event on to the parent class
        return QMainWindow::eventFilter(watched, event);
    }
}

  2. Install your class as the event filter for the target control. Form constructor is usually a good place for this code. In the following snippet this refers to the instance of class in which you implemented the eventFilter method.

    ui->myTargetControl->installEventFilter(this);

Upvotes: 5

Piwaldo
Piwaldo

Reputation: 21

please try :

if (event->key() == Qt::Key_Return || event->key() == Qt::Key_Enter){
//do something
}

in your keyPressEvent() function.

Upvotes: 1

Arnold Spence
Arnold Spence

Reputation: 22272

To really understand Qt and event handling there are two key areas of the documentation you should read. The first is the overview on The Event System and the second is a very important bit which is a cleverly hidden link on that page for QCoreApplication::notify. They should really move that to the main page of the Event System documentation as it really makes things quite clear (to me at least).

Upvotes: 7

smerlin
smerlin

Reputation: 6566

i would try subclassing QPlainTextEdit and reimplementing QWidget::keyPressEvent:

void YourTextEdit::keyPressEvent ( QKeyEvent * event )
{
  if( event->key() == Qt::Key_Return )
  {
    // optional: if the QPlainTextEdit should do its normal action 
    // even when the return button is pressed, uncomment the following line
    // QPlainTextEdit::keyPressEvent( event )

    /* do your stuff here */
    event->accept();
  }
  else
    QPlainTextEdit::keyPressEvent( event )
}

Upvotes: 4

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