keyPressEvent - how to override?

jenya7

@Christian-Ehrlicher said in keyPressEvent - how to override?:

@jenya7 said in keyPressEvent - how to override?:

I will take the line and send it serially.

simply emit a signal then, and do whatever you want in your slot: https://doc.qt.io/qt-5/signalsandslots.html
What slot? I need to check every typed character? how a slot is related to it?
We have an event especially designed for this purpose - keyPressEvent.

Ashok Kumar

Instead of overriding the keyPressEvent function you can override the eventFilter function.
bool eventFilter(QObject *obj, QEvent *ev) ;

and implement as below

bool eventFilter(QObject *obj, QEvent *event)
{
if (obj == MytextEdit)
{
if (event->type() == QEvent::KeyPress)
{
QKeyEvent keyEvent = static_cast<QKeyEvent>(event);
qDebug() << keyEvent->key();
return true;
}
else {

      return eventFilter(obj, event);
  }

}

Now after this you can go to your main form and create the object of Mytextedit and install event filter for the textedit object ...

jenya7

@Ashok-Kumar
Thank you. How do I install the event filter for the textedit object?

Ashok Kumar

@jenya7 you can create textedit object and do

textedit->installEventFilter(this);

jenya7

@Ashok-Kumar said in keyPressEvent - how to override?:

@jenya7 you can create textedit object and do

textedit->installEventFilter(this);

In mainwindow.cpp I do

bool eventFilter(QObject *obj, QEvent *event)
{
    if (obj == textEditTerminalTx) 
    {
        if (event->type() == QEvent::KeyPress) 
        {
            QKeyEvent keyEvent = static_cast<QKeyEvent>(event);
            //qDebug() << keyEvent->key();
            return true;
        } 
        else 
        {
            return false;
        }
    } 
    else 
    {
        // pass the event on to the parent class
        return eventFilter(obj, event);
    }
}

On this line obj == textEditTerminalTx I get - error: use of undeclared identifier 'textEditTerminalTx'
On this line QKeyEvent keyEvent = static_cast<QKeyEvent>(event); - I get error: no matching conversion for static_cast from 'QEvent *' to 'QKeyEvent'

Ashok Kumar

@jenya7 instead of doing casting like u did above QKeyEvent keyEvent = static_cast<QKeyEvent>(event);

instead u can do like this

QKeyEvent keyEvent=(QKeyEvent*)(event);
It will work

jenya7

@Ashok-Kumar said in keyPressEvent - how to override?:

@jenya7 instead of doing casting like u did above QKeyEvent keyEvent = static_cast<QKeyEvent>(event);

instead u can do like this

QKeyEvent keyEvent=(QKeyEvent*)(event);
It will work

This way I get - error: no viable conversion from 'QKeyEvent *' to 'QKeyEvent'

Ah I see - QKeyEvent keyEvent = (QKeyEvent)(event); - the site editor removes a pointer star.

And why the object not visible in the scope - if (obj == textEditTerminalTx) ?
I tried if (obj == ui->textEditTerminalTx) but ui also not visible.

Say in functions with MainWindow:: ui is visible like
void MainWindow::on_ButtonCompileScript_clicked()
{
QString text = ui->textEditScriptIn->toPlainText();
}

OK.

In mainwindow.h I added

public:
    bool eventFilter(QObject *obj, QEvent *event);

In mainwindow.cpp

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

bool MainWindow::eventFilter(QObject *obj, QEvent *event)
{
    QMessageBox mb;
    if (obj == ui->textEditTerminalTx)
    {
        if (event->type() == QEvent::KeyPress)
        {
            QKeyEvent *keyEvent = static_cast<QKeyEvent*>(event);
            if (keyEvent->key() == Qt::Key_Enter)
            {
                mb.setText("Enter");
                mb.exec();
            }
            return true;
        }
        else
            return false;
    }
    else
    {
        // pass the event on to the parent class
        return eventFilter(obj, event);
    }
}

But when I type - no char is typed in the widget and no reaction on Enter key.

Ashok Kumar

@jenya7 If u r getting no viable conversion from QKeyEvent* to QKeyEvent. include <QKeyEvent> headerfile in the mainwindow class

jenya7

@Ashok-Kumar said in keyPressEvent - how to override?:

@jenya7 If u r getting no viable conversion from QKeyEvent* to QKeyEvent. include <QKeyEvent> headerfile in the mainwindow class

I do get the event. To test it I added

if (event->type() == QEvent::KeyPress)
        {
            QKeyEvent *keyEvent = static_cast<QKeyEvent*>(event);
            if (keyEvent->key() == Qt::Key_Return)
            {
                mb.setText("Enter");
                mb.exec();
            }
            else
            {
                term_str += static_cast<char> (keyEvent->key());
                ui->textEditTerminalTx->setText(term_str);
            }
            return true;
        }
        else
            return false;

When I type I get chars in the widget but it types also backspase and delete keys instead of action. And on Key_Return I see the message box.

Ashok Kumar

@jenya7
if u want only chars in the QTextedit then u can use try this

if(keyevent->key()>=Qt::Key_0 && keyevent->key()<=Qt::Key_9)

if u want only digits in the QTextedit then u can use try this

if(keyevent->key()>=Qt::Key_A && keyevent->key()<=Qt::Key_Z)...

If u create the QMessageBox object in the constructor then it will be shown in the beginning itself

jenya7

@Ashok-Kumar said in keyPressEvent - how to override?:

@jenya7
if u want only chars in the QTextedit then u can use try this

if(keyevent->key()>=Qt::Key_0 && keyevent->key()<=Qt::Key_9)

if u want only digits in the QTextedit then u can use try this

if(keyevent->key()>=Qt::Key_A && keyevent->key()<=Qt::Key_Z)...

If u create the QMessageBox object in the constructor then it will be shown in the beginning itself

to get every possible key I did so

if (keyEvent->key() != Qt::Key_Backspace && keyEvent->key() != Qt::Key_Delete)
 {
            term_str += static_cast<char> (keyEvent->key());
           ui->textEditTerminalTx->setText(term_str);
 }

but the keys Backspace and Delete don't act as suppose to be - no action - it suppose to delete chars.
Also it gets chars only in upper case ignoring CapsLock selection.

This way it works

bool MainWindow::eventFilter(QObject *obj, QEvent *event)
{
    QMessageBox mb;
    if (obj == ui->textEditTerminalTx)
    {
        if (event->type() == QEvent::KeyPress)
        {
            QKeyEvent *keyEvent = static_cast<QKeyEvent*>(event);
            if (keyEvent->key() == Qt::Key_Return)
            {

                mb.setText("Enter");
                mb.exec();
            }
            else
            {
                //term_str += static_cast<char> (keyEvent->key());
                return false;
            }
        }
        else
            return false;
    }
    else
        // pass the event on to the parent class
        return MainWindow::eventFilter(obj, event);
}

Ashok Kumar

@jenya7 What exactly is your problem. Which keys do you need to use in textedit . can u elaborate it .

jenya7

@Ashok-Kumar said in keyPressEvent - how to override?:

@jenya7 What exactly is your problem. Which keys do you need to use in textedit . can u elaborate it .

The last function's version solves the problem - I get all the chars and keys Backspase and Delete work.
Now - on Enter key - I'd like to take the line before the Enter key and send it. Looking how to get the line before the Enter key. Trivial things so difficult in Qt... :)

Ashok Kumar

@jenya7 If u want the text before the enter key then you have to emit signal with parameter as string and write a particular slot for that and there u can get that text...

signal:
void textBeforeEnter(QString);

slot :
void getText(QString);

connect(this,SIGNAL(textBeforeEnter(QString)),this,SLOT(getText(QString)));
emit textBeforeEnter(textedit.text);

void getText(QString text)
{
qDebug()<<"The text in textedit before pressing enter key is "<<text<<endl;
}