how to clear a QPlainTextBox within a QTabWidget?

mzimmers

I'm afraid I don't understand. How do I know which one to call the clear on? In other words, what do I do with the index that denotes which tab is displayed?

SGaist

You don't need it, as I suggested, you can get the widget directly.

mzimmers

@SGaist right, I can do this:

    QWidget *w ;
...
    w = ui->tabWidget->currentWidget();

But what member/method of w gives me the child QPlainTextBox? That's the step I'm missing.

mpergand

The QPlainText should be the first child.

But, why not put the QPlainText directly as the tab widget ?

mzimmers

@mpergand I don't know how to do that, at least not with Designer.

But this seems to work, though I'm not sure it's what SGaist had in mind:

void Widget::on_pushButtonClear_clicked()
{
    QWidget *w ;
    QPlainTextEdit *qpte;

    w = ui->tabWidget->currentWidget();
    qpte = qobject_cast<QPlainTextEdit *>(w->children().at(0));
    qpte->clear();
}

Comments?

mpergand

In Designer, it seems impossible to change the default widget added automaticaly.
I'm missing something ?

mrjj

@mpergand
I think not. Only way i found was via promotion.

mrjj

@mzimmers

Just in case u call on_pushButtonClear_clicked twice..

if ( w->children().size() ) {
qpte = qobject_cast<QPlainTextEdit *>(w->children().at(0));
...
}

mpergand

@mrjj
Infortunately, you cannot promote to an already existing widget, QPlainTextEdit here.
A pity ...

mzimmers

Got it. Thanks for the assistance; perhaps the best lesson here is that there are still things one can't do in Designer.

mrjj

@mzimmers
Well its pretty easy to setup in code if really needed.
I often mix both UI design and code.
Thats what i like the best with Qt. Its not either WYSIWYG and no code
or reverse. Its actually only code. ;)

J.Hilk

@mzimmers said in how to clear a QPlainTextBox within a QTabWidget?:

void Widget::on_pushButtonClear_clicked()
{
    QWidget *w ;
    QPlainTextEdit *qpte;

    w = ui->tabWidget->currentWidget();
    qpte = qobject_cast<QPlainTextEdit *>(w->children().at(0));
    qpte->clear();
}

because this is bound to fail as soon as the first child is not the targeted widget, or if it does not have children at all, I would suggest the following change:

void Widget::on_pushButtonClear_clicked()
{
    QWidget *w ;
    QPlainTextEdit *qpte;

    w = ui->tabWidget->currentWidget();
    for(QObject *obj : w->children()){
         qpte = qobject_cast<QPlainTextEdit *>(obj);
         if(qpte)
              qpte->clear();
    }

SGaist

No need to make it so complicated: findChild is what you are looking for.

QWidget *w = ui->tabWidget->currentWidget();
QPlainTextEdit *qpte = w->findChild<QPlainTextEdit *>();
if (qpte) {
    qpte->clear();
}

Since the content of the widget is known, there's no real need for the if, it's to show good practice if you are doing "widget inspection".