Dynamic Handling of Hundreds of UI elements

[kshegunov]

@mrsurge
Hello,
For one you could make Qt do the casting for you:

QList<QLineEdit *> list = ui->doubleSpinBox->children<QLineEdit *>();
foreach (QLineEdit * item, list)
    item->installEventFilter(this);

And then in your event filter you could connect the dialog's accepted signal to the line edit:

bool MainWindow::eventFilter(QObject * obj, QEvent * event)
{
    if(event->type() == QEvent::MouseButtonPress)
    {
        Dialog mdialog;

        QSignalMapper mapper(&mdialog);
        mapper.setMapping(qobject_cast<QWidget *>(obj));
        QObject::connect(&mdialog, SIGNAL(accepted()), &mapper, SLOT(map()));
        QObject::connect(&mapper, SIGNAL(mapped(QWidget *)), this, SLOT(saveDataToLineEdit(QWidget *)));

        mdialog.exec();
    }
    return false;
}

void MainWindow::saveDataToLineEdit(QWidget * widget)
{
    QLineEdit * lineEdit = qobject_cast<QLineEdit *>(widget);
    Dialog * dialog = qobject_cast<Dialog *>(sender()->parent());
    // ... Transfer data between the dialog and the line edit here ...
}

Is this what you were asking for?

Kind regards.

EDIT:
I've moved the mapper to the stack, as it's not necessary to create it with new (since you're using a modal dialog).

[mrjj]

also be sure to check
http://www.qtcentre.org/threads/65146-Dynamic-Handling-of-Hundreds-of-UI-elements

[mrsurge]

@kshegunov

QList<QLineEdit *> list = ui->doubleSpinBox->children<QLineEdit *>();
foreach (QLineEdit * item, list)
    item->installEventFilter(this);

returns

**error: 'QLineEdit' does not refer to a value
QList<QLineEdit > list = ui->doubleSpinBox->children<QLineEdit >();

in my compiler. Remember I may be doing something really stupid, I'm new at qt

[kshegunov]

@mrsurge
No, the problem is with my code, it happens sometimes when I don't double-check my examples. The proper function to use would be QObject::findChildren. I usually use it similarly to this:

QList<QLineEdit *> list = ui->doubleSpinBox->findChildren<QLineEdit *>(QString(), Qt::FindDirectChildrenOnly);

This should compile fine.

Kind regards.

[mrsurge]

@kshegunov
your right that did compile just fine, but it only works for doubleSpinBox not doubleSpinBox_2 - doubleSpinBox_312

[kshegunov]

@mrsurge

Just apply the same principle:

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

    QList<QSpinBox *> sbList = findChildren<QSpinBox *>(QString(), Qt::FindDirectChildrenOnly);
    foreach (QSpinBox * spinBox, sbList)  {
            spinBox->installEventFilter(this);  //< Do you need this??

            QList<QLineEdit *> leList = spinBox->findChildren<QLineEdit *>(QString(), Qt::FindDirectChildrenOnly);
            foreach (QLineEdit * lineEdit, leList)
                lineEdit->installEventFilter(this);
    }
}

[mrsurge]

@kshegunov
This worked :

QList<QDoubleSpinBox *> sbList = ui->centralWidget->findChildren<QDoubleSpinBox *>(QString());
foreach (QDoubleSpinBox * spinBox, sbList)  {
            //spinBox->installEventFilter(this);  //< Do you need this??//<-no I don't

   QList<QLineEdit *> leList = spinBox->findChildren<QLineEdit *>(QString(), Qt::FindDirectChildrenOnly);
   foreach (QLineEdit * lineEdit, leList)
                lineEdit->installEventFilter(this);
}

many thanks for steering me in the right direction.

now on to saving the item to the specific line item

[kshegunov]

@mrsurge
Yes, of course, I forgot we're in a main window. Anyway, I'm glad it worked. One note, though, if possible use the QObject::findChildren with Qt::FindDirectChildrenOnly so Qt will not go about recursively looking for all. If your spin boxes are in layouts, but not inside other widgets, this should also work:

QList<QDoubleSpinBox *> sbList = ui->centralWidget->findChildren<QDoubleSpinBox *>(QString(), Qt::FindDirectChildrenOnly);

Kind regards.

[mrsurge]

@kshegunov

ok now how do I return a value from the dialog box to the doubleSpinBox that was clicked?

[kshegunov]

@mrsurge
I've provided some guidelines here.
If this is working,

QList<QLineEdit *> leList = spinBox->findChildren<QLineEdit *>(QString(), Qt::FindDirectChildrenOnly);

then the line edit has a QSpinBox for a parent. You have the line edit that'd been clicked here:

void MainWindow::saveDataToLineEdit(QWidget * widget)
{
    QLineEdit * lineEdit = qobject_cast<QLineEdit *>(widget);
    // ... Then the line edit parent is ...
    QSpinBox * spinBox = qobject_cast<QSpinBox *>(lineEdit->parent());
    // ... and so on ...
}

[mrsurge]

@kshegunov said:

bool MainWindow::eventFilter(QObject * obj, QEvent * event)
{
if(event->type() == QEvent::MouseButtonPress)
{
Dialog mdialog;

    QSignalMapper mapper(&mdialog);
    mapper.setMapping(qobject_cast<QWidget *>(obj));
    QObject::connect(&mdialog, SIGNAL(accepted()), &mapper, SLOT(map()));
    QObject::connect(&mapper, SIGNAL(mapped(QWidget *)), this, SLOT(saveDataToLineEdit(QWidget *)));

    mdialog.exec();
}
return false;

}

my compiler says

mapper.setMapping(qobject_cast<QWidget *>(obj));

requires a second argument

mapper.setMapping(qobject_cast<QWidget *>(obj),0);

works but i have no idea what thats doing

[kshegunov]

@mrsurge
Yes, I forgot the sender. That should be:

mapper.setMapping(&mdialog, qobject_cast<QWidget *>(obj));

QSignalMapper is a simple utility class to provide mapping of signals without parameters to signals/slots with a single parameter. This is done, because QDialog::accepted has no notion of the QLineEdit that triggers the event filter, so what the line does is simply to remap the signal to a slot that accepts the QLineEdit object as a parameter.

Kind regards.

[mrsurge]

@kshegunov

Ok I have a separate form, cpp, and .h for my dialog, does all this still apply? do i need to add anything to my dialog.cpp or .h?

[kshegunov]

@mrsurge
Hello,

Ok I have a separate form, cpp, and .h for my dialog, does all this still apply? do i need to add anything to my dialog.cpp or .h?

It shouldn't matter how you initialize the dialog, provided you call QDialog::accept() at the appropriate place, i.e. when a save/ok button is clicked.

Kind regards.