Add widget from custom class to MainWindow

[Tamfub]

Hi everyone.

I'm planning to create a form into MainWindow, and I need to add a field for an IPv4 address.
I've been looking for a smart way to handle this field and came across this solution, that seems suitable to me.

In the solution, the user creates a custom class IPCtrl that inherits from QFrame and keeps

QLineEdit *(m_pLineEdit[QTUTL_IP_SIZE])

i.e. a vector of 4 QLineEdits, one for each of the fields of the IP address.

I created a basic QT widget application (i.e. with main.cpp and mainwindow.h/.cpp/.ui), and created the new class.

Now, my goal is to show the QLineEdits inside my MainWindow. How can I do this? I tried to:

• add a private IPCtrl attribute in MainWindow, IPCtrl ip_field

• set it via a setter (thus requiring the copy constructor for IPCtrl)

• show it via ip_field.show()

But it results in two detached windows: MainWindow and ip_address.

I'm up for any clarification!

[mrjj]

Hi
The reason that ip_address becomes a window is that you dont give it a parent.
So to be inside MainWindow it needs to have that as a parent.

Normally you can do like this

in .h ( in mainwindow )
IPCtrl *ip_field;

in. cpp
ip_field = new IPCtrl(this);

and then it should be in Mainwinow.

Do note, that normally you use a layout in MainWidnow and you insert ip_field to such layout.

[Tamfub]

@mrjj Got it worked now, but an issue persists: now I have two ip_field's in my MainWindow, and I can't figure out why.

This is my code:

mainwindow.h

class MainWindow : public QMainWindow
{
    Q_OBJECT

public:
    explicit MainWindow(QWidget *parent = nullptr);
    ~MainWindow();
    IPCtrl ip_field;


private:
    Ui::MainWindow *ui;
};

mainwindow.cpp

MainWindow::MainWindow(QWidget *parent) :
    QMainWindow(parent),
    ui(new Ui::MainWindow)
{
    ui->setupUi(this);
    ip_field = new IPCtrl(this);
    ui->formLayout->addRow("IP Address", ip_field.window());
    ip_field.show();

}

mainwindow.ui

This is the result:

Only the ip_field at top calls the IPCtrl methods correctly.

[mrjj]

Hi
It seems that
ip_field.window()
returns something you insert into layout.

So you both have the one you new (top one) and
I would guess one that ip_field.window() returns.

Why are you using the .window() thing ?
what does it do ?

It would not accept just
ui->formLayout->addRow("IP Address", ip_field); ??

[Tamfub]

@mrjj No: documentation says

void QFormLayout::addRow(QWidget *label, QWidget *field)
Adds a new row to the bottom of this form layout, with the given label and field.

so it takes a QWidget as a second parameter, and I need a way to retrieve it from ip_field.

[mrjj]

@Tamfub
But is IPCtrl not based on QWidget ???
like
class IPCtrl : QWidget

?

[mrjj]

@mrjj

Ah saw link :)
well its
class IPCtrl : public QFrame

so yes you can use that directly.

[Tamfub]

@mrjj I know, but it complains:

[mrjj]

@Tamfub
Hi
the first parameter needs to be a QLabel and u give it a char *
also it seems that ip_field is not pointer ?

[Tamfub]

@mrjj Actually it is ok with the Char* in place of the QLabel, so I would put that apart for now.
I tried to:

• declare IPCtrl *ip_field (a pointer, as you suggested) in mainwindow.h

• write ui->formLayout->addRow("IP Address", ip_field->window()); ip_field->show(); (then with the arrows in place of the dots) in mainwindow.cpp

the application starts but the UI won't just appear...

[mrjj]

@Tamfub

Ok the window() part makes no sense to me.

Looking at the code, it just seems like a normal custom widget.
Did you change the code shown on SO or used it as is ?

[Tamfub]

@mrjj I used it as is, no changes.

[mrjj]

@Tamfub
Ok i did fast test.
It just compiles so not sure why you get so much grief from it :)

ui->formLayout->addRow("test", field);

test project.
https://www.dropbox.com/s/v0a5rdlkzi3igvb/IPCtrlTEst.zip?dl=0

[Tamfub]

@mrjj Ok, it worked also for me now, the error in addRow disappeares when ip_field is declared as a pointer. I did not try this XD

Thank you very much!

[mrjj]

@Tamfub
Np :)
yes it must be pointer OR you must use the & to take address but
due to how deletion works, it's best to use pointer :)

[Tamfub]

@mrjj Got it! Do you know why the right border of the textEdit is not visible?

[mrjj]

@Tamfub
It seems the last Edit touches the QFrames border.
but even if i make it HUGE, it still happens so its
its seems to be due to
pLayout->setContentsMargins( 0, 0, 0, 0 );
so you can fix it with
pLayout->setContentsMargins( 0, 0, 1, 0 );
Seems not to give ill side effects.

ps. in
IPCtrl::IPCtrl(QWidget *parent) : QFrame(parent)

[Tamfub]

@mrjj Fine, thank you again :)

[mrjj]

@Tamfub
Np.
please mark as solved if you got it working :)