[Resolved] Create a base project to show a simple dialog starting from an empty project

[realtebo]

Hi !

I'm studying Qt 5.2. I downloaded the mingw "edition".

I need you help to have a step-by-step [and updated) info about starting a widget app.

I do this

• Start the QtCreator
• Choose the Other Projects -> Empty Qt Project
• Choose the source dir

Actually I got an empty .pro.
Ok.

Now I'd like to create just a dialog

• right-click on project name and add Qt->Qt Desgner Form Class
• I choose Dialog withouth buttons and leave othe properties untouched
• Add a button
• Save all
• right-click on project and add c++ -> c++ source file, calling it main.cpp

Now my .pro looks as:

@
FORMS +=
dialog.ui

HEADERS +=
dialog.h

SOURCES +=
dialog.cpp
main.cpp
@

The main question is: what's the best-practice code ?

I used this

@
#include "dialog.h"
#include <QApplication>

int main(int argc, char *argv[])
{
QApplication a(argc, argv);
Dialog w;
w.show();

return a.exec();

}
@

But i got this error:

bq. C:\Qt_Projects\Hello10\dialog.h:4: error: QDialog: No such file or directory
#include <QDialog>
^

What's the problem.. ?

[realtebo]

Oh ..... I was missing only this:

@
QT += widgets
@

But ... why Qt Creator can't rebuild the .pro 'automatically' ?

I found this info googling, but .. how can I understand with module is missing in .pro from error "QDialog is missing"?

[Sanchir Kartiev]

If this feature will be included in QT Creator, some problems been solved.

[JKSH]

Hi,

What you've done is correct. But for convenience, you can select Applications -> Qt Widgets Application to achieve the same result.

[quote]But … why Qt Creator can’t rebuild the .pro ‘automatically’ ?

I found this info googling, but .. how can I understand with module is missing in .pro from error “QDialog is missing”?[/quote]Qt Creator can't edit your .pro file automatically because it doesn't know which module QDialog is in, either.

To find out which module you need, you can search the documentation. I normally use Google, with the help of this "Chrome extension":http://qt-project.org/forums/viewthread/36199/.

To search offline, you can open Qt Creator and select_Help -> Index_. Then, search for the class you want.

Example: At the top of the QDialog reference (http://qt-project.org/doc/qt-5/qdialog.html ), it says "qmake: QT += widgets". This tells you what you need to add to your .pro file.

[realtebo]

Thanks.

Now I'm going on editing the form.

I have a label, a lineEdit, two pushButtons, and a h-spacer.

I'm starting to try to use lineEdit validator.
I write

@
QRegExp regExp("[A-Za-z][1-9][0-9]{0,2}");
lineEdit->setValidator(new QRegExpValidator(regExp, this));
@

But when I compile I got 2 errors

bq.
C:\Qt_Projects\Hello10\dialog.cpp:1: In file included from ..\Hello10\dialog.cpp:1:0:
C:\Qt_Projects\Hello10\dialog.h:15: error: 'QLineEdit' does not name a type
QLineEdit *lineEdit;
^

and

bq.
C:\Qt_Projects\Hello10\dialog.cpp:-1: In constructor 'Dialog::Dialog(QWidget*)':
C:\Qt_Projects\Hello10\dialog.cpp:11: error: 'lineEdit' was not declared in this scope
lineEdit->setValidator(new QRegExpValidator(regExp, this));
^

Why? Probably, I think, because header file of the form doesn't declare the label itself.

So I open header file of the dialog. Actually it look like

@
#ifndef DIALOG_H
#define DIALOG_H

#include <QDialog>

namespace Ui {
class Dialog;
}

class Dialog : public QDialog
{
Q_OBJECT

public:
explicit Dialog(QWidget *parent = 0);
~Dialog();

private:
Ui::Dialog *ui;
};

#endif // DIALOG_H
@

So I tried to add into the "section" public this row

@
QLabel *label;
@

and the include at the top

@
#include <QLabel>
@

But the second error is still here

bq. ‘lineEdit’ was not declared in this scope

[realtebo]

Ok, I found the answer:

@
ui->lineEdit ....
@

Next step: signals

@
connect(ui->cancelButton, SIGNAL(clicked()), this, SLOT(reject()));
@

This time every thing works ok, but I cannot understand this why I don't need to declare in .h file .. ?

[JKSH]

[quote]I cannot understand this why I don't need to declare in .h file .. ?[/quote]Declare what?

The clicked() signal comes from the QPushButton header. It is is included by "ui_dialog.h", which is auto-generated from dialog.ui when you build your project.

You will need to declare your reject() slot in your dialog.h, and implement it in dialog.cpp

[realtebo]

ok, so signals already declared not need to be redeclared... yes, it's obvious now.

bq. You will need to declare your reject() slot ..

this is not mine, it's a default slot... like accept()

See: http://qt-project.org/doc/qt-5/qdialog.html#public-slots

I'm actually doing experiment extending QDialog, not a main window. So I can use the public slot of QDialog.

I'm closing thread as resolved