quit Qt application, not working

o6a6r9v1p

Implemented quit operation using a push button, but it is not working.
this is the line used :
connect(hCloseButton, SIGNAL(clicked()), this, SLOT(quit()));
this line is used in side a widget.
is it to be modified?
Thanks in advance.

JKSH

@o6a6r9v1p said in quit Qt application, not working:

connect(hCloseButton, SIGNAL(clicked()), this, SLOT(quit()));

What is this?

Are your trying to activate QCoreApplication::quit()?

mrjj

Hi
check the return from connect to see if its ok.
You tell is that "this" have a function quit()
is that true?
Maybe this should be application?

Did you try just to call close() ?

edit: @JKSH was faster :)

o6a6r9v1p

@mrjj

Inside user class, a push button is created to close the program itself, when necessary.
The statement is used in a function that belongs to the user class.

i tried close() also, but the program is not closing.

mrjj

@o6a6r9v1p
Ok but the user class should then connect to Application instance
so it would be
qDebug() << "quit conn:" << connect(ui->pushButton, SIGNAL(clicked()), qApp, SLOT(quit()));

and check it says
quit conn: true

o6a6r9v1p

@mrjj
thanks for the help. But it didnot work.
Compiler gives the error:
ui was not declared in this scope.

mrjj

@o6a6r9v1p

just use
hCloseButton
instead :)
the ui->butt was just from my sample to see that it did close.

You did read docs about connect ?
http://doc.qt.io/qt-5/signalsandslots.html

This is a MUST read if you are to use Qt.

o6a6r9v1p

I have this main function
@int main (int argc, char* argv[])
{

QApplication app(argc, argv);

// setLayout(verticalLayout);
// window.setWindowTitle(QApplication::translate("Device Monitor"));

myApp w;

// w.show();

return app.exec();

}
@

myApp is user class, in this "CLOSE" button is created. we want to use it , instead of using "X" in GUI to close the application.
we didnot use QT creator to generate GUI, we wrote it.

this is where difference comes between my code and examples & ideas given in the forum.

mrjj

Hi
Actually the X close the window
QApplication is set to exit exec()
when last top window is closed

It dont matter if u used UI file or programmed it.

But the shown connect
qDebug() << "quit conn:" << connect(ui->pushButton, SIGNAL(clicked()), qApp, SLOT(quit()));

will not close window but try to make whole app quit.

jsulm

@o6a6r9v1p See http://doc.qt.io/qt-5.8/qwidget.html#closeEvent

o6a6r9v1p

@mrjj
i did as you told, I got the following

when i used
@
connect(hCloseButton, SIGNAL(clicked()), this, SLOT(quit()));
@

it gave the message
"QObject::connect: No such slot myApp::quit()"

it compiles with no errors.
When Pushbutton is pressed it does not close the Application.

when i used
@
connect(hCloseButton, SIGNAL(clicked()), qApp, SLOT(quit()));
@
it did not compile.
it gave the error message
"qApp was not declared in this scope"

J.Hilk

@o6a6r9v1p

qApp is a global pointer referring to the unique application object. It is equivalent to QCoreApplication::instance(), but cast as a QApplication pointer, so only valid when the unique application object is a QApplication.

-> your main does not have a QApplication object

You said, you have no UI for the designer so I Asume you have a QCoreApplication in your main.

and try the following in it

//create a `myApp::quit()`
QCoreApplication::quit();

or

connect(quitButton, SIGNAL(clicked()), &app, SLOT(quit()));

mrjj

Hi
just include
#include <QApplication>
and its known.

Or as @J-Hilk says if that is the case :)

o6a6r9v1p

@mrjj
Thanks for your help.
I included <QApplication>
and
connect(hCloseButton, SIGNAL(clicked()), qApp, SLOT(quit()));
worked fine now.

"myApp" gui is closing now.