How to Save Settings In Qt?

M4RZB4Ni

Hi,
i wrote some codes for an application
and i want to save this Settings Like Hide a lineEdit or etc...
and when reopen program last settings will load and when user edit setting
settings that saved updates
what i must do?

Mitchell

Hi,
You can use QSettings: http://doc.qt.io/qt-5/qsettings.html
This will allow you to save an objects state and then check that state when you start your program again.

Example:

QSetting mySettings;
lineEdit.hide;
mySettings.setValue("lineEdit", "hidden");

When you start the program can check settings in the constructor;

QSetting mySettings;
if( mySettings.value("lineEdit") == "hidden") {
    lineEdit.hide();
} else {
     lineEdit.show();
}

M4RZB4Ni

@Mitchell
thanks
but can you
Explain
this line?

mySettings.setValue("lineEdit", "hidden");

Mitchell

@M4RZB4Ni
It is a key value pair. So you are saving the value of "hidden" to "lineEdit". So i use this for a program where the user can connect to multiple servers.

Example:

QSettings mySettings;
	mySettings.setValue("server",p_Ui->serverSelector->currentIndex());

So here i set the value of "server" to the value that is in my serverSelector( This is a QComboBox). I can then set member variables to be = to the correct server. And when i launch the program i do:

QSettings mySettings;
	m_pUi->serverSelector->setCurrentIndex(mySettings.value("server").toInt());

this will load the value that i stored int mySettings.value("server"); This way i can preload the ui elements to what they had picked last time the program ran.

M4RZB4Ni

@Mitchell
Thank You So mush MR.MiTchell :)

M4RZB4Ni

@Mitchell
sorry
but when i wrote this code
showed me this error!
what i must do?
error: invalid use of void expression
QSettings settings;
settings.setValue("sss",ui->pushButton_3->setDisabled(true));
^

Mitchell

@M4RZB4Ni

ui->pushbutton_3->setDisabled(true);

This line of code is a command. It is setting the value of the button and has not return value;

From the documentation

QSettings settings;
settings.setValue("interval", 30);
settings.value("interval").toInt();     // returns 30

settings.setValue("interval", 6.55);
settings.value("interval").toDouble();  // returns 6.55

So you need to set a value. So every time you change the value visibility of the button you can update the settings. Or you can just update the settings in the destructor before you quit the program.
for example:

ui->pushButton_3->setDisabled(true);
settings.setValue("sss", ui->pushButton_3->isEnabled());

This will work because isEnabled(); will return a bool. So you will get a value of true or false;

Mitchell

@M4RZB4Ni
I made a new project to show you real context.

.h

#ifndef MAINWINDOW_H
#define MAINWINDOW_H

#include <QMainWindow>

namespace Ui {
	class MainWindow;
	}

class MainWindow : public QMainWindow
{
	Q_OBJECT

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

private:
	Ui::MainWindow *ui;
};

#endif // MAINWINDOW_H

.cpp

#include "mainwindow.h"
#include "ui_mainwindow.h"

#include <QSettings>

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

	//set default status of all ui elements
	ui->pushButton->setEnabled(mySettings.value("pushButton").toBool());
}

MainWindow::~MainWindow()
{
	QSettings mySettings;
	mySettings.setValue("pushButton",ui->pushButton->isEnabled());
	delete ui;
}

This will set the the pushbutton to be the value that is saved in mysettings when the program starts. And when the program closes it will save the current value of the button. This way when the program launches it will get the last state that the button was in.

Hope this will help clear it all up.

M4RZB4Ni

@Mitchell
hi,
i wrote this codes but settings dose not saved!
what is the problem?

Secretary::Secretary(QWidget *parent) :
    QWidget(parent),
    ui(new Ui::Secretary)
{

    ui->setupUi(this);
    ui->comboBox->setCurrentIndex(Settings.value("server").toInt());
}

Secretary::~Secretary()
{
    ui->comboBox->setCurrentIndex(Settings.value("server").toInt());
    delete ui;
}

void Secretary::on_comboBox_currentIndexChanged(int index)
{

    if(ui->comboBox->currentIndex()==2){
        ui->pushButton_3->setDisabled(true);
    }else if(ui->comboBox->currentIndex()==1){
        ui->pushButton_3->hide();

    }else if(ui->comboBox->currentIndex()==0){
        if(ui->lineEdit_56->text()==NULL){
            ui->pushButton_8->setDisabled(true);
        }
    }
 Settings.setValue("server",ui->comboBox->currentIndex());
}

raven-worx

i am not 100% sure, but i think you need to provide at least the organizational name (see QSettings constructors).
If you leave it out using the default constructor - like you are doing - you shoudl at least set it on the QApplication as a fallback.

Because using the QSettings default constructor uses the native format, which on Windows is the Registry.

M4RZB4Ni

@raven-worx
what i must do Exactly?
can you write a sample code for me?

the_

@raven-worx
Correct.
QSettings documentation says:

If QCoreApplication::setOrganizationName() and QCoreApplication::setApplicationName() has not been previously called, the QSettings object will not be able to read or write any settings, and status() will return AccessError.

@M4RZB4Ni

for example:

//main.cpp
int main(int argc, char *argv[])
{
    QApplication a(argc, argv);
    a.setApplicationDisplayName("My Tool");
    a.setOrganizationDomain("www.myurl.com");
    a.setOrganizationName("My Company");
    a.setApplicationName("My Application");
    a.setApplicationVersion("version x");
//continue with your code
}

If (on windows) you use the default format, wich is QSettings::NativeFormat the settings are stored in the Windows Registry in \HKEY_CURRENT_USER\Software\My Company\My Application

beecksche

@M4RZB4Ni

Copied from: http://doc.qt.io/qt-5/qsettings.html

When creating a QSettings object, you must pass the name of your company or organization as well as the name of your application. For example, if your product is called Star Runner and your company is called MySoft, you would construct the QSettings object as follows:

 QSettings settings("MySoft", "Star Runner");

If you use QSettings from many places in your application, you might want to specify the organization name and the application name using QCoreApplication::setOrganizationName() and QCoreApplication::setApplicationName(), and then use the default QSettings constructor:

    QCoreApplication::setOrganizationName("MySoft");
    QCoreApplication::setOrganizationDomain("mysoft.com");
    QCoreApplication::setApplicationName("Star Runner");
    ...
    QSettings settings;

I set the organization name and application name in my main entry function.

You can also group your entries:

If you want to save or restore many settings with the same prefix, you can specify the prefix using beginGroup() and call endGroup() at the end. Here's the same example again, but this time using the group mechanism:

    settings.beginGroup("mainwindow");
    settings.setValue("size", win->size());
    settings.setValue("fullScreen", win->isFullScreen());
    settings.endGroup();

    settings.beginGroup("outputpanel");
    settings.setValue("visible", panel->isVisible());
    settings.endGroup();

Hope this helps!

raven-worx

@M4RZB4Ni
for example in your main() method:

qApp->setOrganizationName("My Company Inc.");
qApp->setOrganizationDomain("mycompany.com");
qApp->setApplicationName("My Application");

or alternatively create one global static QSettings object (to avoid object creation everytime you want to access QSettings):

// in .h-File
class MainWindow : public QMainWidnow
{
     Q_OBJECT

public:
     static QSettings Settings;
};

// beginning of .cpp-File
QSettings MainWindow::Settings = QSettings("My Company Inc.", "My Application");

Then use

MainWindow::Settings.setValue( ... );
MainWindow::Settings.value( ... );

M4RZB4Ni

@raven-worx
@beecksche
@the_
@Mitchell
tnx
but if i want to save settings in a ini or xml file what i must do?

raven-worx

@M4RZB4Ni said:

but if i want to save settings in a ini or xml file what i must do?

read the docs in the first place.
See the QSettings constructors.

M4RZB4Ni

@raven-worx
@Mitchell

i wrote this codes but dose not work!

QSettings settings("Mobtakeran Fanavri KabooK","Kabook Physiothrapy");

Secretary::Secretary(QWidget *parent) :
QWidget(parent),
ui(new Ui::Secretary)
{

ui->setupUi(this);
ui->comboBox->setCurrentIndex(settings.value("comboBox").toInt());
}
Secretary::~Secretary()
{
    QCoreApplication::setOrganizationName("Mobtakeran Fanavri KabooK");
    QCoreApplication::setOrganizationName("WWW.M4RZB4Ni.IR");
    QCoreApplication::setApplicationName("Kabook Physiothrapy");

    delete ui;
}
void Secretary::on_comboBox_currentIndexChanged(int index)
{
settings.beginGroup("comboBox");
if(ui->comboBox->currentIndex()==2){
  ui->pushButton_3->setDisabled(true);
}else if(ui->comboBox->currentIndex()==1){
  ui->pushButton_3->hide();
  settings.setValue("comboBox",ui->comboBox->currentIndex());

}else if(ui->comboBox->currentIndex()==0){
    if(ui->lineEdit_56->text()==NULL){
       ui->pushButton_8->setDisabled(true);
    }
}
settings.endGroup();
}

What i must do?

Mitchell

look at what @the_ as well as @raven-worx. They both said that you need to set the organizationName in MAIN().
You are setting it in the destructor of your class. There is zero reason to have it there.

From @raven-worx
or example in your main() method:

qApp->setOrganizationName("My Company Inc.");
qApp->setOrganizationDomain("mycompany.com");
qApp->setApplicationName("My Application");

From @the_
int main(int argc, char *argv[])
{
QApplication a(argc, argv);
a.setApplicationDisplayName("My Tool");
a.setOrganizationDomain("www.myurl.com");
a.setOrganizationName("My Company");
a.setApplicationName("My Application");
a.setApplicationVersion("version x");
//continue with your code
}

This will set up the QSettings before you use it in any of the other classes you use. The purpose behind this is so it has something to name itself. So on mac if you go to $HOME/Library/Preferences/com.orgname.appname.plist

This is where you will actually be saving the settings to. So you need to set the OrganizationName before you use QSettings at all. SO the best place is in Main because it runs first. I am not sure where it gets saved to on windows you could probably do a google search to find that.

Mitchell

@M4RZB4Ni
I made a full example code for you so you can see one that works.
It has a button and a label. When you click the button it will hide or show the label. And when you close and reopen the program the label will be in the same state as when you closed the program.

main.cpp

#include "mainwindow.h"
#include <QApplication>


int main(int argc, char *argv[])
{
	QApplication app(argc, argv);
	app.setOrganizationDomain("sampleCompany.com");
	app.setOrganizationName(QLatin1String("sample Company"));
	app.setApplicationName(QLatin1String("Example Application"));
	MainWindow w;
	w.show();

	return app.exec();
}

mainWindow.h

#ifndef MAINWINDOW_H
#define MAINWINDOW_H

#include <QMainWindow>

namespace Ui {
	class MainWindow;
	}

class MainWindow : public QMainWindow
{
	Q_OBJECT

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

private slots:
	void on_pushButton_clicked();

private:
	Ui::MainWindow *ui;
};

#endif // MAINWINDOW_H

mainWindow.cpp

#include "mainwindow.h"
#include "ui_mainwindow.h"

#include <QSettings>

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

	//set default status of all ui elements
	bool value = mySettings.value("label").toBool();
	if (value == true) {
		ui->label->show();
	} else {
		ui->label->hide();
	}
}

MainWindow::~MainWindow()
{
	delete ui;
}

void MainWindow::on_pushButton_clicked()
{
	QSettings mySettings;
	if (ui->label->isVisible()) {
		ui->label->hide();
		mySettings.setValue("label", false);
	} else {
		ui->label->show();
		mySettings.setValue("label", true);
	}
}

Very minimal example that works. Hope this will clear everything up for you.

M4RZB4Ni

@Mitchell
@the_
@raven-worx
Thanks form all
my Problem solved!
thanks a lot :)