I'm developing a Qt application and I'm really new to C++. What I'm trying to do, is create a class as a variable and then use its contents from another class.
My structure and what I'm trying to do, indicated by --> and <--:
mainwindow.h
#ifndef MAINWINDOW_H
#define MAINWINDOW_H
#include "settings.h"
namespace Ui {
class MainWindow;
}
class MainWindow : public QMainWindow {
Q_OBJECT
public:
-->BHSettings settings(qApp->applicationDirPath() + "/settings.ini");--<
explicit MainWindow(QWidget *parent = 0);
~MainWindow();
private:
Ui::MainWindow *ui;
};
#endif // MAINWINDOW_H
mainwindow.cpp
#include "mainwindow.h"
#include "ui_mainwindow.h"
MainWindow::MainWindow(QWidget *parent) : QMainWindow(parent), ui(new Ui::MainWindow) {
ui->setupUi(this);
}
MainWindow::~MainWindow() {
delete ui;
}
void MainWindow::doSomething() {
-->settings.loadSettings();<--
}
settings.h
#ifndef BHSETTINGS_H
#define BHSETTINGS_H
#include <QSettings>
class BHSettings : public QSettings {
public:
QString theme;
BHSettings(QString settingsFilePath);
void loadSettings();
void saveSettings();
void saveSettings();
};
#endif // BHSETTINGS_H
settings.cpp
#include "settings.h"
BHSettings::BHSettings(QString settingsFilePath) : QSettings(settingsFilePath, QSettings::IniFormat) {
loadSettings();
saveSettings();
}
void BHSettings::loadSettings() {
theme = getTheme();
}
void BHSettings::saveSettings() {
setValue("General/Theme", theme);
}
QString BHSettings::getTheme() {
return value("General/Theme", "default").toString();
}
I'm completely lost as how to do this. Some guidance as how to define another class to use its methods would be great.
You had a great start but since your BHSettings class has a non-default constructor, in order to have it as a member variable you should initialize it into your constructor's initialization list
MainWindow::MainWindow(QWidget *parent) :
QMainWindow(parent),
ui(new Ui::MainWindow),
settings(qApp->applicationDirPath() + "/settings.ini") <--
{
ui->setupUi(this);
}
you can't initialize it in the class declaration as an inline-declaration or something like you were doing.
Also notice that this will cause your settings object to be initialized (i.e. BHSettings's object constructed) each time you instantiate the MainWindow class
Declare the member in the class definition without the initialization code.
BHSettings settings;
Add the initialization code in the constructor of the class.
MainWindow::MainWindow(QWidget *parent) :
QMainWindow(parent), ui(new Ui::MainWindow),
settings(qApp->applicationDirPath() + "/settings.ini")
{
ui->setupUi(this);
}
You can use:
void MainWindow::doSomething() {
settings.loadSettings();
}
if you don't need the settings before that function. You may also call it in the constructor if that makes sense.
In your MainWindow class, define the variable:
public:
BHSettings settings;
In the constructor initialise this memeber:
MainWindow::MainWindow(QWidget *parent) : ... , settings(qApp->applicationDirPath() + "/settings.ini")
{
...
}
Related
Hi i have 3 classes that i want to use. but i dont want to create object of one class more than once. I directly want to use the object (in third class) of one class declared and initialized in second class.
To understand the problem please focus on NetworkConnection members and class defined in example below.
Class Mainwindow header
#ifndef MAINWINDOW_H
#define MAINWINDOW_H
#include <QMainWindow>
#include "secondscreen.h"
#include "networkconnection.h"
namespace Ui {
class MainWindow;
}
class MainWindow : public QMainWindow
{
Q_OBJECT
public:
explicit MainWindow(QWidget *parent = nullptr);
~MainWindow();
NetworkConnection *NetworkConnectionObject;
private slots:
void on_pushButton_clicked();
private:
Ui::MainWindow *ui;
SecondScreen* SecondScreenObject;
};
#endif // MAINWINDOW_H
Class Main Window cpp
#include "mainwindow.h"
#include "ui_mainwindow.h"
#include "QMessageBox"
#include "networkconnection.h"
MainWindow::MainWindow(QWidget *parent) :
QMainWindow(parent),
ui(new Ui::MainWindow)
{
ui->setupUi(this);
NetworkConnectionObject = new NetworkConnection();
}
MainWindow::~MainWindow()
{
delete ui;
}
void MainWindow::on_pushButton_clicked()
{
int Error = NetworkConnectionObject->Connect(Username,Password);
///////////////
// This Works
//////////////
NetworkConnectionObject->LogInToken = "";
}
Class NetworkConnection Header
#ifndef NETWORKCONNECTION_H
#define NETWORKCONNECTION_H
#include <QString>
class NetworkConnection
{
public:
NetworkConnection();
int Connect(QString Username, QString Passwd);
QString LogInToken;
};
#endif // NETWORKCONNECTION_H
Now i want to use Networkclassobject directly in SeconScreenclass so that i can access LogInToken Member of MainWindowInstance.
#include "secondscreen.h"
#include "ui_secondscreen.h"
#include "mainwindow.cpp"
SecondScreen::SecondScreen(QWidget *parent) :
QDialog(parent),
ui(new Ui::SecondScreen)
{
ui->setupUi(this);
///////////////
// This doesnot work
//////////////
MainWindow::NetworkConnectionObject->LogInToken = "";
}
SecondScreen::~SecondScreen()
{
delete ui;
}
However, when i try this compiler says
Invalid use of non-static data member "MainWindow::NetworkConnectionObject" Problem is i dont want to declare it static. Is there any way to do it.
Without seeing secondscreen.h I can't say for sure but MainWindow::NetworkConnectionObject" doesn't reference a specific instance of MainWindow class, you must reference a specific instance to modify.
If in your SecondScreen header you have something like
class SecondScreen {
// . . .
MainWindow window;
// . . .
}
then in your constructor for SecondScreen you must use the initialized instance of MainWindow, i.e.
SecondScreen::SecondScreen(QWidget* parent) : QDialog(parent) {
window.NetworkConnectionObject->LogInToken = "";
}
Welcome, I have a question about Qt's windows operations. I have a simple app which contains 2 windows:
MainWindow - includes push button, can't be resizeable,
AdminWindow - includes label, can be resizeable.
When I click push button, it should open AdminWindow and hide MainWindow. I made the app and it seems to work but when I open the AdminWindow, the application icon which is located in windows's bottom bar is missing. How can I fix it?
Icon is showed when MainWindow is opened:
mainwindow.h
#ifndef MAINWINDOW_H
#define MAINWINDOW_H
#include <QMainWindow>
#include "adminwindow.h"
namespace Ui {
class MainWindow;
}
class MainWindow : public QMainWindow
{
Q_OBJECT
public:
explicit MainWindow(QWidget *parent = 0);
~MainWindow();
private slots:
void on_pushButtonOpenAdmin_clicked();
private:
Ui::MainWindow *ui;
AdminWindow *adminWindow;
};
#endif // MAINWINDOW_H
mainwindow.cpp
#include "mainwindow.h"
#include "ui_mainwindow.h"
MainWindow::MainWindow(QWidget *parent) :
QMainWindow(parent),
ui(new Ui::MainWindow)
{
ui->setupUi(this);
}
MainWindow::~MainWindow()
{
delete ui;
}
// hides MainWindow and show AdminWindow
void MainWindow::on_pushButtonOpenAdmin_clicked()
{
hide();
adminWindow = new AdminWindow(this);
adminWindow->show();
}
adminwindow.h
#ifndef ADMINWINDOW_H
#define ADMINWINDOW_H
#include <QMainWindow>
namespace Ui {
class AdminWindow;
}
class AdminWindow : public QMainWindow
{
Q_OBJECT
public:
explicit AdminWindow(QWidget *parent = 0);
~AdminWindow();
private:
Ui::AdminWindow *ui;
};
#endif // ADMINWINDOW_H
adminwindow.cpp
#include "adminwindow.h"
#include "ui_adminwindow.h"
AdminWindow::AdminWindow(QWidget *parent) :
QMainWindow(parent),
ui(new Ui::AdminWindow)
{
ui->setupUi(this);
}
AdminWindow::~AdminWindow()
{
delete ui;
}
OK, let's start again...
I've created an project (Qt Widget Application) with Qt Creator.
My project structure:
myproject.pro
Headers
dialogform.h
mainwindow.h
Sources
dialogform.cpp
main.cpp
mainwindow.cpp
Forms
dialogform.h
mainwindow.h
When I click on DialogForm pushbutton, I need to call the clear() function from MainWindow
In my code below, my project is running, but, the clear() function does not clear the lineedit.
Do anyone known how can i fix this?
Thank you very much!
dialogform.h
#ifndef DIALOGFORM_H
#define DIALOGFORM_H
#include <QDialog>
namespace Ui {
class DialogForm;
}
class DialogForm : public QDialog
{
Q_OBJECT
signals:
void clearMainWindow();
public:
explicit DialogForm(QWidget *parent = 0);
~DialogForm();
private slots:
void on_pbClearLineEdit_clicked();
private:
Ui::DialogForm *ui;
};
#endif // DIALOGFORM_H
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();
public slots:
void clear();
private slots:
void on_pbCallDialog_clicked();
private:
Ui::MainWindow *ui;
};
#endif // MAINWINDOW_H
dialogform.cpp
#include "dialogform.h"
#include "ui_dialogform.h"
#include "mainwindow.h"
DialogForm::DialogForm(QWidget *parent) :
QDialog(parent),
ui(new Ui::DialogForm)
{
ui->setupUi(this);
}
DialogForm::~DialogForm()
{
delete ui;
}
void DialogForm::on_pbClearLineEdit_clicked()
{
connect(); // need help here. I'm using Qt 5.6.1
}
main.cpp
#include "mainwindow.h"
#include <QApplication>
int main(int argc, char *argv[])
{
QApplication a(argc, argv);
MainWindow w;
w.show();
return a.exec();
}
mainwindow.cpp
#include "mainwindow.h"
#include "ui_mainwindow.h"
#include "dialogform.h"
MainWindow::MainWindow(QWidget *parent) :
QMainWindow(parent),
ui(new Ui::MainWindow)
{
ui->setupUi(this);
}
MainWindow::~MainWindow()
{
delete ui;
}
void MainWindow::on_pbCallDialog_clicked()
{
DialogForm *dialogForm = new DialogForm(this);
dialogForm->show();
}
void MainWindow::clear()
{
ui->lineEdit->clear();
}
myfunction accesses an attribute of class myfile. Therefore it either needs to be a method of myfile as well, or it could be a friend function of the class myfile. In the latter case, however, you would need to give the relevant instance of myfile to myfunction as an argument. All usages of myfunction would need to be updated in either case.
The solution:
DialogForm::DialogForm(QWidget *parent) :
QDialog(parent),
ui(new Ui::DialogForm)
{
ui->setupUi(this);
connect(ui->pbClearLineEdit, &QPushButton::clicked, static_cast<MainWindow*>(parent), &MainWindow::clear);
}
I am trying to access the ui elements of different class but getting error message. I've tried to do this for many hours but still failing, I feel that I am missing something simple.
I am trying to access an element "label" which is in form.h
mainwindow:
#include "mainwindow.h"
#include "ui_mainwindow.h"
#include "form.h"
MainWindow::MainWindow(QWidget *parent) :
QMainWindow(parent),
ui(new Ui::MainWindow)
{
ui->setupUi(this);
Form * elemForm = new Form(this);
elemForm->ui; // works
//elemForm->ui->label; // does not work
}
MainWindow::~MainWindow()
{
delete ui;
}
form.h
#ifndef FORM_H
#define FORM_H
#include <QWidget>
namespace Ui {
class Form;
}
class Form : public QWidget
{
Q_OBJECT
public:
explicit Form(QWidget *parent = 0);
~Form();
Ui::Form *ui;
private:
};
#endif // FORM_H
form.cpp
#include "form.h"
#include "ui_form.h"
Form::Form(QWidget *parent) :
QWidget(parent),
ui(new Ui::Form)
{
ui->setupUi(this);
ui->label; //works fine here
}
Problem is in mainwindow file. I know this is inappropriate code, I'm just interested what I'm doing wrong. I am struggling to find whats wrong, any ideas?
In addition to form.h, you should also include ui_form.h in your MainWindow.h.
That's because the form elements are all defined in Ui::Form which is accessible by including :
#include "ui_form.h"
Please, try to think on what are you doing, and how to do things better.
Don't feel think that method explained by Nejat is controversial to OOP? If you are trying to use OOP, learn how to do it and use it.
To get deeper understanding on what am I talking about, please, read this short story about encapsulation.
Back to your example. Here is clean, simple and easy way to do what you want:
Your mainwindow.h:
#include "mainwindow.h"
#include "ui_mainwindow.h"
// Include only header of your Form, not ui_form.h!
#include "form.h"
MainWindow::MainWindow(QWidget *parent) :
QMainWindow(parent),
ui(new Ui::MainWindow)
{
ui->setupUi(this);
Form* elemForm = new Form(this);
// Use public method of your Form object!
elemForm->changeUI();
}
Your form.h:
#include <QWidget>
namespace Ui {
class Form;
}
class Form : public QWidget
{
Q_OBJECT
public:
explicit Form(QWidget *parent = 0);
~Form();
void changeUI(); // here you can do all what you want with your UI
private:
Ui::Form *ui;
};
in form.cpp you'll have realization:
void Form::changeUI()
{
ui->... // do all what you want with UI
}
I am currently learning Qt and I seem to have run into a problem.
In my practice project I have 2 classes: MainWindow and Dialog.
MainWindow.h
#ifndef MAINWINDOW_H
#define MAINWINDOW_H
#include <QMainWindow>
#include "dialog.h"
namespace Ui {
class MainWindow;
}
class MainWindow : public QMainWindow
{
Q_OBJECT
public:
explicit MainWindow(QWidget *parent = 0);
~MainWindow();
private slots:
void on_pushButtonDialog_clicked();
private:
Ui::MainWindow *ui;
Dialog *dialogInstance;
};
#endif // MAINWINDOW_H
MainWindow.cpp
#include "mainwindow.h"
#include "ui_mainwindow.h"
MainWindow::MainWindow(QWidget *parent) :
QMainWindow(parent),
ui(new Ui::MainWindow)
{
ui->setupUi(this);
dialogInstance = new Dialog(this);
}
MainWindow::~MainWindow()
{
delete ui;
}
void MainWindow::on_pushButtonDialog_clicked()
{
dialogInstance->show();
}
Dialog.h
#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
Dialog.cpp
#include "dialog.h"
#include "ui_dialog.h"
Dialog::Dialog(QWidget *parent) :
QDialog(parent),
ui(new Ui::Dialog)
{
ui->setupUi(this);
}
Dialog::~Dialog()
{
delete ui;
}
My goal is to input a value using the Dialog window, then have the value of that input shown on the MainWindow, I know how to pass variables around within the class using widgets, but I am not sure how to transfer variables between unrelated objects.
Any input would be of great help.
Try this:
#include "mainwindow.h"
#include "ui_mainwindow.h"
MainWindow::MainWindow(QWidget *parent) :
QMainWindow(parent),
ui(new Ui::MainWindow)
{
ui->setupUi(this);
connect(ui->pushButtonDialog, SIGNAL(clicked()), this, SLOT(on_pushButtonDialog_clicked()));
dialogInstance = new Dialog(this);
}
// ...