Correct use of setWindowTitle for QWidget object

[Swati777999]

Hi All,

I am struggling to correctly use the predefined functions and properties in different classes of Qt.

I want to set title for my QWidget object but I am unable to do so with setWindowTitle().
I am sharing my code below, please let me know why the function setWindowTitle does not work in this case.

mainwindow.h

 #ifndef MAINWINDOW_H
 #define MAINWINDOW_H
 #include <QMainWindow>
 #include <QPushButton>
 #include <QVBoxLayout>
 #include <QHBoxLayout>
 #include<QString>

QT_BEGIN_NAMESPACE
namespace Ui { class MainWindow; }
QT_END_NAMESPACE
class MainWindow : public QMainWindow
{
Q_OBJECT
public:
MainWindow(QWidget *parent = nullptr);
~MainWindow();
void setWindowTitle(const QString &title);
 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);
QWidget *window = new QWidget; // widget object
window->windowTitle();
   //Creating button objects
   QPushButton *button1 = new QPushButton("One");
   QPushButton *button2 = new QPushButton("Two");
   QPushButton *button3 = new QPushButton("Three");
   QPushButton *button4 = new QPushButton("Four");
   QPushButton *button5 = new QPushButton("Five");

   //Creating vertical layout for buttons
  // QVBoxLayout *layout = new QVBoxLayout(window);

   //creating horizontal layout for buttons
   QHBoxLayout *layout = new QHBoxLayout(window);

   layout->addWidget(button1);
   layout->addWidget(button2);
   layout->addWidget(button3);
   layout->addWidget(button4);
   layout->addWidget(button5);

   window->show();
   }

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

 void MainWindow::setWindowTitle(const QString &title)
 {
 QString win_title="Experimenting with Layouts;Vertical and horizontal";
 }

The title of the widget does not change .

[JKSH]

@Swati777999 said in Correct use of setWindowTitle for QWidget object:

 void MainWindow::setWindowTitle(const QString &title)
 {
 QString win_title="Experimenting with Layouts;Vertical and horizontal";
 }

Call QWidget's implementation of setWindowTitle(). Don't implement your own.

Remove MainWindow::setWindowTitle() from mainwindow.h and mainwindow.cpp. Then, call this in your constructor: this->setWindowTitle("New title");

[Swati777999]

@JKSH It worked for me. I just added the following in the constructor
this ->setWindowTitle("Experimenting with the layouts");

and removed the definition of setWindowTitle.

I can use window->setWindowTitle(" " ) for setting the title of the widget window.

Just bear with me as I am an absolute beginner in Qt.

Thanks for your help!

[Swati777999]

@JKSH

So to summarise the learning point here; To use the object of MainWindow class in the constructor of MainWindow in mainWindow.cpp file, use ‘this’ as the object of the MainWindow instead of ‘parent’
To use the member function;
this -> member_function()

Just want to be confirmed at this point, members of any class can be accessed by dot operator, right?

[JKSH]

@Swati777999 said in Correct use of setWindowTitle for QWidget object:

So to summarise the learning point here; To use the object of MainWindow class in the constructor of MainWindow in mainWindow.cpp file, use ‘this’ as the object of the MainWindow instead of ‘parent’
To use the member function;
this -> member_function()

Yes.

Note also that this is implied. The 2 calls to member_function() below do exactly the same thing:

void MyClass::func() {
    this->member_function(); // 1st call
    member_function(); // 2nd call
}

Just want to be confirmed at this point, members of any class can be accessed by dot operator, right?

Yes, unless you have a pointer to the object. For pointers, you use -> not .

Note: this is a pointer