**Course Title:** Qt 6 Application Development with C++ **Section Title:** Widgets, Layouts, and Events **Topic:** Introduction to basic Qt widgets: QPushButton, QLabel, QLineEdit, etc. **Introduction** In this topic, we will explore the fundamental widgets in Qt, which are the building blocks of graphical user interfaces (GUIs). These widgets enable you to create interactive and user-friendly applications. We will cover the basic usage, properties, and signal-slot connections of QPushButton, QLabel, QLineEdit, and more. By the end of this topic, you will be able to create a simple GUI application using these widgets. **QPushButton** QPushButton is a widget that allows users to perform a specific action when clicked. It is one of the most commonly used widgets in Qt applications. Here's a simple example of creating a QPushButton: ```cpp QPushButton* button = new QPushButton("Click me!", this); ``` In this example, "Click me!" is the text displayed on the button, and `this` is the parent widget. You can connect a slot to the button's `clicked` signal to perform an action when the button is clicked: ```cpp connect(button, &QPushButton::clicked, [] { qDebug() << "Button clicked!"; }); ``` This will print "Button clicked!" to the console when the button is clicked. **QLabel** QLabel is a widget that displays text or an image. It is often used to display information or provide feedback to the user. Here's a simple example of creating a QLabel: ```cpp QLabel* label = new QLabel("Hello, world!", this); ``` You can set the text of the label using the `setText` method: ```cpp label->setText("New text!"); ``` **QLineEdit** QLineEdit is a widget that allows the user to enter a single line of text. It is often used to input data such as names, passwords, or search queries. Here's a simple example of creating a QLineEdit: ```cpp QLineEdit* lineEdit = new QLineEdit(this); ``` You can retrieve the text entered by the user using the `text` method: ```cpp QString text = lineEdit->text(); ``` **QComboBox** QComboBox is a widget that allows the user to select an item from a list. It is often used to select options or make choices. Here's a simple example of creating a QComboBox: ```cpp QComboBox* comboBox = new QComboBox(this); comboBox->addItem("Option 1"); comboBox->addItem("Option 2"); ``` You can retrieve the selected item using the `currentText` method: ```cpp QString selectedText = comboBox->currentText(); ``` **QCheckBox** QCheckBox is a widget that allows the user to select or deselect an option. It is often used to enable or disable features. Here's a simple example of creating a QCheckBox: ```cpp QCheckBox* checkBox = new QCheckBox("Option", this); ``` You can retrieve the checked state using the `isChecked` method: ```cpp bool isChecked = checkBox->isChecked(); ``` **Key Concepts** * Widgets are the building blocks of GUI applications. * QPushButton, QLabel, QLineEdit, QComboBox, and QCheckBox are some of the most commonly used widgets in Qt applications. * Signals and slots are used to connect widgets to each other and perform actions. **Practical Takeaways** * Use QPushButton to create interactive buttons. * Use QLabel to display information or provide feedback to the user. * Use QLineEdit to input single lines of text. * Use QComboBox to select items from a list. * Use QCheckBox to enable or disable options. **Example Application** Here's an example of a simple GUI application that uses some of the widgets covered in this topic: ```cpp #include <QApplication> #include <QPushButton> #include <QLabel> #include <QLineEdit> #include <QComboBox> #include <QCheckBox> int main(int argc, char* argv[]) { QApplication app(argc, argv); QWidget* window = new QWidget; window->setWindowTitle("Widgets Example"); QPushButton* button = new QPushButton("Click me!", window); QLabel* label = new QLabel("Hello, world!", window); QLineEdit* lineEdit = new QLineEdit(window); QComboBox* comboBox = new QComboBox(window); QComboBox->addItem("Option 1"); QComboBox->addItem("Option 2"); QCheckBox* checkBox = new QCheckBox("Option", window); // Layout and show the window // ... return app.exec(); } ``` This example demonstrates how to create a simple GUI application using Qt widgets. **External Resources** For more information on Qt widgets, visit the official Qt documentation: [https://doc.qt.io/qt-6/](https://doc.qt.io/qt-6/) **Leave a comment or ask for help** If you have any questions or need further clarification on any of the topics covered, please leave a comment below. I'll be happy to help. In the next topic, we will cover working with layouts in Qt, including QVBoxLayout, QHBoxLayout, and QGridLayout.