PySide6 QMainWindow Tutorial: Build Your First Main Window

 

The QMainWindow class in PySide6 provides a main application window that includes standard features like a menu bar, toolbars, a status bar, and dock widgets. It serves as the foundation for creating complex GUI applications with a well-structured layout.

Key Features of QMainWindow

1. Menu Bar: Provides a menu bar for adding menus and actions.
2. Toolbars: Supports adding multiple toolbars for quick access to actions.
3. Status Bar: Includes a status bar for displaying status information.
4. Central Widget: Contains a central widget, which is the main content area of the window.
5. Dock Widgets: Allows adding dockable widgets that can be moved and resized.

Creating a Basic QMainWindow

To create a QMainWindow, subclass the QMainWindow class and add components like a central widget, menu bar, toolbars, and status bar. Here's a basic example:

from PySide6.QtGui import QAction
from PySide6.QtWidgets import QApplication, QMainWindow, QTextEdit, QToolBar, QStatusBar

class MainWindow(QMainWindow):
    def __init__(self):
        super().__init__()

        self.setWindowTitle('QMainWindow Example')
        self.setMinimumSize(600, 400)

        # Set the central widget
        self.text_edit = QTextEdit()
        self.setCentralWidget(self.text_edit)

        # Create the menu bar
        menu_bar = self.menuBar()
        file_menu = menu_bar.addMenu("File")

        # Add actions to the file menu
        new_action = QAction("New", self)
        open_action = QAction("Open", self)
        save_action = QAction("Save", self)
        exit_action = QAction("Exit", self)
        exit_action.triggered.connect(self.close)

        file_menu.addAction(new_action)
        file_menu.addAction(open_action)
        file_menu.addAction(save_action)
        file_menu.addAction(exit_action)

        # Create the toolbar
        toolbar = QToolBar("Main Toolbar")
        self.addToolBar(toolbar)
        toolbar.addAction(new_action)
        toolbar.addAction(open_action)
        toolbar.addAction(save_action)

        # Create the status bar
        status_bar = QStatusBar()
        self.setStatusBar(status_bar)
        status_bar.showMessage("Ready")

app = QApplication([])
app.setStyle("Fusion")
window = MainWindow()
window.show()
app.exec()

In this example, a QMainWindow is created with a central QTextEdit widget, a menu bar with file operations, a toolbar with actions, and a status bar.

Adding a Dock Widget

QMainWindow supports dock widgets, which can be moved around and docked in different areas of the window. Here's how to add a dock widget:

from PySide6.QtCore import Qt
from PySide6.QtGui import QAction
from PySide6.QtWidgets import QApplication, QMainWindow, QTextEdit, QToolBar, QStatusBar, QDockWidget, QListWidget

class MainWindow(QMainWindow):
    def __init__(self):
        super().__init__()

        self.setWindowTitle('QMainWindow Example')
        self.setMinimumSize(600, 400)

        # Set the central widget
        self.text_edit = QTextEdit()
        self.setCentralWidget(self.text_edit)

        # Create the menu bar
        menu_bar = self.menuBar()
        file_menu = menu_bar.addMenu("File")

        # Add actions to the file menu
        new_action = QAction("New", self)
        open_action = QAction("Open", self)
        save_action = QAction("Save", self)
        exit_action = QAction("Exit", self)
        exit_action.triggered.connect(self.close)

        file_menu.addAction(new_action)
        file_menu.addAction(open_action)
        file_menu.addAction(save_action)
        file_menu.addAction(exit_action)

        # Create the toolbar
        toolbar = QToolBar("Main Toolbar")
        self.addToolBar(toolbar)
        toolbar.addAction(new_action)
        toolbar.addAction(open_action)
        toolbar.addAction(save_action)

        # Create the status bar
        status_bar = QStatusBar()
        self.setStatusBar(status_bar)
        status_bar.showMessage("Ready")

        # Dock widget
        dock = QDockWidget("Dockable", self)
        self.addDockWidget(Qt.DockWidgetArea.RightDockWidgetArea, dock)

        list_widget = QListWidget()
        list_widget.addItems(["Item 1", "Item 2", "Item 3"])
        dock.setWidget(list_widget)

app = QApplication([])
app.setStyle("Fusion")
window = MainWindow()
window.show()
app.exec()

In this example, a dock widget containing a QListWidget is added to the right side of the QMainWindow.

Practical Example

Let's create a more practical example where QMainWindow is used to build a simple text editor with a menu bar, toolbar, status bar, and dock widget:

from PySide6.QtCore import Qt
from PySide6.QtGui import QAction
from PySide6.QtWidgets import (
    QApplication,
    QMainWindow,
    QTextEdit,
    QToolBar,
    QStatusBar,
    QDockWidget,
    QListWidget,
    QFileDialog)

class TextEditor(QMainWindow):
    def __init__(self):
        super().__init__()

        self.setWindowTitle('Simple Text Editor')
        self.setMinimumSize(800, 600)

        self.text_edit = QTextEdit()
        self.setCentralWidget(self.text_edit)

        # Menu bar
        menu_bar = self.menuBar()
        file_menu = menu_bar.addMenu("File")

        # Add actions to the file menu
        new_action = QAction("New", self)
        open_action = QAction("Open", self)
        save_action = QAction("Save", self)
        exit_action = QAction("Exit", self)
        exit_action.triggered.connect(self.close)

        new_action.triggered.connect(self.new_file)
        open_action.triggered.connect(self.open_file)
        save_action.triggered.connect(self.save_file)

        file_menu.addAction(new_action)
        file_menu.addAction(open_action)
        file_menu.addAction(save_action)
        file_menu.addAction(exit_action)

        # Toolbar
        toolbar = QToolBar("Main Toolbar")
        self.addToolBar(toolbar)
        toolbar.addAction(new_action)
        toolbar.addAction(open_action)
        toolbar.addAction(save_action)

        # Status bar
        status_bar = QStatusBar()
        self.setStatusBar(status_bar)
        status_bar.showMessage("Ready")

        # Dock widget
        dock = QDockWidget("Dockable", self)
        self.addDockWidget(Qt.DockWidgetArea.RightDockWidgetArea, dock)

        list_widget = QListWidget()
        list_widget.addItems(["Item 1", "Item 2", "Item 3"])
        dock.setWidget(list_widget)

    def new_file(self):
        self.text_edit.clear()

    def open_file(self):
        file_name, _ = QFileDialog.getOpenFileName(self, "Open File", "", "Text Files (*.txt);;All Files (*)")
        if file_name:
            with open(file_name, 'r') as file:
                self.text_edit.setText(file.read())

    def save_file(self):
        file_name, _ = QFileDialog.getSaveFileName(self, "Save File", "", "Text Files (*.txt);;All Files (*)")
        if file_name:
            with open(file_name, 'w') as file:
                file.write(self.text_edit.toPlainText())

app = QApplication([])
window = TextEditor()
window.show()
app.exec()
 

In this example, we create a simple text editor with basic file operations like new, open, and save. The QMainWindow includes a menu bar, toolbar, status bar, and a dockable list widget.