Switching Screens: Utilizing the Stacked Widget
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- ``Screen Transition``: Learn how to switch between multiple screens using the Stacked Widget.

- In PyQt, the ``QStackedWidget`` allows for the display of one screen (or page) at a time out of multiple available screens.
- In this example, three pages are added to the ``QStackedWidget``. Each page contains a button, enabling a switch to a different page.



.. code-block:: python
    :caption: scripts/PYQT2/03_toggle_screens/main.py
    :linenos:

    # -*- coding: utf-8 -*-

    import sys
    from PyQt5.QtWidgets import QApplication, QMainWindow, QPushButton, QVBoxLayout, QWidget, QStackedWidget, QLabel

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

            # Create the stacked widget
            self.stack = QStackedWidget()

            # Create some sample pages
            self.page1 = QWidget()
            self.page2 = QWidget()
            self.page3 = QWidget()

            # Add pages to the stacked widget
            self.stack.addWidget(self.page1)
            self.stack.addWidget(self.page2)
            self.stack.addWidget(self.page3)

            # Sample layout for page 1
            layout1 = QVBoxLayout(self.page1)
            layout1.addWidget(QLabel("여긴 1 페이지입니다."))
            button1 = QPushButton("2 페이지로 가자")
            layout1.addWidget(button1)
            button1.clicked.connect(self.go_to_page2)

            # Sample layout for page 2
            layout2 = QVBoxLayout(self.page2)
            layout2.addWidget(QLabel("여긴 2 페이지라고라"))
            button2 = QPushButton("3 페이지로 가기")
            layout2.addWidget(button2)
            button2.clicked.connect(self.go_to_page3)

            # Sample layout for page 3
            layout3 = QVBoxLayout(self.page3)
            layout3.addWidget(QLabel("여긴 3 페이지라고하지"))
            button3 = QPushButton("1 페이지로 가볼까")
            layout3.addWidget(button3)
            button3.clicked.connect(self.go_to_page1)

            # Set the current widget to be page 1
            self.stack.setCurrentWidget(self.page1)

            # Set the stacked widget as the central widget of the window
            self.setCentralWidget(self.stack)

        def go_to_page1(self):
            self.stack.setCurrentWidget(self.page1)

        def go_to_page2(self):
            self.stack.setCurrentWidget(self.page2)

        def go_to_page3(self):
            self.stack.setCurrentWidget(self.page3)

    if __name__ == '__main__':
        app = QApplication(sys.argv)
        mainWin = MainWindow()
        mainWin.show()
        sys.exit(app.exec_())

- By clicking the button, the ``clicked.connect()`` method is utilized to execute the connected slot function. Within that function, the ``setCurrentWidget()`` method is used to change the current screen.

- ``QStackedWidget``: A widget that contains multiple pages and displays only one at a time.

- ``setCurrentWidget()``: A method in ``QStackedWidget`` to set the currently displayed page.

Detailed Analysis
~~~~~~~~~~~~~~~~~~~

1. Creating the stacked widget:

   .. code-block:: python

      self.stack = QStackedWidget()

2. Creating and adding sample pages:

   .. code-block:: python

      self.page1 = QWidget()
      ...
      self.stack.addWidget(self.page1)

3. Setting content for each page: Each page contains a label and a button. Clicking the button will switch to a different page.
   
   .. code-block:: python

      layout1 = QVBoxLayout(self.page1)
      ...
      button1 = QPushButton("Go to page 2")

4. Connecting button click events: Use methods like ``go_to_page2`` to connect each button to the logic that switches to the respective page.
   
   .. code-block:: python

      button1.clicked.connect(self.go_to_page2)

5. Setting the initial page: This sets which page will be displayed by default when the app runs.
   
   .. code-block:: python

      self.stack.setCurrentWidget(self.page1)