如何让PyQt5中的小部件填满屏幕？

import sys
from PyQt5.QtWidgets import QApplication, QMainWindow, QWidget, QVBoxLayout

app = QApplication(sys.argv)
screen = app.primaryScreen()
screen_size = screen.availableGeometry()

window = QMainWindow()
window.resize(screen_size.width(), screen_size.height())

central_widget = QWidget(window)
layout = QVBoxLayout(central_widget)

# 示例：创建一个填满屏幕的按钮
from PyQt5.QtWidgets import QPushButton

button = QPushButton("Fill Screen")
layout.addWidget(button)

window.setCentralWidget(central_widget)

window.show()
sys.exit(app.exec_())