如何将QLineEdit() & QPushButton带到登录窗口的中心？

import sys
from PyQt5.QtWidgets import QApplication, QWidget, QVBoxLayout, QLineEdit, QPushButton

class LoginWindow(QWidget):
    def __init__(self):
        super().__init__()
        self.initUI()

    def initUI(self):
        # 创建QLineEdit和QPushButton
        lineEdit = QLineEdit()
        pushButton = QPushButton("登录")

        # 创建垂直布局管理器
        layout = QVBoxLayout()
        layout.addWidget(lineEdit)
        layout.addWidget(pushButton)

        # 设置布局管理器为窗口的中心布局
        self.setLayout(layout)

        self.setWindowTitle("登录窗口")
        self.setGeometry(300, 300, 300, 200)
        self.show()

if __name__ == '__main__':
    app = QApplication(sys.argv)
    loginWindow = LoginWindow()
    sys.exit(app.exec_())