pyqt5视频小部件未在布局中显示

import sys
from PyQt5.QtWidgets import QApplication, QWidget, QVBoxLayout, QPushButton, QMediaPlayer, QVideoWidget
from PyQt5.QtCore import QUrl

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

    def initUI(self):
        self.setGeometry(100, 100, 300, 200)  # 设置主窗口的位置和大小

        # 创建布局管理器
        layout = QVBoxLayout(self)

        # 创建视频小部件
        video_widget = QVideoWidget(self)
        layout.addWidget(video_widget)

        # 创建播放按钮
        play_button = QPushButton('Play', self)
        layout.addWidget(play_button)

        # 创建媒体播放器
        media_player = QMediaPlayer(self)
        media_player.setVideoOutput(video_widget)
        media_player.setMedia(QUrl.fromLocalFile('path/to/your/video/file.mp4'))

        # 连接播放按钮的点击事件
        play_button.clicked.connect(media_player.play)

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