在PYQT5中QscrollArea(滚动条)如何使用

import sys
from PyQt5.QtWidgets import *
 
 
class MainWindow(QMainWindow):
 def __init__(self,):
  super(QMainWindow,self).__init__()
  self.number = 0
 
  w = QWidget()
  self.setCentralWidget(w)
 
  self.topFiller = QWidget()
  self.topFiller.setMinimumSize(250, 2000)#######设置滚动条的尺寸
  for filename in range(20):
   self.MapButton = QPushButton(self.topFiller)
   self.MapButton.setText(str(filename))
   self.MapButton.move(10,filename*40)
  ##创建一个滚动条
  self.scroll = QScrollArea()
  self.scroll.setWidget(self.topFiller)
 
 
  self.vbox = QVBoxLayout()
  self.vbox.addWidget(self.scroll)
  w.setLayout(self.vbox)
 
  self.statusBar().showMessage("底部信息栏")
  self.resize(300, 500)
 
if __name__ == "__main__":
 app = QApplication(sys.argv)
 mainwindow = MainWindow()
 mainwindow.show()
 sys.exit(app.exec_())