Matplotlib- PyQt5中的图形在运行时不更新

import sys
from PyQt5.QtWidgets import QApplication, QMainWindow, QVBoxLayout, QSizePolicy, QWidget
from matplotlib.figure import Figure
from matplotlib.backends.backend_qt5agg import FigureCanvasQTAgg as FigureCanvas
import numpy as np
import random

class MyMplCanvas(FigureCanvas):
    def __init__(self, parent=None, width=5, height=4, dpi=100):
        fig = Figure(figsize=(width, height), dpi=dpi)
        self.axes = fig.add_subplot(111)

        FigureCanvas.__init__(self, fig)
        self.setParent(parent)

        FigureCanvas.setSizePolicy(self, QSizePolicy.Expanding, QSizePolicy.Expanding)
        FigureCanvas.updateGeometry(self)

    def plot(self):
        data = [random.random() for i in range(25)]
        self.axes.plot(data, 'r')
        self.draw()

class ApplicationWindow(QMainWindow):
    def __init__(self):
        QMainWindow.__init__(self)
        self.main_widget = QWidget(self)

        layout = QVBoxLayout(self.main_widget)
        self.canvas = MyMplCanvas(self.main_widget, width=5, height=4, dpi=100)
        layout.addWidget(self.canvas)

        self.main_widget.setFocus()
        self.setCentralWidget(self.main_widget)

if __name__ == '__main__':
    app = QApplication(sys.argv)

    window = ApplicationWindow()
    window.setWindowTitle("Matplotlib in PyQt5")
    window.show()

    # Update the plot every second
    timer = QtCore.QTimer()
    timer.timeout.connect(window.canvas.plot)
    timer.start(1000)

    sys.exit(app.exec_())