unable to update matplotlib figure in pyqt5 - pyqt5

Question

I am studying MDIwindow in pyqt5
I want to update the ForcemapWidget figure when I click on the HeatmapWidget figure. However, the diagram did not update.
It is confirmed that the canvas in the ForcemapWidget is updated by the print function. We know that the coordinates are also obtained. But for some reason, the chart doesn't update.
import numpy as np
import matplotlib.pyplot as plt
from PyQt5.QtWidgets import QVBoxLayout,QApplication,QWidget,QMainWindow,QMdiArea,QAction,QMdiSubWindow,QTextEdit, \
QComboBox,QLineEdit,QPushButton,QCheckBox,QFormLayout
import sys
from matplotlib.backends.backend_qt5agg import FigureCanvasQTAgg as FigureCanvas
class MDIWindow(QMainWindow):
count=0
def __init__(self):
super ().__init__()
self.mdi=QMdiArea()
self.setCentralWidget(self.mdi)
bar=self.menuBar()
file=bar.addMenu("File")
file.addAction("New")
file.addAction("Cascade")
file.addAction("Tiled")
file.triggered[QAction].connect(self.tritri)
self.setWindowTitle("MDI Application")
# 最初のサブウィンドウを作成
sub=QMdiSubWindow()
form_widget=FormWidget()
sub.setWidget(form_widget)
sub.setWindowTitle("Sub Window 1")
self.mdi.addSubWindow(sub)
sub.show()
sub2=QMdiSubWindow()
# ForcemapWidget.force_update()
form_widget=ForcemapWidget()
# form_widget.update()
# print(form_widget)
sub2.setWidget (form_widget)
sub2.setWindowTitle("Sub Window 2")
self.mdi.addSubWindow(sub2)
sub2.show()
def tritri(self,p):
if p.text()=="New":
MDIWindow.count=MDIWindow.count+1
sub=QMdiSubWindow()
heatmap_widget=HeatmapWidget()
sub.setWidget(heatmap_widget)
sub.setWindowTitle("Sub Window"+str(MDIWindow.count))
self.mdi.addSubWindow(sub)
sub.show()
if p.text()=="Cascade":
self.mdi.cascadeSubWindows()
if p.text()=="Tiled":
self.mdi.tileSubWindows ()
class HeatmapWidget(QWidget):
def __init__(self):
super().__init__()
self.forcemapWidget=ForcemapWidget
fig,ax=plt.subplots (figsize = (1,1))
heatmap=np.random.rand (256,256)
im=ax.imshow(heatmap,cmap = "hot")
fig.colorbar(im)
ax.set_title("Heatmap")
fig.canvas.mpl_connect("button_press_event",self.onclick)
canvas=FigureCanvas(fig)
layout=QVBoxLayout()
layout.addWidget(canvas)
self.setLayout (layout)
def onclick(self,event):
x,y=event.xdata,event.ydata
forcemap=ForcemapWidget(x)
class ForcemapWidget (QWidget):
def __init__(self,x=None):
super().__init__()
self.figure=plt.figure()
self.initUI(x)
def initUI(self,x):
self.figure.clear()
ax=self.figure.add_subplot(111)
if x is not None:
heatmap=np.random.rand(int (x),256)
else:
heatmap=np.random.rand(256,256)
im=ax.imshow(heatmap,cmap = "hot")
# self.figure.colorbar (im)
canvas=FigureCanvas(self.figure)
layout=QVBoxLayout()
layout.addWidget(canvas)
self.setLayout(layout)
self.update()
class FormWidget(QWidget):
def __init__(self):
super().__init__()
form_layout = QFormLayout()
combo = QComboBox()
combo.addItems(["Option 1", "Option 2", "Option 3"])
form_layout.addRow("Dropdown:", combo)
line_edit = QLineEdit()
form_layout.addRow("Input:", line_edit)
button = QPushButton("Submit")
form_layout.addRow(button)
check_box = QCheckBox()
form_layout.addRow("Checkbox:", check_box)
self.setLayout(form_layout)
app = QApplication(sys.argv)
mdi = MDIWindow()
mdi.show()
app.exec_()