使用工具栏更新pyqt5 gui中的嵌入式matplotlib图

Question

In this post I asked how to embed a matplotlib plot in a pyqt5 gui which is working fine now. Now I have a further problem that I couldn't solve until now: how can I update the figure?

I tried to update the canvas by calling

self.plotWidget = FigureCanvas(fig)

every time with a new "fig" object but nothing happened. So I tried to add it to the layout

self.lay.addWidget(self.plotWidget)

but this adds another subplot to the widget. I guess that I have to clear the previous plot before updating but I don't know how to do it.

What is the correct strategy to replot using the update method?

Thanks!

# -*- coding: utf-8 -*-

import sys
import numpy as np   

from PyQt5 import QtCore, QtWidgets, uic

import matplotlib
matplotlib.use('QT5Agg')

import matplotlib.pylab as plt

from matplotlib.backends.qt_compat import QtCore, QtWidgets, is_pyqt5
from matplotlib.backends.backend_qt5agg import FigureCanvas, NavigationToolbar2QT as NavigationToolbar
from matplotlib.figure import Figure

class MyWindow(QMainWindow):

    def __init__(self):

        super(MyWindow, self).__init__()
        uic.loadUi('test.ui', self) 

        # test data
        data = np.array([0.7,0.7,0.7,0.8,0.9,0.9,1.5,1.5,1.5,1.5])        
        fig, ax1 = plt.subplots()
        bins = np.arange(0.6, 1.62, 0.02)
        n1, bins1, patches1 = ax1.hist(data, bins, alpha=0.6, density=False, cumulative=False)

        # plot
        self.plotWidget = FigureCanvas(fig)
        self.lay = QtWidgets.QVBoxLayout(self.content_plot)  
        self.lay.setContentsMargins(0, 0, 0, 0)      
        self.lay.addWidget(self.plotWidget)

        # add toolbar
        self.addToolBar(QtCore.Qt.BottomToolBarArea, NavigationToolbar(self.plotWidget, self))        

        # button event
        self.pushButton.clicked.connect(self.update)

        # show window
        self.show() 

        #########################################

    def update(self):

        data = np.array([0.1,0.1,0.1,0.1,0.3,0.3,1.7,1.7,1.7,1.7])        
        fig, ax1 = plt.subplots()
        bins = np.arange(0.6, 1.62, 0.02)
        n1, bins1, patches1 = ax1.hist(data, bins, alpha=0.6, density=False, cumulative=False)

        # show plot in canvas  
        self.plotWidget = FigureCanvas(fig)
        self.toolbarWidget = NavigationToolbar(self.plotWidget, self)        


if __name__ == '__main__':

    app = QtWidgets.QApplication(sys.argv)
    window = MyWindow()
    sys.exit(app.exec_())

Answer 1

You should not create a new figure, instead, reuse the axes that you already have. That means that you have to keep a reference to that object first.

I cannot test the code right now, but you should do something like

def __init__(self):
    (...)
    self.fig, self.ax = plt.subplots()
    (...)

def update(self):
    data = (...)
    self.ax.cla()  # clear the axes content
    self.ax.hist(...)
    self.fig.canvas.draw_idle()  # actually draw the new content