Matplotlib图在Tkinter GUI中停止更新

Question

I'm working on this application which involves plotting a line or circle on an empty plot after pressing a button. It was all well until suddenly, the graph just stopped updating. For example:

import math
import tkinter as tk
from tkinter import *

import matplotlib
import matplotlib.pyplot as plt
from numpy import arange, sin, cos, tan, pi
from matplotlib.backends.backend_tkagg import FigureCanvasTkAgg, 
NavigationToolbar2TkAgg
from matplotlib.backend_bases import key_press_handler
from matplotlib.figure import Figure
from matplotlib.patches import Circle
# Initialising the graph
f = Figure(figsize=(6, 6), dpi=100)
a = f.add_subplot(111)

root = tk.Tk()

class Application(tk.Frame):
  def __init__(self, master=None):
    super().__init__(master)
    self.pack()
    self.mainwindow()

  def mainwindow(self):
    self.add_loci = Button(self)
    self.add_loci["text"] = "Add Line"
    self.add_loci["command"] = self.line
    self.add_loci.pack(side = TOP)

    # Plotting an empty graph
    a.set_xlabel('Re')
    a.set_ylabel('Im')
    a.grid(b=None)
    a.plot(0, 0)
    # Setting up and showing the toolbar and the graph
    canvas = FigureCanvasTkAgg(f, master=root)
    canvas.show()
    canvas.get_tk_widget().pack(side = BOTTOM, fill=BOTH, expand=1)
    toolbar = NavigationToolbar2TkAgg(canvas, root)
    toolbar.update()
    canvas._tkcanvas.pack(side = BOTTOM, fill=BOTH, expand=1)

  def line(self):
    a.plot([0, 10], [0, 10])
    print('test')

app = Application(master=root)
app.mainloop()

The supposed outcome when pressing the button is that a straight should appear, but it doesn't. I added the print statement to check if the button is working correctly and it does, so I really don't know what the problem here is. I'm currently using Spyder (3.2.4).

Answer 1

Everything is working, ie the line is being plotted, however the figure needs to be updated. You can do this using figure.canvas.draw() after your plot. Your code would look something like:

f = Figure(figsize=(6, 6), dpi=100)
a = f.add_subplot(111)

root = tk.Tk()

class Application(tk.Frame):
    def __init__(self, master=None):
        super().__init__(master)
        self.pack()
        self.mainwindow()

    def mainwindow(self):
        self.add_loci = Button(self)
        self.add_loci["text"] = "Add Line"
        self.add_loci["command"] = self.line
        self.add_loci.pack(side = TOP)

        # Plotting an empty graph
        a.set_xlabel('Re')
        a.set_ylabel('Im')
        a.grid(b=None)
        a.plot(0, 0)
        # Setting up and showing the toolbar and the graph
        canvas = FigureCanvasTkAgg(f, master=root)
        canvas.show()
        canvas.get_tk_widget().pack(side = BOTTOM, fill=BOTH, expand=1)
        toolbar = NavigationToolbar2TkAgg(canvas, root)
        toolbar.update()
        canvas._tkcanvas.pack(side = BOTTOM, fill=BOTH, expand=1)

    def line(self):

        a.plot([0, 10], [0, 10])
        f.canvas.draw()

        print('test')

app = Application(master=root)
app.mainloop()

You could also make the canvas you create an instance variable, by using self.canvas = ... . Then using self.canvas.draw() . Your mainwindow and line function would then look like:

def mainwindow(self):
    self.add_loci = Button(self)
    self.add_loci["text"] = "Add Line"
    self.add_loci["command"] = self.line
    self.add_loci.pack(side = TOP)

    # Plotting an empty graph
    a.set_xlabel('Re')
    a.set_ylabel('Im')
    a.grid(b=None)
    a.plot(0, 0)
    # Setting up and showing the toolbar and the graph
    self.canvas = FigureCanvasTkAgg(f, master=root)
    self.canvas.show()
    self.canvas.get_tk_widget().pack(side = BOTTOM, fill=BOTH, expand=1)
    toolbar = NavigationToolbar2TkAgg(self.canvas, root)
    toolbar.update()
    self.canvas._tkcanvas.pack(side = BOTTOM, fill=BOTH, expand=1)

def line(self):

    a.plot([0, 10], [0, 10])
    self.canvas.draw()

    print('test')

Both would produce the same result.