python - 在 Tkinter 中更新 Canvas

Question

有人知道如何修改以下代码，以便每次更改测角函数时都会更新图形吗？绘图是在函数 plot() 中完成的。 stackoverflow 上有一些相关线程，但我无法将它们应用到我的示例代码中...

非常感谢，

麦基

import numpy as np
import Tkinter as tk
from matplotlib.figure import Figure
from matplotlib.backends.backend_tkagg import FigureCanvasTkAgg

class App:

    def __init__(self, window):

        self.window = window

        # set up pi
        pi = 3.141592654

        # create the frame and pack to the object
        frame = tk.Frame(window)
        frame.pack()

        def callback(func, *pargs):
            print(func.get())
            func.set(func.get())
            self.plot()
            self.window.update()

        self.func = tk.StringVar()
        self.func.set("sin") # default value
        self.func.trace('w', lambda *pargs: callback(self.func, *pargs))

        self.button = tk.OptionMenu(window, self.func, "sin", "cos", "tan")
        self.button.pack(side = tk.TOP)

        self.min_value = tk.Entry(window, justify = tk.RIGHT)
        self.min_value.pack()

        self.min_value.delete(0, tk.END)
        self.min_value.insert(0, -pi)

        self.max_value = tk.Entry(window, justify = tk.RIGHT)
        self.max_value.pack()

        self.max_value.delete(0, tk.END)
        self.max_value.insert(0, pi)

        self.button = tk.Button(frame, text = "QUIT", foreground = "red", command = frame.quit)
        self.button.pack(side = tk.BOTTOM)

        self.draw = tk.Button(frame, text = "DRAW", command = self.plot())
        self.draw.pack(side = tk.LEFT)

    def plot(self):

        # generate numbers for the plot
        x = np.array(np.arange(np.float64(self.min_value.get()), np.float64(self.max_value.get()), 0.001))

        if self.func.get() == 'sin':
            print('plotting sin()')
            y = np.sin(x)
        elif self.func.get() == 'cos':
            print('plotting cos()')
            y = np.cos(x)
        else:
            print('plotting tan()')
            y = np.tan(x)

        # create the plot
        fig = Figure(figsize = (6, 6))
        a = fig.add_subplot(1,1,1)
        a.plot(x, y, color = 'blue')
        a.set_title ("Goniometric Functions", fontsize = 12)
        a.set_ylabel(self.func.get() + '(x)', fontsize = 8)
        a.set_xlabel('x', fontsize = 8)

        # canvas
        canvas = FigureCanvasTkAgg(fig, master = self.window)
        self.widget = canvas.get_tk_widget().pack()
        print('here I should update canvas')
        canvas.draw()

root = tk.Tk()
app = App(root)   
root.mainloop()
root.destroy()

Answer 1

您应该在 Canvas 上创建空图，然后仅使用 a.set_xdata()、a.set_ydata() 替换图中的数据

import numpy as np
import tkinter as tk
from matplotlib.figure import Figure
from matplotlib.backends.backend_tkagg import FigureCanvasTkAgg

class App:

    def __init__(self, window):

        self.window = window

        # set up pi
        pi = 3.141592654

        # create the frame and pack to the object
        frame = tk.Frame(window)
        frame.pack()

        def callback(func, *pargs):
            print(func.get())
            #func.set(func.get()) # <-- it has no sense
            self.update_plot()
            self.window.update()

        self.func = tk.StringVar()
        self.func.set("sin") # default value
        self.func.trace('w', lambda *pargs: callback(self.func, *pargs))

        self.button = tk.OptionMenu(window, self.func, "sin", "cos", "tan")
        self.button.pack(side = tk.TOP)

        self.min_value = tk.Entry(window, justify = tk.RIGHT)
        self.min_value.pack()

        self.min_value.delete(0, tk.END)
        self.min_value.insert(0, -pi)

        self.max_value = tk.Entry(window, justify=tk.RIGHT)
        self.max_value.pack()

        self.max_value.delete(0, tk.END)
        self.max_value.insert(0, pi)

        self.button = tk.Button(frame, text="QUIT", foreground="red", command=root.destroy) #<--
        self.button.pack(side = tk.BOTTOM)

        self.draw = tk.Button(frame, text="DRAW", command=self.update_plot)
        self.draw.pack(side = tk.LEFT)

        # create empty plot
        self.create_plot()
        # update plot with current function at start
        self.update_plot()

    def create_plot(self):

        # create the plot
        self.fig = Figure(figsize = (6, 6))
        self.a = self.fig.add_subplot(1,1,1)

        self.p, _ = self.a.plot([], [], color = 'blue')

        self.a.set_title ("Goniometric Functions", fontsize = 12)

        # canvas
        self.canvas = FigureCanvasTkAgg(self.fig, master = self.window)
        self.widget = self.canvas.get_tk_widget().pack()
        #self.canvas.draw()

    def update_plot(self):
        print('update')

        # generate numbers for the plot
        x = np.array(np.arange(np.float64(self.min_value.get()), np.float64(self.max_value.get()), 0.001))

        if self.func.get() == 'sin':
            print('plotting sin()')
            y = np.sin(x)
        elif self.func.get() == 'cos':
            print('plotting cos()')
            y = np.cos(x)
        else:
            print('plotting tan()')
            y = np.tan(x)

        # replace labels
        self.a.set_ylabel(self.func.get() + '(x)', fontsize = 8)
        self.a.set_xlabel('x', fontsize = 8)

        # replace data
        self.p.set_xdata(x)
        self.p.set_ydata(y)

        # rescale
        self.a.relim()
        self.a.autoscale_view()

        # update screen
        self.canvas.draw()

root = tk.Tk()
app = App(root)   
root.mainloop()
#root.destroy() You don't need it