为什么4个按钮不显示？

Question

#task is to create 4 buttons using the Canvas module in Tkinter
class Buttons:
    def __init__(self, par2, par3, par4, par5, fill, xpos, ypos):
        self.par2 = par2
        self.par3 = par3
        self.par4 = par4
        self.par5 = par5
        self.fill = fill
        self.xpos = xpos
        self.ypos = ypos

    def display_button(self):
        canvas.create_oval(self.par2, self.par3, self.par4, self.par5, fill=str(self.fill))
        canvas.place(self.xpos, self.ypos)

#create the buttons using the parameters in def __init__
button1 = Buttons(100, 100, 300, 300, "grey", -25, 25)
button2 = Buttons(100, 100, 300, 300, "grey", 0, 0)
button3 = Buttons(100, 100, 300, 300, "grey", 100, 25)
button4 = Buttons(100, 100, 300, 300, "grey", 50, 50)

The window and canvas have already been created previously and work fine. Could someone tell me why nothing appears in the window when I run the program? Thanks

Answer 1

It looks like you're not invoking the Buttons.display_button method on your button instances. Unless you do that, you can expect to see nothing.

From the way your code is written, it looks like canvas is a global tk.Canvas object. Anytime you invoke Buttons.display_button , you are also calling canvas.place , which is meant to be used as an alternative to canvas.pack - are you sure that's what you want to do? Because, that doesn't seem right.

I would start with something simpler (something that works) and go from there. A couple of other suggestions: I don't think Buttons is a good name for the class, since an instance of that class should represent a single button - Button is a better name, I think.

Also, the method name display_button is a bit redundant. We already know that this method "displays" a button by virtue of the fact that it's part of the Button class - I would call it something like display or render .

import tkinter as tk

root = tk.Tk()

canvas = tk.Canvas(root, width=200, height=200)
canvas.pack()

class Button:

    def __init__(self, *args, **kwargs):
        self.args = args
        self.kwargs = kwargs

    def render(self):
        canvas.create_oval(*self.args, **self.kwargs)

button = Button(50, 50, 150, 150, fill="grey")
button.render()

root.mainloop()