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python - tkinter：为什么不删除（“全部”）删除组合框和条目小部件？

问题描述

我的意思是整个小部件而不是里面的文本。我还试图在论坛上获得现有的解决方案。我已经剥离了代码以仅显示问题。

我的问题是......当我放置ComboBox和Entry小部件时canvas2，它们不会被删除canvas2.delete("all")。

如果您从菜单中选择“加权图”，然后选择“无向图”，则会出现问题。在“加权图”之后，ComboBox和Entry小部件仍然存在（其他所有内容都按预期删除）。我放了一个时间延迟和一些提示来显示问题。

from tkinter import *
from tkinter import ttk
import time

tk = Tk()
tk.geometry("970x660")
menubar = Menu(tk)
tk.config(menu=menubar)

wrapper1 = LabelFrame(tk, text="Display", height=500)
wrapper2 = LabelFrame(tk, text="Command", width=800)

# canvas was setup to be a vertically scrolling region, I have cut most of that code
# (but my problem does not lie with canvas, that's working fine)
canvas = Canvas(wrapper1, height=500)
canvas.pack(side=LEFT, fill="both", expand="yes")

myframe = Frame(canvas)
canvas.create_window((0,0), window=myframe, anchor="nw", height=500)

# Note: My problem lies on canvas2,
canvas2 = Canvas(wrapper2)
canvas2.pack(side=LEFT, fill="both", expand="yes")

canvas2.update()

wrapper1.pack(fill="both", expand="yes", padx=10, pady=0)
wrapper2.pack(fill="both", expand="yes", padx=10, pady=5)

def DoNothing():
    print("Doing nothing!")

def BinaryTree(Weighted, Mode):

    canvas.delete("all")
    print("Before canvas2.delete...")
    canvas2.delete("all")
    print("...after canvas2.delete... now waiting 3 seconds so you can inspect if canvas2 is CLEAR... ")
    print("...I would expect canvas2 to be clear but Combobox and Entry remain!... ")

    canvas2.update()
    tk.update()

    time.sleep(3)

    button1 = Button(canvas2, text = "Add Node",  command= lambda: DoNothing(), width=13, anchor=W)
    button1_window = canvas2.create_window(20, 40, anchor=W, window=button1)

    entry1 = Entry(canvas2, width=10)
    entry1.place(x=150, y=40, anchor=W)

    button2 = Button(canvas2, text = "Add Edge",  command= lambda: DoNothing(), width=13, anchor=W)
    button2_window = canvas2.create_window(20, 80, anchor=W, window=button2)

    cb1 = ttk.Combobox(canvas2, values=DoNothing(), postcommand=lambda: DoNothing(), width=13, state="readonly")
    cb1.place(x=150, y=80, anchor=W)

    cb2 = ttk.Combobox(canvas2, values=DoNothing(), postcommand=lambda: DoNothing(), width=13, state="readonly")
    cb2.place(x=260, y=80, anchor=W)

    if Weighted == True:
        canvas2.create_text(380, 80, text="Weight:", anchor=W)
        entry2 = Entry(canvas2, width=4)
        entry2.place(x=429, y=80, anchor=W)

    button3 = Button(canvas2, text = "Delete All Nodes",  command= lambda: DoNothing(), width=13, anchor=W)
    button3_window = canvas2.create_window(420, 40, anchor=W, window=button3)

    canvas2.update()
    tk.update()

lmenu = Menu(menubar)
menubar.add_cascade(label="Learning Menu", menu=lmenu)

lmenu.add_command(label="Weighted Graph", command= lambda: BinaryTree(True, "DirectedGraph"))
lmenu.add_command(label="Undirected Graph", command= lambda: BinaryTree(False, "UndirectedGraph"))


while True:
    tk.update_idletasks()
    tk.update()
    time.sleep(0.01)

标签： pythontkinter

解决方案

为什么 delete(“all”) 不能删除 Combobox 和 Entry 小部件？

这就是 tkinter 的工作原理。canvasdelete方法只删除画布对象。这意味着，在画布上创建的对象使用“创建”函数（create_rectangle、、create_window等）。对于窗口对象，该delete方法将删除创建的画布对象，create_window但并非旨在删除与该窗口对象关联的小部件。

与任何小部件一样，要删除实际的小部件，您需要调用destroy小部件本身的方法。

我的问题是......当我将 ComboBox 和 Entry 小部件放在 canvas2 上时，它们不会被 canvas2.delete("all") 删除。

那是因为当您使用 时place，您不会创建画布对象。要使delete命令起作用，您必须调用create_window组合框和条目小部件。

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