tkinter：为什么 Combobox 和 Entry widgets 没有被 delete( "all" ) 删除？

Question

我指的是整个小部件，而不是里面的文本。我还试图在论坛上找到一个现有的解决方案。我已经剥离了代码，只显示问题。

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

如果选择"加权图"，然后选择"无向图"，就会出现问题。菜单上的。在"加权图"之后，ComboBox和Entry小部件仍然是(其他所有内容都按预期删除)。我输入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)

Answer 1

为什么不通过delete(" all ")删除组合框和条目小部件?

这就是tkinter的工作原理。canvas delete方法只删除canvas对象。也就是说，在画布上创建的对象使用&;create&;函数(create_rectangle, create_window等)。对于窗口对象，delete方法将删除用create_window创建的画布对象，但它不是用来删除与该窗口对象关联的小部件的。

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

那是因为当你使用place时，你没有创建画布对象。为了使delete命令工作，您必须为combox和条目小部件调用create_window。

Answer 2

在tkinter中销毁一个小部件试试。destroy()

f1=tk.Frame()
f1.destroy()