Tkinter无法从父类继承函数

Question

我是tkinter和面向对象编程的新手。出于某种原因，当运行以下代码并输入admin / password而不是切换帧时，它会出现以下错误：

 Exception in Tkinter callback Traceback (most recent call last):  
 File "C:\Python34\lib\tkinter\__init__.py", line 1533, in __call__
     return self.func(*args)   File "H:\Networ\multiwindowguiskeleton.py", line 44, in checkpassword
     controller.show_frame(messagescreenpagevar) 
 NameError: name 'controller' is not defined

代码是：

import tkinter as tk

class Guiroot(tk.Tk):
    def __init__(self,*args,**kwargs):

        tk.Tk.__init__(self,*args,**kwargs)
        framecontainer = tk.Frame(self)

        framecontainer.pack(side="top",fill="both",expand=True)

        framecontainer.grid_rowconfigure(0,weight=1)
        framecontainer.grid_columnconfigure(0,weight=1)
        self.title("Vault Messenger")

        self.frames = {}

        passwordpagevar = passwordpage(framecontainer,self)   # this is adding the different pages to a list so they can be called forward later.
        messagescreenpagevar = messagescreen(framecontainer,self)

        self.frames[passwordpagevar] = passwordpagevar
        self.frames[messagescreenpagevar] = messagescreenpagevar

        passwordpagevar.grid(row=0 , column = 0, sticky = "nsew")
        messagescreenpagevar.grid(row=0 , column = 0, sticky = "nsew")        

        self.show_frame(passwordpagevar)

    def show_frame(self, cont):
        frame = self.frames[cont]
        frame.tkraise()

class passwordpage(tk.Frame):
    def checkpassword(self):
        if self.usernamebox.get() == "admin" and self.passwordbox.get() == "password":
            self.errorlabel['text'] = "Correct entry/pass"
            controller.show_frame(messagescreenpagevar)
        else:
            self.errorlabel['text'] = "Incorrect entry/pass"

    def __init__(self, parent, controller):
        tk.Frame.__init__(self,parent)

        self.usernamelabel = tk.Label(self,text="Username:")
        self.usernamebox = tk.Entry(self)
        self.passwordlabel = tk.Label(self, text="Password:")
        self.passwordbox = tk.Entry(self,show="*")
        self.errorlabel = tk.Label(self, text = "")
        self.enterdetails = tk.Button(self, text = "Enter", command = self.checkpassword)


        self.usernamelabel.grid(row=0)
        self.usernamebox.grid(row=1)
        self.passwordlabel.grid(row=2)
        self.passwordbox.grid(row=3)
        self.errorlabel.grid(row=4)
        self.enterdetails.grid(row=5)

class messagescreen(tk.Frame):
    def __init__(self, parent, controller):
        tk.Frame.__init__(self,parent)

        self.userlist = tk.Listbox(self, width = 20, height = 20)
        self.chatbox = tk.Text(self, width = 50,height = 20)
        self.chatentry = tk.Entry(self, width = 60)
        self.sendmessagebutton = tk.Button(self, text = "Send")


        self.userlist.grid(row=0,column=0)
        self.chatbox.grid(row=0,column=1, columnspan = 2)
        self.chatentry.grid(row=1,column=1)
        self.sendmessagebutton.grid(row=1,column= 2)

root = Guiroot()
root.mainloop()

Answer 1

在第44行中，解释器找到以下表达式

controller.show_frame(messagescreenpagevar)

在此范围内，controller未定义。这就是解释器提示错误name 'controller' is not defined的原因。

Python使用词法范围。因此，为了在第44行定义变量controller，您必须在以下位置定义它：

• 方法checkpassword
• 班级passwordpage
• 在您的模块的全局范围内