Tkinter：如何在元组中显示下一帧

Question

我正在尝试为 tkinter 按钮编写一个方法，该方法将遍历帧元组并在我单击下一个按钮时显示下一帧。目标是编写函数，这样我只需将“self”（对于当前可见的框架对象）作为参数传递。

我已经浏览了一些示例，这些示例允许我通过将新框架作为参数传递给函数来切换到新框架。我目前已经按照这些思路实施了一些措施作为权宜之计，直到我找到解决当前问题的方法。我不确定要包含多少代码，但我已经将它配对，以便它仍然可以正常运行，并且问题最少。

App.next_frame() 中的元组 App.frames 和 else 块是问题区域。

class App(tk.Frame):
    def __init__(self, master = None):
        super().__init__(master)
        self.master = master
        self.pack()

        #### Add any new pages to this tuple ####
        self.frames = (StartPage, Page2)
        self.current_frame = None
        self.next_frame(self.current_frame)

    def next_frame(self, cframe_class):
        '''Set the visible page to the next frame in the frames tuple.
        Pass self to the cframe_class argument'''
        if self.current_frame == None:
            '''If the application has just started, this block will run
            in order to set the current frame to the start page.'''
            self.current_frame = StartPage(self)
            self.current_frame.pack()
        else:         ##### Problem #####
            cfi = self.frames.index(cframe_class)
            #### "ValueError: tuple.index(x): x not in tuple" ####
            cfi += 1
            self.current_frame.destroy()
            self.current_frame = self.frames[cfi]
            self.current_frame.pack()

class StartPage(tk.Frame):
    def __init__(self, master = None):
        super().__init__(master)
        tk.ttk.Button(self, text = "Test Next",
                        command = lambda: master.next_frame(self)).pack()

class Page2(tk.Frame):
    def __init__(self, master = None):
        super().__init__(master)
        tk.ttk.Label(self, text = "This is Page 2").pack()

def main():
    root = tk.Tk()
    app = App(root)
    app.mainloop()    #app.mainloop() or root.mainloop()?

if __name__ == "__main__":
    main()

调试器在 cfi 变量行抛出 "ValueError: tuple.index(x): x not in tuple"。当我在单击下一个按钮后单步执行该函数时，调试器告诉我我的参数“cframe_class”的 id 为：

<__main__.StartPage object .!app.!startpage>

我理解该行的第一部分，但我不确定如何解释 object.!app.!startpage> 部分。看起来应该这样读：“Startpage 是一个继承自 NOTapp、NOTstartpage 的对象”，但我不明白为什么会这样。

我的元组中的 StartPage 对象的 id 为：

<class '__main__.StartPage'>

Answer 1

也许您可以使用存储为属性的索引来跟踪当前帧，而不是传递参数。

import tkinter as tk
from tkinter import ttk

class App(tk.Frame):
    def __init__(self, master = None):
        super().__init__(master)
        self.master = master
        self.pack()
        self.cfi = 0
        #### Add any new pages to this tuple ####
        self.frames = (StartPage(self), Page2(self))
        self.current_frame = None
        self.next_frame()

    def next_frame(self):
        '''Set the visible page to the next frame in the frames tuple.
        Pass self to the cframe_class argument'''
        if self.cfi == 0:
            '''If the application has just started, this block will run
            in order to set the current frame to the start page.'''
            self.current_frame = self.frames[0]
            self.current_frame.pack()
            self.cfi +=1
        else:
            self.current_frame.pack_forget()
            try:
                self.current_frame = self.frames[self.cfi]
            except IndexError:
                self.current_frame = self.frames[0]
                self.cfi = 0
            self.current_frame.pack()
            self.cfi += 1

class StartPage(tk.Frame):
    def __init__(self, master = None):
        super().__init__(master)
        tk.Button(self, text = "Test Next", command = master.next_frame).pack()

class Page2(tk.Frame):
    def __init__(self, master = None):
        super().__init__(master)
        tk.Button(self, text = "This is Page 2",command=master.next_frame).pack()

def main():
    root = tk.Tk()
    app = App(root)
    app.mainloop()    #app.mainloop() or root.mainloop()?

if __name__ == "__main__":
    main()