python - TKinter focus 命令不适用于表单堆栈中第二个调用表单的小部件

Question

这个问题已经有答案了:

Tkinter focus_set and focus_force not working as expected (2 个回答)

已关闭 7 年前。

我使用了 Switch between two frames in tkinter 中的代码(如下)(感谢 Brian Oakley )在我使用 Python3.5 + Tkinter 的第一个试点项目中，在“聚焦” Entry 时遇到问题来自第二种形式( PageOne )的小部件，焦点根本不起作用。

但是，如果我从第一个或起始表单( StartPage )中“聚焦”任何小部件，它就会起作用!如果我先切换调用 PageOne之前StartPage现在，第二种形式的“焦点”就可以发挥作用了。您能否提供一些提示，告诉我如何根据下面的代码对第二种表单 ( PageOne ) 上的任何小部件进行“焦点”处理？

import tkinter as tk
TITLE_FONT = ("Helvetica", 18, "bold")

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

       # the container is where we'll stack a bunch of frames
       # on top of each other, then the one we want visible
       # will be raised above the others
       container = tk.Frame(self)
       container.pack(side="top", fill="both", expand=True)
       container.grid_rowconfigure(0, weight=1)
       container.grid_columnconfigure(0, weight=1)

       self.frames = {}
       for F in (StartPage, PageOne, PageTwo):
           page_name = F.__name__
           frame = F(parent=container, controller=self)
           self.frames[page_name] = frame

           # put all of the pages in the same location;
           # the one on the top of the stacking order
           # will be the one that is visible.
           frame.grid(row=0, column=0, sticky="nsew")

       self.show_frame("StartPage")

    def show_frame(self, page_name):
        '''Show a frame for the given page name'''
        frame = self.frames[page_name]
        frame.tkraise()


class StartPage(tk.Frame):

    def __init__(self, parent, controller):
        tk.Frame.__init__(self, parent)
        self.controller = controller
        label = tk.Label(self, text="This is the start page", font=TITLE_FONT)
        label.pack(side="top", fill="x", pady=10)

        button1 = tk.Button(self, text="Go to Page One",
                            command=lambda: controller.show_frame("PageOne"))
        button2 = tk.Button(self, text="Go to Page Two",
                            command=lambda: controller.show_frame("PageTwo"))
        button1.pack()
        button2.pack()


class PageOne(tk.Frame):

    def __init__(self, parent, controller):
        tk.Frame.__init__(self, parent)
        self.controller = controller
        label = tk.Label(self, text="This is page 1", font=TITLE_FONT)
        label.pack(side="top", fill="x", pady=10)
        button = tk.Button(self, text="Go to the start page",
                           command=lambda: controller.show_frame("StartPage"))
        button.pack()


class PageTwo(tk.Frame):

    def __init__(self, parent, controller):
        tk.Frame.__init__(self, parent)
        self.controller = controller
        label = tk.Label(self, text="This is page 2", font=TITLE_FONT)
        label.pack(side="top", fill="x", pady=10)
        button = tk.Button(self, text="Go to the start page",
                           command=lambda: controller.show_frame("StartPage"))
        button.pack()

if __name__ == "__main__":
    app = SampleApp()
    app.mainloop()

Answer 1

我能够找到这个问题的答案，我从这篇文章中找到了它。 anderswb给出了解释

What you are doing in the init method of DIS is to draw all of the pages, basically on top of each other, and then you use tkraise to pull the one you need to the front using tkraise(). For some reason this seems to mess up the focus, so you need to set the focus after you've pulled it to the front. That is why I've added an extra method which will be called on all of you pages after it has been raised. – anderswb Oct 20 '15 at 19:27

tkinter-focus-set-and-focus-force-not-working-as-expected