带有 tkinter 消息框和缩放按钮的无限循环（Python | Tkinter）

Question

我不小心创建了一个无限循环:D
当用户操作 tkinter Scale 时，我想通过下面的函数调用警告（如果文件不存在）。此消息应仅显示一次。但是当用户点击（在中间）tkinter Scale 按钮时，Scale 按钮被拖到最后并一次又一次地调用消息。

我怎样才能避免这种情况？

def change_max_y(v):

    try:
        # Some functions to check if the file exists
        # Open some json file
        # Do some calculation

    except FileNotFoundError:
        # Some function to open the messagebox:
        comment = tk.messagebox.askyesno('Title', "Something is missing.", icon='warning')
        
        if comment:
            # Do something
        else:
            return

ttk.Scale(settingsWin, orient=tk.HORIZONTAL, from_=0, to=4, length=110, command=change_max_y). \
    place(x=210, y=90)

Answer 1

您可以定义一个初始值为 0 的全局变量（我知道这是不好的做法，但有时必须这样做）。在您的回调函数中，您查看该变量是否为 0，如果是，则显示您的消息框并将其设置为 1。如果否，您什么都不做。您提供的代码已相应修改：

already_shown = 0

def change_max_y(v):

    try:
        # Some functions to check if the file exists
        # Open some json file
        # Do some calculation

    except FileNotFoundError:
        # Some function to open the messagebox:
        if not already_shown:
            comment = tk.messagebox.askyesno('Title', "Something is missing.", icon='warning')
            already_shown = 1
        
            if comment:
                # Do something
        else:
            return # note : you can delete this else statement, as the function 
                   # will return None by itself when there is nothing more to be
                   # done

ttk.Scale(settingsWin, orient=tk.HORIZONTAL, from_=0, to=4, length=110, command=change_max_y). \
    place(x=210, y=90)

带有 tkinter 消息框和缩放按钮的无限循环（Python | Tkinter）

Infinite loop with tkinter messagebox and scale button (Python | Tkinter)

python

tkinter

scale

messagebox