如何编写函数，通过相关变量将点击按钮的编号添加到PIN编号条目中？

Question

我正在尝试使用python和tkinter构建虚拟numpad（1、2和3）。你知道吗

如果我按1（按钮1），则帐户\号\项应更改为1，如果我按2，则帐户\号\项应相应更改。你知道吗

我试过这个密码，但是。你知道吗

    import tkinter as tk
    win = tk.Tk()

    def handle_pin_button(event):
        '''Function to add the number of the button clicked to the PIN number entry via its associated variable.'''
        # Limit to 4 chars in length
        # Set the new pin number on the pin_number_var


    def create_login_screen():
        accLabel = tk.Label(win, text="Acount Number / Pin")
        accLabel.grid(row=1, column=0)

        account_number_var = tk.StringVar()
        account_number_entry = tk.Entry(win, textvariable=account_number_var)
        account_number_entry.grid(row=1, column=1)
        account_number_entry.focus_set()

        pin_number_var = tk.StringVar()
        account_pin_entry = tk.Entry(win, show='*', text='PIN Number', textvariable=pin_number_var)
        account_pin_entry.grid(row=1, column=2)

        # Buttons 1, 2 and 3 here. Buttons are bound to 'handle_pin_button' function via '<Button-1>' event.
        button1 = tk.Button(text="1")
        button1.bind('<Button-1>', handle_pin_button)
        button1.grid(row=2, column=0, sticky="NESW")
        button2 = tk.Button(text="2")
        button2.bind('<Button-1>', handle_pin_button)
        button2.grid(row=2, column=1, sticky="NESW")
        button3 = tk.Button(text="3")
        button3.bind('<Button-1>', handle_pin_button)
        button3.grid(row=2, column=2, sticky="NESW")


    create_login_screen()
    tk.mainloop()

Answer 1

您需要在函数create_login_screen()之外创建帐号，否则当函数退出时它将被垃圾收集。你知道吗

将按钮绑定到函数的常用方法是使用参数command。当您有一个函数处理来自多个按钮的回调时，通常的方法是使用lambda。你知道吗

示例如下：

import tkinter as tk
win = tk.Tk()

account_number_var = tk.StringVar() # Create outside function
pin_number_var = tk.StringVar()

def handle_pin_button(digit):
    account_number_var.set(digit)

def create_login_screen():
    accLabel = tk.Label(win, text="Acount Number / Pin")
    accLabel.grid(row=1, column=0)

    account_number_entry = tk.Entry(win, textvariable=account_number_var)
    account_number_entry.grid(row=1, column=1)
    account_number_entry.focus_set()

    account_pin_entry = tk.Entry(win, show='*', text='PIN Number',
                                 textvariable=pin_number_var)
    account_pin_entry.grid(row=1, column=2)

    # Buttons 1, 2 and 3 here. Buttons are bound to 'handle_pin_button' function via '<Button-1>' event.
    button1 = tk.Button(text="1", command=lambda:handle_pin_button("1"))
    button1.grid(row=2, column=0, sticky="NESW")
    button2 = tk.Button(text="2", command=lambda:handle_pin_button("2"))
    button2.grid(row=2, column=1, sticky="NESW")
    button3 = tk.Button(text="3", command=lambda:handle_pin_button("3"))
    button3.grid(row=2, column=2, sticky="NESW")


create_login_screen()
win.mainloop()

如何使用bind()而不是按钮command执行此操作：

首先你需要跟踪按钮。因为它们是在函数中创建的，所以必须在全局范围中保存引用。你知道吗

其次，必须从列表索引计算按钮值，并相应地设置account_number_var。你知道吗

然后将按钮绑定到回调处理程序。你知道吗

import tkinter as tk
win = tk.Tk()

account_number_var = tk.StringVar() # Create outside function
pin_number_var = tk.StringVar()
button_list = []    # Global button reference list

def handle_pin_button(event):
    button_number = button_list.index(event.widget) + 1
    account_number_var.set(str(button_number))

def create_login_screen():
    accLabel = tk.Label(win, text="Acount Number / Pin")
    accLabel.grid(row=1, column=0)

    account_number_entry = tk.Entry(win, textvariable=account_number_var)
    account_number_entry.grid(row=1, column=1)
    account_number_entry.focus_set()

    account_pin_entry = tk.Entry(win, show='*', text='PIN Number',
                                 textvariable=pin_number_var)
    account_pin_entry.grid(row=1, column=2)

    # Buttons 1, 2 and 3 here. Buttons are bound to 'handle_pin_button' function via '<Button-1>' event.
    button1 = tk.Button(text="1")
    button1.grid(row=2, column=0, sticky="NESW")
    button1.bind('<Button-1>', handle_pin_button)
    button_list.append(button1) # Add button to global list
    button2 = tk.Button(text="2")
    button2.grid(row=2, column=1, sticky="NESW")
    button2.bind('<Button-1>', handle_pin_button)
    button_list.append(button2) # Add button to global list
    button3 = tk.Button(text="3")
    button3.grid(row=2, column=2, sticky="NESW")
    button3.bind('<Button-1>', handle_pin_button)
    button_list.append(button3) # Add button to global list


create_login_screen()
win.mainloop()