清除小部件后将文本插入 Tkinter 条目

Question

我想在我的应用程序中添加一个 Entry 小部件，这样当我使用退格按钮清除它时，它会自动插入另一个文本，例如占位符...

我已经创建了以下函数来创建前面所述的占位符，但我还想在用户清除 Entry 小部件后立即添加该占位符文本。这可能吗？

def placeholder(entry, case: str):
    placeholder = f'type the {case} number...'

    def focusIn():
        if entry.get() == placeholder:
            entry.delete(0, tk.END)
            entry.config({'foreground': 'Black'})
    def focusOut():
        if entry.get() == '':
            entry.insert(0, placeholder)
            if entry.get() == placeholder:
                entry.config({'foreground': 'Grey'})

    if entry.get() == '':
        entry.insert(0, placeholder)
        if entry.get() == placeholder:
            entry.config({'foreground': 'Grey'})

    entry.bind('<FocusIn>', lambda event: focusIn())
    entry.bind('<FocusOut>', lambda event: focusOut())

Answer 1

我认为为此您最好使用验证函数而不是绑定事件。这是一个粗略的大纲：

import tkinter as tk

def placeholder(data, event, widget):
    if event == 'key' and data == '':
        print(f'{widget}: user has cleared all data')
    if event == 'key' and data != '':
        print(f'{widget}: user has typed something')
    if event == 'focusout':
        print(f'{widget}: user has left')
    if event == 'focusin':
        print(f'{widget}: user has joined')
    return True # critical!!

root = tk.Tk()
vcmd = root.register(placeholder), '%P', '%V', '%W'
for i in range(1,5):
    ent = tk.Entry(root, validate="all", validatecommand=vcmd)
    ent.pack()
root.mainloop()