用户输入相同的占位符文本 python tkinter

Question

我为 tkinter 制作了一个占位符，并想继续推进它，但是如果用户输入与占位符相同的文本，占位符应该发生的所有效果都会在文本上实现。无论如何要克服这个？

占位符：

import tkinter as tk
from tkinter import ttk

class PlaceholderEntry(tk.Entry):
    '''
    Custom modern Placeholder Entry box, takes positional argument master and placeholder\n
    Use ret() for getting output from entry widget\n
    Use ins() for inserting into entry widget\n
    Use remove() for deleting from entry widget\n
    ISSUES: What if the user types exactly same text as the placeholders in the entrybox?
    '''

    def __init__(self, master, placeholder, **kwargs):
        # style for ttk widget
        self.s = ttk.Style()
        self.s.configure('my.TEntry')

        # init entry box
        ttk.Entry.__init__(self, master, style='my.TEntry', **kwargs)
        self.text = placeholder

        # add placeholder if box empty
        self.add()

        # bindings of the widget
        self.bind('<FocusIn>', self.clear)
        self.bind('<FocusOut>', self.add)
        self.bind_all('<Key>', self.normal)
        self.bind_all('<Button-1>', self.cursor)

    def clear(self, *args):
        if self.get() == self.text:  # remove placeholder when focus gain
            self.delete(0, tk.END)
            self.s.configure('my.TEntry', foreground='black',
                             font=(0, 0, 'normal'))

    def add(self, *args):
        if self.get() == '':  # if no text add placeholder
            self.s.configure('my.TEntry', foreground='grey',
                             font=(0, 0, 'bold'))
            self.insert(0, self.text)  # insert placeholder
            self.icursor(0)  # move insertion cursor to start of entrybox

    def normal(self, *args):
        self.s.configure('my.TEntry', foreground='black',
                         font=(0, 0, 'normal'))  # set normal font
        self.add()  # if empty add placeholder
        if self.get() == self.text:  # clear the placeholder if starts typing
            self.bind('<Key>', self.clear)
            self.icursor(-1)  # keep insertion cursor to the end

    def ret(self):  # custom method to get the text
        if self.get() == self.text:
            return None
        else:
            return self.get()

    def ins(self, index, string):  # custom method to insert into entry
        self.clear()
        self.insert(index, string)

    def remove(self, first, last):  # custom method to remove from entry
        if self.get() != self.text:
            self.delete(first, last)
            self.add()

    def cursor(self, *args):  # method to not allow user to move cursor when placeholder there
        if self.get() == self.text:
            self.icursor(0)

if __name__ == '__main__':
    root = tk.Tk()
    plc = PlaceholderEntry(root,placeholder='Type')
    plc.pack(padx=10,pady=10)
    root.mainloop()

您可以通过在框中键入类型来重现该问题，它会删除进一步的插入，因为它会将条目误认为是占位符。

提前致谢:D

Answer 1

有点老套的解决方案，但为什么不在占位符文本的开头添加 space（或 non-printable 字符）

plc = PlaceholderEntry(root,placeholder=' Type')

或

self.text = "\x00" + placeholder

这将确保用户输入的文本不会与占位符文本匹配

Answer 2

因为您有一个自定义 class，所以在添加占位符文本时很容易设置标志，在删除占位符时也很容易取消设置。那就只需要在获取值时检查是否设置了标志即可。

def add(self, *args):
    if self.get() == '':  # if no text add placeholder
        ...
        self._has_placeholder = True

def clear(self, *args):
    if self.get() == self.text:  # remove placeholder when focus gain
        self._has_placeholder = False
        ...

用户输入相同的占位符文本 python tkinter

User entering same placeholder text python tkinter

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placeholder