Tkinter.Entry（）向上/向下键进行跟踪...有没有办法使用ttk.Entry（）？

Question

Using this code fragment, up and down keys (u"uf700", u"uf701") pass through to the trace:

import Tkinter as tk
import ttk

def tracesv(var):
    print var

class foo()
    def __init__(self, parent=None):
        self.win = tk.Toplevel()
        self.svFrame = ttk.Frame(self.win)
        self.svFrame.grid()

        self.sv = tk.StringVar()
        self.sv.trace('w', lambda nm, idx, mode, var=self.sv: tracesv(var))
        self.svEntry = tk.Entry(self.svFrame, textvariable=self.sv)
        self.svEntry.grid()
..... etc.

If I replace tk.Entry() with ttk.Entry(), the up and down keys do not pass through to the trace. Is there a way to make this work with ttk.Entry()?

Answer 1

It sounds like you've found a bug in Tkinter on the mac because arrow keys should not be passed through to the variable trace. The variable trace is designed to be called when the variable is modified. Unless the up and down arrows modify the value then they shouldn't cause the trace to fire.

Since this is a bug, there's no good way to force the bug upon other widgets such as the ttk.Entry widget.

If you're looking for a way to have a function called when the user presses the up or down keys, the proper way is to add bindings to the widget for those keys.