tkinter 输入字段自动更新

Question

每单击一次鼠标左键，self.LEFT_MB_Counter 就会增加，因此值始终在变化。我希望self.LEFT_MB_Counter 中的值显示在输入字段self.left_MB_entry 中，但我无法实现。

如何让输入字段始终更新并显示self.LEFT_MB_Counter 中的当前值？

from win32api import GetKeyState
import tkinter.ttk
import tkinter


class MainApplication:
    """Class that creates the widgets and window."""
    def __init__(self, master):
        """Method that creates the class constructor."""
        self.master = master
        self.var = tkinter.IntVar(value=0)   
        self.left_MB_entry = self.Entry(self.var)
        self.left_MB_entry.grid()

    def Entry(self, text_var, justify="center"):
        """Method that defines a default entry field."""
        entry = tkinter.ttk.Entry(self.master, textvariable=text_var, justify=justify)
        return entry

class MouseCounter:
    """Class that counts mouse button clicks."""
    def __init__(self):
        """Method that creates the class constructor."""
        self.LEFT_MB = 0x01  # Virtual-key code from Microsoft for LEFT MButton
        self.Old_State_LEFT_MB = GetKeyState(self.LEFT_MB)  # LEFT MButton Down = -127 or -128, MButton Up = 0 or 1
        self.LEFT_MB_Counter = 0  # Initialize to 0

    def count(self):
        # Following block of code monitors LEFT MButton
        New_State_LEFT_MB = GetKeyState(self.LEFT_MB)
        if New_State_LEFT_MB != self.Old_State_LEFT_MB:  # Button state changed
            self.Old_State_LEFT_MB = New_State_LEFT_MB
            print(New_State_LEFT_MB)
            if New_State_LEFT_MB < 0:
                self.LEFT_MB_Counter += 1
                print("Count:", self.LEFT_MB_Counter)
                print('Left Button Pressed')
            else:
                print('Left Button Released')
        root.after(1, self.count)


root = tkinter.Tk()
root.style = tkinter.ttk.Style()
#  ('winnative', 'clam', 'alt', 'default', 'classic', 'vista', 'xpnative')
root.style.theme_use("clam")
APP = MainApplication(root)  # Create object instance of the user interface
root.after(0, MouseCounter().count())
root.mainloop()  # Display the user interface

Answer 1

解决方案概述

问题的根源在于MouseCounter 的实例没有引用应用程序，因此不会影响应用程序中的任何内容。这不是 tkinter 独有的，它只是一个基本的 python 原则。要更改对象，您需要对对象的引用。

一旦您确定MouseCounter 的实例引用了MainApplication 的实例，问题就变得相当容易解决了。

解决方案详情

您需要做的第一件事是将var 与条目小部件正确关联。您的代码将其作为位置参数传递，这不是正确的方法。您需要将变量分配给textvariable 属性：

    self.var = tkinter.IntVar(value=0)   
    self.left_MB_entry = self.Entry(textvariable=self.var)

接下来，您需要确保 MouseCounter 能够被传递给主应用程序的一个实例：

class MouseCounter:
    """Class that counts mouse button clicks."""
    def __init__(self, master):
        self.master = master
        ...

创建实例时，传入APP作为MainApplication的实例：

APP = MainApplication(root)
mc = MouseCounter(APP) 
root.after(0, mc.count)

接下来，您只需从您的柜台更新var：

def count(self):
    ...
        if New_State_LEFT_MB < 0:
            ...
            self.master.var.set(self.LEFT_MB_Counter)
            ...

---

注意：您对after 的工作原理有一点误解。它不影响代码，但如果你要使用它，你应该正确使用它。

考虑这段代码：

root.after(0, MouseCounter().count())

它在功能上与以下内容相同：

result = MouseCounter().count()
root.after(0, None)

after 需要一个函数的引用，而不是实际的函数调用。您需要删除尾括号：

root.after(0, MouseCounter().count)

更好的是创建MouseCounter 的实例并保存一个引用，这样它就不会被垃圾收集器收割：

counter = MouseCounter()
root.after(0, counter.count)

Answer 2

您可以通过在MouseCounter.count() 方法中更新MainApplication 实例的名为APP.var 的IntVar 属性来轻松做到这一点。

这是您的代码的修改版本，展示了如何执行此操作：

from win32api import GetKeyState
import tkinter.ttk
import tkinter


class MainApplication:
    """Class that creates the widgets and window."""
    def __init__(self, master):
        """Method that creates the class constructor."""
        self.master = master
        self.var = tkinter.IntVar(value=0)
        self.left_MB_entry = self.Entry(self.var)
        self.left_MB_entry.grid()

    def Entry(self, text_var, justify="center"):
        """Method that defines a default entry field."""
        entry = tkinter.ttk.Entry(self.master, textvariable=text_var, justify=justify)
        return entry

class MouseCounter:
    """Class that counts mouse button clicks."""
    def __init__(self, variable):
        """Method that creates the class constructor."""
        self.LEFT_MB = 0x01  # Virtual-key code from Microsoft for LEFT MButton
        self.Old_State_LEFT_MB = GetKeyState(self.LEFT_MB)  # LEFT MButton Down = -127 or -128, MButton Up = 0 or 1
        self.LEFT_MB_Counter = 0  # Initialize to 0
        self.variable = variable
        self.variable.set(self.LEFT_MB_Counter)

    def count(self):
        # Following block of code monitors LEFT MButton
        New_State_LEFT_MB = GetKeyState(self.LEFT_MB)
        if New_State_LEFT_MB != self.Old_State_LEFT_MB:  # Button state changed
            self.Old_State_LEFT_MB = New_State_LEFT_MB
            print(New_State_LEFT_MB)
            if New_State_LEFT_MB < 0:
                self.LEFT_MB_Counter += 1
                self.variable.set(self.LEFT_MB_Counter)
                print("Count:", self.LEFT_MB_Counter)
                print('Left Button Pressed')
            else:
                print('Left Button Released')
        root.after(1, self.count)


root = tkinter.Tk()
root.style = tkinter.ttk.Style()
#  ('winnative', 'clam', 'alt', 'default', 'classic', 'vista', 'xpnative')
root.style.theme_use("clam")
APP = MainApplication(root)  # Create object instance of the user interface
mouse_counter = MouseCounter(APP.var)  # Create an instance outside of mainloop.
root.after(0, mouse_counter.count)
root.mainloop()  # Display the user interface

Answer 3

一种选择是将LEFT_MB_Counter 设为IntVar，Entry 可以直接使用：

from multiprocessing import Process, Pipe
import time
from win32api import GetKeyState
import tkinter.ttk
import tkinter


class MainApplication(object):
    """Class that creates the widgets and window."""
    def __init__(self, master):
        """Method that creates the class constructor."""
        self.master = master
        self.mc = MouseCounter(master)
        root.after(0, self.mc.count)
        self.left_MB_entry = self.Entry(self.mc.LEFT_MB_Counter)
        self.left_MB_entry.grid()


    def Entry(self, text_var, justify="center"):
        """Method that defines a default entry field."""
        entry = tkinter.ttk.Entry(self.master, textvariable=text_var, justify=justify)
        return entry

class MouseCounter:
    """Class that counts mouse button clicks."""
    def __init__(self, master):
        """Method that creates the class constructor."""
        self.master = master
        self.LEFT_MB = 0x01  # Virtual-key code from Microsoft for LEFT MButton
        self.Old_State_LEFT_MB = GetKeyState(self.LEFT_MB)  # LEFT MButton Down = -127 or -128, MButton Up = 0 or 1
        self.LEFT_MB_Counter = tkinter.IntVar(0)  # Initialize to 0

    def count(self):
        # Following block of code monitors LEFT MButton
        New_State_LEFT_MB = GetKeyState(self.LEFT_MB)
        if New_State_LEFT_MB != self.Old_State_LEFT_MB:  # Button state changed
            self.Old_State_LEFT_MB = New_State_LEFT_MB
            print(New_State_LEFT_MB)
            if New_State_LEFT_MB < 0:
                self.LEFT_MB_Counter.set(self.LEFT_MB_Counter.get() + 1)
                print("Count:", self.LEFT_MB_Counter.get())
                print('Left Button Pressed')
            else:
                print('Left Button Released')
        self.master.after(1, self.count)


root = tkinter.Tk()
root.style = tkinter.ttk.Style()
root.style.theme_use("clam")
APP = MainApplication(root) 

root.mainloop()  # Display the user interface