问题内容
我试图让按钮返回我在“条目”字段中输入的任何值，但它始终返回 xml 文件中设置的默认值。该程序在报告值时似乎忽略了我在框中输入的内容。
这是我的代码：
from tkinter import *
import tkinter as tk
from formation import appbuilder
root = tk.tk()
root.withdraw()
app = appbuilder(path="calculator.xml")
def calculate(event=none):
# event parameter needs to be there because using the bind method passes an event object
# access the expr_var we created earlier to determine the current expression entered
expr = app.expr_var.get()
# evaluate the expression
try:
result = expr
except exception:
# if the expression entered was malformed and could not be evaluated
# we will display an error message instead
result = "invalid expression"
# display the result
app.result.config(text=result)
app.connect_callbacks(globals())
app.mainloop()这将调用包含以下代码的 xml 文件：
我使用 formationstudio 构建 tkinter gui。 我不确定我做错了什么，或者我是否应该采取完全不同的方法。
正确答案
这是因为tk()有两个实例：
- 您明确创建的
- 隐式创建的
appbuilder
删除显式创建的实例。
from formation import AppBuilder
app = AppBuilder(path="calculator.xml")
def calculate(event=None):
# event parameter needs to be there because using the bind method passes an event object
# access the expr_var we created earlier to determine the current expression entered
expr = app.expr_var.get()
# evaluate the expression
try:
result = expr
except Exception:
# if the expression entered was malformed and could not be evaluated
# we will display an error message instead
result = "Invalid expression"
# display the result
app.result.config(text=result)
app.connect_callbacks(globals())
app.mainloop() 
