从单选按钮获取输入

Question

我正在使用Tkinter和graphics.py（Tkinter的一个封装）来创建一个比较简单的积分器（找出图形下的面积），并且有一个图形用户界面（GUI）。目前，积分器的主要“控制面板”与实际的图形是分开的（图形是用graphics.py制作的）。我使用了Tkinter的Radiobutton()来选择积分类型（左矩形法、右矩形法、梯形法或辛普森法）。

我的问题是，我无法获取到单选按钮的输出。我是参考了TutorialsPoint: Tkinter Radiobutton的例子。

这是我的代码：

class FunctionInput:
        def __init__(self, master, window, items):
            self.window = window
            self.items = items
            self.runProgram = True
            self.typeChoice = tk.StringVar()
            self.frame = tk.Frame(master)
            self.typeFrame = tk.Frame(self.frame)
            self.quitButton = tk.Button(self.frame, text = 'Quit', command = self.frame.quit)
            self.optLabel = tk.Label(self.frame, text = 'Type of Approximation: ')
            self.optL = tk.Radiobutton(self.typeFrame, text = 'Left Rectangular', variable = self.typeChoice, value = 'l')
            self.optR = tk.Radiobutton(self.typeFrame, text = 'Right Rectangular', variable = self.typeChoice, value = 'r')
            self.optT = tk.Radiobutton(self.typeFrame, text = 'Trapezoidal', variable = self.typeChoice, value = 't')
            self.optS = tk.Radiobutton(self.typeFrame, text = 'Simpsons Rule', variable = self.typeChoice, value = 's')
            self.optL.grid(row = 1, column = 1, padx = 5, pady = 5)
            self.optR.grid(row = 1, column = 2, padx = 5, pady = 5)
            self.optT.grid(row = 2, column = 1, padx = 5, pady = 5)
            self.optS.grid(row = 2, column = 2, padx = 5, pady = 5)
            self.optLabel.grid(row = 4)
            self.typeFrame.grid(row = 5)
            self.quitButton.grid(row = 6)
            # there were numerous other widgets and frames, but I only included the relevant ones
            self.frame.grid()

        def getInput(self):
            type_integration = self.typeChoice.get()
            self.frame.quit()
            return type_integration


def main():
    # some other code, win and axisLabels are defined prior to this
    root = tk.Tk(className = ' Function Grapher')
    app = FunctionInput(root, win, axisLabels)
    root.rowconfigure(0, weight = 1)
    root.columnconfigure(0, weight = 1)
    root.mainloop() # there is a button to exit the mainloop in my GUI
    typeIntegration = app.getInput()
    print typeIntegration # trying to debug it

if __name__ == '__main__': main()

但是，它没有打印出变量的值，而是打印了一个空字符串，所以执行上没有问题。root.mainloop()并没有陷入无限循环，因为我在我的GUI中有一个按钮（这里没有显示，因为不相关）可以退出程序。没有出现错误，所以我猜问题出在将选项设置给变量上。非常感谢任何帮助。

另外，顺便提一下，每次我运行程序时，‘右矩形法’、‘梯形法’和‘辛普森法’的单选按钮都是灰色的，像这样：

如果我点击其中一个单选按钮，这种灰色就会消失，但在那之前，它一直是灰色的。如果有办法解决这个问题，请告诉我。

谢谢！

Answer 1

我没有看到退出按钮的部分，但你的代码大致是这样的：

1. 启动主循环
2. 退出按钮的事件处理器会调用 root.quit()
3. 在 getInput 中，获取值并调用 self.frame.quit()

在主循环之后调用Tkinter的函数可能会导致一些问题，所以你应该先获取StringVar的值，然后再退出图形界面的循环。这是一个基于你代码的有效示例：

import Tkinter as tk

class App():
    def __init__(self, master):
        self.master = master
        self.type_integration = None
        self.typeChoice = tk.StringVar()
        self.typeChoice.set(None) # This fixes the grayness of the radio buttons!
        self.typeFrame = tk.Frame(master)
        OPTIONS = [('Left Rectangular', 'l'),
                   ('Right Rectangular', 'r'),
                   ('Trapezoidal', 't'),
                   ('Simpsons Rule', 's')]
        for text, value in OPTIONS:
            tk.Radiobutton(self.typeFrame, text=text, variable=self.typeChoice, value=value).pack()
        tk.Button(self.typeFrame, text="Exit", command=self.exit).pack()
        self.typeFrame.pack()
    def exit(self):
        self.type_integration = self.typeChoice.get()
        self.master.destroy() # self.master.quit() freezes the GUI
    def getinput(self):
        return self.type_integration

master = tk.Tk()
app = App(master)
tk.mainloop()
print app.getinput()

Answer 2

问题在于，因为我使用了多个其他的小部件，所以我需要把 StringVar() 的 master 参数设置为 self.typeFrame：

class FunctionInput:
        def __init__(self, master, window, items):
            self.window = window
            self.items = items
            self.runProgram = True
            self.frame = tk.Frame(master)
            self.typeFrame = tk.Frame(self.frame)
            self.typeChoice = tk.StringVar(self.typeFrame)
            self.quitButton = tk.Button(self.frame, text = 'Quit', command = self.frame.quit)
            self.optLabel = tk.Label(self.frame, text = 'Type of Approximation: ')
            self.optL = tk.Radiobutton(self.typeFrame, text = 'Left Rectangular', variable = self.typeChoice, value = 'l')
            self.optR = tk.Radiobutton(self.typeFrame, text = 'Right Rectangular', variable = self.typeChoice, value = 'r')
            self.optT = tk.Radiobutton(self.typeFrame, text = 'Trapezoidal', variable = self.typeChoice, value = 't')
            self.optS = tk.Radiobutton(self.typeFrame, text = 'Simpsons Rule', variable = self.typeChoice, value = 's')
            self.optL.grid(row = 1, column = 1, padx = 5, pady = 5)
            self.optR.grid(row = 1, column = 2, padx = 5, pady = 5)
            self.optT.grid(row = 2, column = 1, padx = 5, pady = 5)
            self.optS.grid(row = 2, column = 2, padx = 5, pady = 5)
            self.optLabel.grid(row = 4)
            self.typeFrame.grid(row = 5)
            self.quitButton.grid(row = 6)
            # there were numerous other widgets and frames, but I only included the relevant ones
            self.frame.grid()

        def getInput(self):
            type_integration = self.typeChoice.get()
            self.frame.quit()
            return type_integration


def main():
    # some other code, win and axisLabels are defined prior to this
    root = tk.Tk(className = ' Function Grapher')
    app = FunctionInput(root, win, axisLabels)
    root.rowconfigure(0, weight = 1)
    root.columnconfigure(0, weight = 1)
    root.mainloop() # there is a button to exit the mainloop in my GUI
    print app.getInput()

if __name__ == '__main__': main()

另外，正如 @A. Rodas 所说，为了去掉灰色的部分，我做了：

self.typeFrame = tk.Frame(self.frame)
self.typeChoice = tk.StringVar(self.typeFrame)
self.typeChoice.set(None)