gistfile1.py

# -*- coding: utf-8 -*-
from javax.swing import JFrame, JLabel, JTextField, JButton, JOptionPane
from java.awt import FlowLayout
from java.awt.event import ActionListener, MouseAdapter

import math

TO_CEL = u"→"
TO_FAHR = u"←"


class TempConverter(JFrame):

    def __init__(self):
        super(TempConverter, self).__init__()
        self._fahr = JTextField(3)
        self._cel = JTextField(3)
        self._cel.setEditable(False)
        self._switcher = JButton(TO_CEL)
        self._switcher.addActionListener(ButtonHandler(self))
        self._fahr.addActionListener(
            Handler(self._cel,
                    lambda x: int(math.floor((x - 32) * 5/9.0))))

        self._cel.addActionListener(
            Handler(self._fahr,
                    lambda x: int(math.floor((9/5.0 * x) + 32))))

        content = self.getContentPane()
        content.setLayout(FlowLayout())

        for n in [JLabel(u"Fahrenheit:"), self._fahr, self._switcher,
                  JLabel(u"Celsius:"), self._cel]:
            content.add(n)

        self.setSize(350, 60)
        self.setResizable(False)
        self.setVisible(True)


class ButtonHandler(ActionListener):

    def __init__(self, conv):
        self._converter = conv
    
    def actionPerformed(self, event):
        if self._converter._switcher.getText() == TO_CEL:
            self._converter._switcher.setText(TO_FAHR)
            self._converter._fahr.setEditable(False)
            self._converter._cel.setEditable(True)
        else:
            self._converter._switcher.setText(TO_CEL)
            self._converter._fahr.setEditable(True)
            self._converter._cel.setEditable(False)

        self._converter._fahr.setText(u"")
        self._converter._cel.setText(u"")


class Handler(ActionListener):

    def __init__(self, target, converter):
        self._target = target
        self._converter = converter

    def actionPerformed(self, event):
        value = event.getActionCommand()
        if value.isdigit():
            self._target.setText(str(self._converter(int(value))))
        else:
            JOptionPane.showMessageDialog(self._target,
                u"Invalid temperature. Please only use integers.", u"Error",
                JOptionPane.ERROR_MESSAGE)
            self._target.setText(u"")
            

if __name__ == '__main__':
    b = TempConverter()
    b.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE)