在JFRAME中制作数字基础转换器

Question

So I have a JFrame file which contains 3 text boxes, a "Convert!" and a "Clear" button. The 3 text boxes are to input numbers from Hexadecimal -- Decimal -- Binary. You can input in any field pertaining to that specific number base and it'll convert that number base into the other 2 number bases.

My question is this : How can I detect which number base I'm supposed to convert from? For example if someone does a conversion, and wants to convert again, and he inputs another value for any number base so that 2 of the values are equivalent in the number bases, and one isn't, the program would mess up as it wouldn't know which one to convert. How can I combat this problem. And if someone is doing their first conversion, how would I be able to detect if there is text in the textbook. Sorry I'm new to jframes and I barely know the syntax.

Answer 1

You could add a DocumentFilter to each JTextField to perform the conversion:

DocumentFilter hexFilter = new DocumentFilter(){

    @Override
    public void replace(FilterBypass fb, int offset, int length, String text, AttributeSet attrs) throws BadLocationException {
        super.replace(fb, offset, length, text, attrs);
        String hexInput = hexTextField.getText();
        //process hex input
    }
};
((AbstractDocument) hexTextField.getDocument()).setDocumentFilter(hexFilter);

The replace method will be invoked everytime the user inserts a text in the text field.

You just have to take the input from the text field and process it.

I'm having this problem because there are 3 text fields and I don't know how I can "detect" in which textbox the user has made an input.

You can add a different DocumentFilter to each text field, so you will always know which text field the user is writing to.

Something like:

((AbstractDocument) hexTextField.getDocument()).setDocumentFilter(hexFilter);
((AbstractDocument) octTextField.getDocument()).setDocumentFilter(octFilter);
((AbstractDocument) binTextField.getDocument()).setDocumentFilter(binFilter);

This way you will always know that binFilter handles binary input, octFilter handles octal input and hexFilter handles hexadecimal input.

---

Another option would be to use a KeyListener , but AFAIK it doesn't react when you paste some text in the text field.

Answer 2

You could place a Listener on each of the text fields and change the other text fields according to which one was changed by the user.

I'm afraid I'm not entirely sure which listener you have to add to receive an event AFTER the text field gets changed (InputMethodListener didn't seem to fire anything and KeyListener fires before the text changes) so in this example I'll use ActionListener, which means the user will have to press "enter" after typing in the number.

final JTextField hex = new JTextField("hex");
final JTextField dec = new JTextField("dec");
ActionListener act = new ActionListener() {
    @Override
    public void actionPerformed(ActionEvent e) {
        if(e.getSource() == hex) {
            dec.setText(Integer.toString(Integer.parseInt(hex.getText(), 16)));
        } else if(e.getSource() == dec) {
            hex.setText(Integer.toHexString(Integer.parseInt(dec.getText())));
        }
    }
};
hex.addActionListener(act);
dec.addActionListener(act);

EDIT: This means you won't need the "Convert!" button though, if you really want that then you'll need to keep track of which text field was edited the last time. Which you could do by doing:

JTextField lastEdited;
private void init() {
    //other init stuff
    final JTextField hex = new JTextField("hex");
    final JTextField dec = new JTextField("dec");
    KeyListener keyListener = new KeyAdapter() {
        @Override
        public void keyTyped(KeyEvent e) {
            lastEdited = (JTextField) e.getSource();
        }
    };
    hex.addKeyListener(keyListener);
    dec.addKeyListener(keyListener);
    JButton convert = new JButton("Convert!");
    convert.addActionListener(new ActionListener() {
        @Override
        public void actionPerformed(ActionEvent e) {
            if(lastEdited == hex) {
                dec.setText(Integer.toString(Integer.parseInt(hex.getText(), 16)));
            } else if(lastEdited == dec) {
                hex.setText(Integer.toHexString(Integer.parseInt(dec.getText())));
            }
        }
    });
    //other init stuff
}