Is there a way to put a colon in a jtextfield so it cant be removed?

问题

I want a user to input time, so like 12:00, but I need to figure out a few things and I am wicked lost.

1. Can I limit the text to 5 characters and how?
2. Can I have a colon embedded in the code so that it cant be deleted by the user?
3. Finally, can I take that code and verify that it is only the digits (ignoring the colon of course)

回答1:

The answer is to use a JFormattedTextField and a MaskFormatter.

For example:

String mask = "##:##";
MaskFormatter timeFormatter = new MaskFormatter(mask);
JFormattedTextField formattedField = new JFormattedTextField(timeFormatter);

The Java compiler will require that you catch or throw a ParseException when creating your MaskFormatter, and so be sure to do this.

回答2:

Or just ditch your textfield and opt for two JSpinner instances separated by a JLabel containing the colon (or two JTextField instances).

Not completely sure that this solution will be more intuitive to the user, but I think so.

回答3:

a late answer to an old question; making use of DocumentFilter may achieve that three req's.

a non-production quality code may be like this

String TIME_PATTERN = "^\\d\\d:\\d\\d\\s[AP]M$";

final JTextField tf = new JTextField("00:00 AM", 8);

((AbstractDocument)tf.getDocument()).setDocumentFilter(new DocumentFilter() {
    public void replace(FilterBypass fb, int offs, int length, String str, AttributeSet a) throws BadLocationException {

        String text = fb.getDocument().getText(0, fb.getDocument().getLength());

        text = text.substring(0, offs) + str + text.substring(offs + length);

        if(text.matches(TIME_PATTERN)) {
            super.replace(fb, offs, length, str, a);
            return;
        }

        text = fb.getDocument().getText(0, fb.getDocument().getLength());

        if(offs == 2 || offs == 5)
            tf.setCaretPosition(++offs);

        if(length == 0 && (offs == 0 ||offs == 1 ||offs == 3 ||offs == 4 ||offs == 6))
            length = 1;

        text = text.substring(0, offs) + str + text.substring(offs + length);

        if(!text.matches(TIME_PATTERN))
            return;

        super.replace(fb, offs, length, str, a);

    }

    public void insertString(FilterBypass fb, int offs, String str, AttributeSet a) throws BadLocationException { }

    public void remove(FilterBypass fb, int offset, int length) throws BadLocationException { }

});

来源：https://stackoverflow.com/questions/11215449/is-there-a-way-to-put-a-colon-in-a-jtextfield-so-it-cant-be-removed