JFormattedTextField to format percent numbers?

Question

I would like to format a float number as a percent-value with JFormattedTextField that allows inputs from 0 to 100 percent (converted to 0.0f-1.0f), always shows the percent

Answer 1

1) consider using JSpinner instead of JFormattedTextField because there you can set SpinnerNumberModel for initial values

from API

Integer value = new Integer(50); 
Integer min = new Integer(0);
Integer max = new Integer(100); 
Integer step = new Integer(1);

and with simple hack for JSpinner (with SpinnerNumberModel) it doesn't allows another input as Digits, otherwise is there possible input any of Chars

2) for JFormattedTextField you have to implements

• DocumentListener
• Document

and of both cases for JFormattedTextField you have to write workaround for catch if value is less or more than required range ...

EDIT:

.

.

not true at all, :-) you are so far from ... simple wrong :-), there is small mistake with your result, please look at this code

import java.awt.BorderLayout;
import java.text.NumberFormat;
import javax.swing.*;
import javax.swing.text.*;

public class TestDigitsOnlySpinner {

    public static void main(String... args) {
        SwingUtilities.invokeLater(new Runnable() {

            public void run() {
                JFrame frame = new JFrame("enter digit");
                JSpinner jspinner = makeDigitsOnlySpinnerUsingDocumentFilter();
                frame.getContentPane().add(jspinner, BorderLayout.CENTER);
                frame.getContentPane().add(new JButton("just another widget"), BorderLayout.SOUTH);
                frame.pack();
                frame.setVisible(true);
            }

            private JSpinner makeDigitsOnlySpinnerUsingDocumentFilter() {
                JSpinner spinner = new JSpinner(new SpinnerNumberModel());
                JSpinner.NumberEditor jsEditor = (JSpinner.NumberEditor) spinner.getEditor();
                JFormattedTextField textField = jsEditor.getTextField();
                final DocumentFilter digitOnlyFilter = new DocumentFilter() {

                    @Override
                    public void insertString(FilterBypass fb, int offset, String string, AttributeSet attr) throws BadLocationException {
                        if (stringContainsOnlyDigits(string)) {
                            super.insertString(fb, offset, string, attr);
                        }
                    }

                    @Override
                    public void remove(FilterBypass fb, int offset, int length) throws BadLocationException {
                        super.remove(fb, offset, length);
                    }

                    @Override
                    public void replace(FilterBypass fb, int offset, int length, String text, AttributeSet attrs) throws BadLocationException {
                        if (stringContainsOnlyDigits(text)) {
                            super.replace(fb, offset, length, text, attrs);
                        }
                    }

                    private boolean stringContainsOnlyDigits(String text) {
                        for (int i = 0; i < text.length(); i++) {
                            if (!Character.isDigit(text.charAt(i))) {
                                return false;
                            }
                        }
                        return true;
                    }
                };
                /*NumberFormat format = NumberFormat.getIntegerInstance();
                format.setGroupingUsed(false);// or add the group chars to the filter
                NumberFormat format = NumberFormat.getInstance();*/

                NumberFormat format = NumberFormat.getPercentInstance();
                format.setGroupingUsed(false);
                format.setGroupingUsed(true);// or add the group chars to the filter
                format.setMaximumIntegerDigits(10);
                format.setMaximumFractionDigits(2);
                format.setMinimumFractionDigits(5);
                textField.setFormatterFactory(new DefaultFormatterFactory(new InternationalFormatter(format) {

                    private static final long serialVersionUID = 1L;

                    @Override
                    protected DocumentFilter getDocumentFilter() {
                        return digitOnlyFilter;
                    }
                }));
                return spinner;
            }
        });
    }
}