JTextField limiting character amount input and accepting numeric only

Question

here\'s the code that i have on how to limit the character input length

class JTextFieldLimit extends PlainDocument {
  private int limit;
  // optional uppe         


        

Answer 1

import java.awt.Component;
import java.awt.KeyboardFocusManager;
import java.awt.event.KeyEvent;
import javax.swing.JTextField;
import javax.swing.KeyStroke;
import javax.swing.SwingUtilities;
import javax.swing.text.AbstractDocument;
import javax.swing.text.AttributeSet;
import javax.swing.text.BadLocationException;
import javax.swing.text.Document;
import javax.swing.text.DocumentFilter;
import javax.swing.text.JTextComponent;
import org.apache.commons.lang.StringUtils;

public class NumberTextField extends JTextField {

    protected int maxlength = 0;

    public NumberTextField() {
        this(10);
    }

    public NumberTextField(int length) {
        super();
        this.maxlength = length;
        initializeForNumbers();
    }

    public void setMaxLength(int length) {
        this.maxlength = length;
    }

    protected boolean processKeyBinding(KeyStroke ks, KeyEvent e, int condition, boolean pressed) {
        int keyCode = e.getKeyCode();
        if (keyCode == KeyEvent.VK_ENTER || keyCode == KeyEvent.VK_ESCAPE) {
            return false;
        }
        return super.processKeyBinding(ks, e, condition, pressed);
    }

    private void initializeForNumbers() {
        Document document = getDocument();
        if (document != null) {
            ((AbstractDocument) document).setDocumentFilter(new DocumentHandler());
        }
    }

    private class DocumentHandler extends DocumentFilter {

        public void insertString(DocumentFilter.FilterBypass fb,
                int offset, String string, AttributeSet attr)
                throws BadLocationException {
            if (string == null) {
                return;
            } else {
                replace(fb, offset, 0, string, attr);
            }

        }

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

            replace(fb, offset, length, "", null);
        }

        public void replace(final DocumentFilter.FilterBypass fb,
                int offset, int length, String text, AttributeSet attrs)
                throws BadLocationException {

            Document doc = fb.getDocument();
            int currentLength = doc.getLength();
            String currentContent = doc.getText(0, currentLength);
            String before = currentContent.substring(0, offset);
            String after = currentContent.substring(length + offset, currentLength);
            String newValue = before + (text == null ? "" : text) + after;
            if (newValue.length() > maxlength) {
                return;
            } else {
                checkInput(newValue, offset);
                fb.replace(offset, length, text, attrs);

                if (doc.getLength() >= maxlength) {
                    SwingUtilities.invokeLater(new Runnable() {
                        public void run() {
                            Component c = KeyboardFocusManager.getCurrentKeyboardFocusManager().getFocusOwner();
                            if (c != null && c instanceof JTextComponent) {
                                JTextComponent component = (JTextComponent) c;
                                Document compDoc = component.getDocument();
                                if (compDoc.equals(fb.getDocument())) {
                                    KeyboardFocusManager.getCurrentKeyboardFocusManager().focusNextComponent();
                                }
                            }
                        }
                    });
                    return;
                }
            }
        }

        private void checkInput(String proposedValue, int offset)
                throws BadLocationException {
            if (proposedValue.length() > 0 && !StringUtils.isNumeric(proposedValue)) {
                throw new BadLocationException(
                        proposedValue, offset);
            }
        }
    }
}