Input text only accepts numbers

Question

I desinged a little swing GUI that has some JTextFields, but it has a validateVariables method that has to validate all the fields that are inside the interface, there's one JTextField called (IP) must accept only int Variables how can i set it up like that?

P.S the JTextfield was created it in netbeans with the palete tool.

Answer 1

This is the javadoc of JTextField http://docs.oracle.com/javase/7/docs/api/javax/swing/JTextField.html

There is an example

public class UpperCaseField extends JTextField {

  public UpperCaseField(int cols) {
    super(cols);
  }

  protected Document createDefaultModel() {
    return new UpperCaseDocument();
  }

  static class UpperCaseDocument extends PlainDocument {

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

        if (str == null) {
          return;
        }
        char[] upper = str.toCharArray();
        for (int i = 0; i < upper.length; i++) {
          upper[i] = Character.toUpperCase(upper[i]);
        }
        super.insertString(offs, new String(upper), a);
      }
    }
  }

This example changes all user input to upper case. Just modify the insertString method, remove all non-digit characters, you can make your text field accept digits only.

Example:

public void insertString(int offs, String str, AttributeSet a)
    throws BadLocationException {
  if (str == null) {
    return;
  }
  super.insertString(offs, str.replaceAll("[^0-9]", ""), a);
}

---- EDIT ----

As @MadProgrammer said, DocumentFilter is another way to do so, for example:

Document document = someJTextField.getDocument();
if (document instanceof AbstractDocument) {
  ((AbstractDocument) doc).setDocumentFilter(new DocumentFilter() {
    public void insertString(DocumentFilter.FilterBypass fb, int offset,  
        String str, AttributeSet a) throws BadLocationException {  
      fb.insertString(offset, str.replaceAll("[^0-9]", ""), a);  
    }
  });
}