InputVerifier and, using JComponent's
* setInputVerifier method,
* attach an instance of their subclass to the JComponent whose input they
* want to validate. Before focus is transfered to another Swing component
* that requests it, the input verifier's shouldYieldFocus method is
* called. Focus is transfered only if that method returns true.
* * The following example has two text fields, with the first one expecting * the string "pass" to be entered by the user. If that string is entered in * the first text field, then the user can advance to the second text field * either by clicking in it or by pressing TAB. However, if another string * is entered in the first text field, then the user will be unable to * transfer focus to the second text field. * *
* import java.awt.*;
* import java.util.*;
* import java.awt.event.*;
* import javax.swing.*;
*
* // This program demonstrates the use of the Swing InputVerifier class.
* // It creates two text fields; the first of the text fields expects the
* // string "pass" as input, and will allow focus to advance out of it
* // only after that string is typed in by the user.
*
* public class VerifierTest extends JFrame {
* public VerifierTest() {
* JTextField tf1 = new JTextField ("Type \"pass\" here");
* getContentPane().add (tf1, BorderLayout.NORTH);
* tf1.setInputVerifier(new PassVerifier());
*
* JTextField tf2 = new JTextField ("TextField2");
* getContentPane().add (tf2, BorderLayout.SOUTH);
*
* WindowListener l = new WindowAdapter() {
* public void windowClosing(WindowEvent e) {
* System.exit(0);
* }
* };
* addWindowListener(l);
* }
*
* class PassVerifier extends InputVerifier {
* public boolean verify(JComponent input) {
* JTextField tf = (JTextField) input;
* return "pass".equals(tf.getText());
* }
* }
*
* public static void main(String[] args) {
* Frame f = new VerifierTest();
* f.pack();
* f.setVisible(true);
* }
* }
*
*
* @since 1.3
*/
public abstract class InputVerifier {
/**
* Checks whether the JComponent's input is valid. This method should
* have no side effects. It returns a boolean indicating the status
* of the argument's input.
*
* @param input the JComponent to verify
* @return true when valid, false when invalid
* @see JComponent#setInputVerifier
* @see JComponent#getInputVerifier
*
*/
public abstract boolean verify(JComponent input);
/**
* Calls verify(input) to ensure that the input is valid.
* This method can have side effects. In particular, this method
* is called when the user attempts to advance focus out of the
* argument component into another Swing component in this window.
* If this method returns true, then the focus is transfered
* normally; if it returns false, then the focus remains in
* the argument component.
*
* @param input the JComponent to verify
* @return true when valid, false when invalid
* @see JComponent#setInputVerifier
* @see JComponent#getInputVerifier
*
*/
public boolean shouldYieldFocus(JComponent input) {
return verify(input);
}
}