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Java > Open Source Codes > javax > swing > InputVerifier


1 /*
2  * @(#)InputVerifier.java 1.9 03/12/19
3  *
4  * Copyright 2004 Sun Microsystems, Inc. All rights reserved.
5  * SUN PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
6  */
7
8 package javax.swing;
9
10 import java.util.*;
11
12 /**
13  * The purpose of this class is to help clients support smooth focus
14  * navigation through GUIs with text fields. Such GUIs often need
15  * to ensure that the text entered by the user is valid (for example,
16  * that it's in
17  * the proper format) before allowing the user to navigate out of
18  * the text field. To do this, clients create a subclass of
19  * <code>InputVerifier</code> and, using <code>JComponent</code>'s
20  * <code>setInputVerifier</code> method,
21  * attach an instance of their subclass to the <code>JComponent</code> whose input they
22  * want to validate. Before focus is transfered to another Swing component
23  * that requests it, the input verifier's <code>shouldYieldFocus</code> method is
24  * called. Focus is transfered only if that method returns <code>true</code>.
25  * <p>
26  * The following example has two text fields, with the first one expecting
27  * the string "pass" to be entered by the user. If that string is entered in
28  * the first text field, then the user can advance to the second text field
29  * either by clicking in it or by pressing TAB. However, if another string
30  * is entered in the first text field, then the user will be unable to
31  * transfer focus to the second text field.
32  * <p>
33  * <pre>
34  * import java.awt.*;
35  * import java.util.*;
36  * import java.awt.event.*;
37  * import javax.swing.*;
38  *
39  * // This program demonstrates the use of the Swing InputVerifier class.
40  * // It creates two text fields; the first of the text fields expects the
41  * // string "pass" as input, and will allow focus to advance out of it
42  * // only after that string is typed in by the user.
43  *
44  * public class VerifierTest extends JFrame {
45  * public VerifierTest() {
46  * JTextField tf1 = new JTextField ("Type \"pass\" here");
47  * getContentPane().add (tf1, BorderLayout.NORTH);
48  * tf1.setInputVerifier(new PassVerifier());
49  *
50  * JTextField tf2 = new JTextField ("TextField2");
51  * getContentPane().add (tf2, BorderLayout.SOUTH);
52  *
53  * WindowListener l = new WindowAdapter() {
54  * public void windowClosing(WindowEvent e) {
55  * System.exit(0);
56  * }
57  * };
58  * addWindowListener(l);
59  * }
60  *
61  * class PassVerifier extends InputVerifier {
62  * public boolean verify(JComponent input) {
63  * JTextField tf = (JTextField) input;
64  * return "pass".equals(tf.getText());
65  * }
66  * }
67  *
68  * public static void main(String[] args) {
69  * Frame f = new VerifierTest();
70  * f.pack();
71  * f.setVisible(true);
72  * }
73  * }
74  * </pre>
75  *
76  * @since 1.3
77  */
78
79
80 public abstract class InputVerifier {
81
82   /**
83    * Checks whether the JComponent's input is valid. This method should
84    * have no side effects. It returns a boolean indicating the status
85    * of the argument's input.
86    *
87    * @param input the JComponent to verify
88    * @return <code>true</code> when valid, <code>false</code> when invalid
89    * @see JComponent#setInputVerifier
90    * @see JComponent#getInputVerifier
91    *
92    */
93   
94   public abstract boolean verify(JComponent JavaDoc input);
95
96
97   /**
98    * Calls <code>verify(input)</code> to ensure that the input is valid.
99    * This method can have side effects. In particular, this method
100    * is called when the user attempts to advance focus out of the
101    * argument component into another Swing component in this window.
102    * If this method returns <code>true</code>, then the focus is transfered
103    * normally; if it returns <code>false</code>, then the focus remains in
104    * the argument component.
105    *
106    * @param input the JComponent to verify
107    * @return <code>true</code> when valid, <code>false</code> when invalid
108    * @see JComponent#setInputVerifier
109    * @see JComponent#getInputVerifier
110    *
111    */
112
113   public boolean shouldYieldFocus(JComponent JavaDoc input) {
114     return verify(input);
115   }
116
117 }
118
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