Name: stC104175 Date: 05/31/2000


(see also 4286708)

java version "1.3.0rc1"
Java(TM) 2 Runtime Environment, Standard Edition (build 1.3.0rc1-T)
Java HotSpot(TM) Client VM (build 1.3.0rc1-S, mixed mode)

Research
The code matches the documentation in the fact that _focus_ is not transferred
to another swing component that requests it when shouldYieldFocus() returns
false.

Testing
However, during my testing, I have found that even though shouldYieldFocus()
returns false, the _actionPerformed()_ event (or valueChanged() event or
propertyChanged() event, depending on Swing component requesting focus) is sent
to the swing component requesting focus!

This event handler has no idea about the invalid entry.

Example:
In the windows explorer, rename a file (without hitting enter) and place a
vertical bar (or any illegal filename char) in the file name. (If you don't have
a windows box, please forgive me --- perhaps your SUN box has a similar file
manager application.) Now click any other tree item in the tree control on the
left hand side in order to change the folder selection. The windows explorer
displays and error message that says you've entered an invalid file name. The
tree item selection has not changed.

Observation
If the windows explorer were written in kestrel using the new InputVerifier
class, the tree selection would change while keeping focus in the component
containing invalid file name with the vertical bar.

Conclusion
The tree selection event would result in the "explorer written in swing" app
hiding the component containing the invalid file name and displaying a component
listing files associated with the folder selected in the tree control!

Question
How can I prevent the actionPerformed event (or valueChanged() event or
propertyChanged() event, depending on Swing component requesting focus) from
being sent to a Swing component when the component containing input focus
contains invalid data?

------code below-------
import java.awt.*;
import java.util.*;
import java.awt.event.*;
import javax.swing.*;
import java.beans.*;
import javax.swing.event.*;
 
 // 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
{
  JTextField jTextField1 = new JTextField();
  JTextField jTextField2 = new JTextField();
  JTree jTree1 = new JTree();

 public VerifierTest ()
 {
   addWindowListener (new MyWAdapter ());

    try
    {
      jbInit();
    }
    catch(Exception e)
    {
      e.printStackTrace();
    }
 }

  public static void main (String [] args)
  {
    Frame f = new VerifierTest ();
    f.pack();
    f.show();
  }

  class MyWAdapter extends WindowAdapter
  {
    public void windowClosing(WindowEvent event)
    {
      System.exit (0);
    }
  }

  class PassVerifier extends InputVerifier
  {
    public boolean verify(JComponent input)
    {
      JTextField tf = (JTextField) input;
      String pass = tf.getText();

      boolean bRet = false;

      if (pass.equals("pass"))
         bRet = true;

System.out.println("#verify <" + pass + ">, boolean = " + bRet );

      return bRet;
    }

    public boolean shouldYieldFocus(JComponent input)
    {
      JTextField tf = (JTextField) input;
      String pass = tf.getText();
      boolean bRet = false;

      if (pass.equals("pass"))
         bRet = true;

System.out.println("#shouldYieldFocus <" + pass + ">, boolean = " + bRet );

      return bRet;
    }
  }

  private void jbInit() throws Exception
  {
    jTextField1.setText("jTextField1");
    jTextField2.setText("jTextField2");

    jTextField1.addFocusListener(new java.awt.event.FocusAdapter()
    {
      public void focusGained(FocusEvent e)
      {
        jTextField1_focusGained(e);
      }
    });

    jTextField2.addFocusListener(new java.awt.event.FocusAdapter()
    {
      public void focusGained(FocusEvent e)
      {
        jTextField2_focusGained(e);
      }
    });

    jTree1.addTreeSelectionListener(new
javax.swing.event.TreeSelectionListener() {

      public void valueChanged(TreeSelectionEvent e) {
        jTree1_valueChanged(e);
      }
    });
    jTree1.addPropertyChangeListener(new java.beans.PropertyChangeListener() {

      public void propertyChange(PropertyChangeEvent e) {
        jTree1_propertyChange(e);
      }
    });
    this.getContentPane().add(jTextField1, BorderLayout.CENTER);
    this.getContentPane().add(jTextField2, BorderLayout.SOUTH);
    this.getContentPane().add(jTree1, BorderLayout.WEST);

    jTextField1.setInputVerifier(new PassVerifier());
    jTextField2.setInputVerifier(new PassVerifier());
  }

  void jTextField1_focusGained(FocusEvent e)
  {
System.out.println("jTextField1 focusGained");
  }

  void jTextField2_focusGained(FocusEvent e)
  {
System.out.println("jTextField2 focusGained");
  }

  void jTree1_valueChanged(TreeSelectionEvent e)
  {
System.out.println("jTree1_valueChanged");
  }

  void jTree1_propertyChange(PropertyChangeEvent e)
  {
System.out.println("jTree1_propertyChange");
  }
}
(Review ID: 101342)
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