textlistenerdemo.java

来自「java 完全探索的随书源码」· Java 代码 · 共 43 行

// TextListenerDemo.java

import java.awt.*;
import java.awt.event.*;

class TextListenerDemo extends Frame implements TextListener
{
   TextListenerDemo (String title)
   {
      super (title);

      Panel p = new Panel ();
      p.setLayout (new FlowLayout (FlowLayout.LEFT));
      p.add (new Label ("Please enter a name (8 chars maximum):"));
      TextField nameField = new TextField (10);
      nameField.addTextListener (this);
      p.add (nameField);
      add (p, "North");

      setSize (400, 100);

      setVisible (true);
   }

   public void textValueChanged (TextEvent e)
   {
      TextField tf = (TextField) e.getSource ();
      String text = tf.getText ();

      if (text.length () > 8)
      {
          int cp = tf.getCaretPosition ();
          tf.setText (text.substring (0, text.length () - 1));
          tf.setCaretPosition (cp);
      }
   }

   public static void main (String [] args)
   {
      new TextListenerDemo ("Text Listener Demo");
   }
}