Re: Action Listeners for JTextFields

From:

"Andrew Thompson" <u32984@uwe>

Newsgroups:

comp.lang.java.programmer

Date:

Mon, 15 Oct 2007 15:02:36 GMT

Message-ID:

<79bb6a05f1479@uwe>

Some other variants to consider..

<sscce>
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;

class Test2 extends JFrame implements ActionListener {

  // scope class..
  JTextField jtf = new JTextField(20);

  Test2() {
    JPanel p1 = new JPanel();
    p1.add(jtf);
    // layout constraint
    this.add(p1, BorderLayout.NORTH);
    JButton jb = new JButton("Click Me!");
    // layout constraint
    this.add(jb, BorderLayout.CENTER);
    jb.addActionListener(this);
  }

  /** The action listener is implemented as follows */
  public void actionPerformed(ActionEvent e){
    System.out.println(jtf.getText());
  }

  /** Add a simple main to throw it on-screen */
  public static void main(String[] args) {
    Runnable r = new Runnable() {
      public void run() {
        Test2 test = new Test2();
        test.setDefaultCloseOperation(
          JFrame.EXIT_ON_CLOSE);
        test.pack();
        test.setVisible(true);
      }
    };
    SwingUtilities.invokeLater(r);
  }
}
</sscce>

..and..

<sscce>
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;

class Test3 extends JFrame {

  Test3() {
    JPanel p1 = new JPanel();
    // scope local, must be final..
    final JTextField jtf = new JTextField(20);
    p1.add(jtf);
    // layout constraint
    this.add(p1, BorderLayout.NORTH);
    JButton jb = new JButton("Click Me!");
    // layout constraint
    this.add(jb, BorderLayout.CENTER);
    //jb.addActionListener(this);
    // implement actionlistener as inner class
    jb.addActionListener(
      new ActionListener(){
        /** The action listener is implemented as follows */
        public void actionPerformed(ActionEvent e){
          System.out.println(jtf.getText());
        }
      });
  }

  /** Add a simple main to throw it on-screen */
  public static void main(String[] args) {
    Runnable r = new Runnable() {
      public void run() {
        Test3 test = new Test3();
        test.setDefaultCloseOperation(
          JFrame.EXIT_ON_CLOSE);
        test.pack();
        test.setVisible(true);
      }
    };
    SwingUtilities.invokeLater(r);
  }
}
</sscce>

HTH

--
Andrew Thompson
http://www.athompson.info/andrew/

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