21. ActionListener interface

• ActionListener interface specifies the

  
      actionPerformed( ActionEvent evt );
  
  

  method. The implementation can execute any statements in response to the event.

• The actionPerformed() is invoked when the user

  • clicks a button

  • chooses a menu item

• Note: When more than one component is added to the JFrame, it is necessary to find out which component is the source of the event:

  
      /** 
      * Handles user clicks
      */
      public void actionPerformed( ActionEvent event )
      {
          Object obj = event.getSource();
          if ( obj == mButton )
          {
              mButton.setText( "Click!" );
          }
      }