Containers

• HeavyWeight containers to contain other components
  
  • JFrame - Application base class (BorderLayout default)
    
  • Japplet - Applet base class (BorderLayout default)
    
  • Rarely used - JWindow
    
• Lightweight containers
  • JPanel - Most used (FlowLayout default)
  • JDialog
• Lightweight components extend JComponent
  • JButton, JCheckBox, JRadioButton
  • JMenuBar -> JMenu -> JMenuItem (or JCheckBoxMenuItem or JRadioButtonMenuItem)
    • Add "JRadioButtonMenuItem" objects to "ButtonGroup" object to get the only-one selection effect.

      ButtonGroup onlyOne = new ButtonGroup();
      onlyOne.add(firstButton);
      onlyOne.add(anotherButton);

    • JPopupMenu -> JMenuItem (or JCheckBoxMenuItem or JRadioButtonMenuItem)
  • JLabel, JTextField, JTextArea, JTextPane, JEditorPane
  • Jlist, JTable, JTree,
• Almost always draw on contentPane in JFrame, JApplet and JDialog objects. Use getContentPane()
• someContainer.add(someComponent)
• BoxLayout is useful, so use "Box" class. GridBagLayout is the most complex and allows the most control over component placement. Others are GridLayout and CardLayout.
• Order in which components are added to a container is important. First component added has the topmost z-order and appears first in a linear setting such as a menu list.
• Each container or component can have a custom border. Create with BorderFactory.create...() methods.

Event-Driven Graphical-User-Interface

• Since the concept is a bit abstract for people who are not used to event-driven programming, let's use a real-life analogy - Restaurant.
• Command line interface is like a SubWay fast-food restaurant...
  Wheat or White? -> 6" or 12"? -> Cheese on this? -> Which sandwich? -> What else would you like on this?
  Once you have crossed a step, it is very hard to go back to previous step (without messing up your sandwich).
• Event-driven graphical-user-interface (GUI) is like a fine dining restaurant in which yousit down and a waiter waits on you
  

  Restaurant	GUI
  Hostess seats you on a table	JFrame mainWindow = new JFrame("Your Table");
  Waiter gives you a menu	JMenuBar menuBar = new JMenuBar(); JMenu menu = new JMenu(); JMenuItem menuItem = new JMenuItem(); public class Chef implements ActionListener { public Chef(){ //Tell the "menuItem": "Add me (i.e. Chef) to your list of notifications if you are clicked" menuItem.addActionListener(this); } //When "menuItem" is clicked, Java will automatically call "Chef's" actionPerformed() method. So, Chef needs to implement that method to return useful results back to Java. void actionPerformed(ActionEvent e) { cookFood(e); } }
  You point to a menu item and say "I'll take this"	User clicks on a menu item.

• MouseEvent,WindowEvent,KeyEvent,FocusEvent
• someComponent.enableEvents(Event-Type|another-event-type|...) to enable events only if you are not using a listener but want the component to handle its own events.

    mainWindow.enableEvents(AWTEvent.WINDOW_EVENT_MASK);
  
    //In aseparate method, handle the event you are interested in
    protected void processWindowEvent(WindowEvent e)
    {
      //Only handle the WINDOW_CLOSING event
      if (e.getID() == WindowEvent.WINDOW_CLOSING)
      {
        mainWindow.dispose();                    // Release resources
        System.exit(0);               // Exit the program
      }
      //Pass the rest of the events to super class (IMPORTANT!)
      super.processWindowEvent(e);    // Pass on the event
    }
   

• someEvent.getSource() will the "Object" on which the vent occured.

  public void actionPerformed(ActionEvent e) {
  	Object source = e.getsource();
  	if (source == someMenuItem){ . . . }
  	 . . .
  }
  

• EventListener -> WindowListener, MouseInputListener (MouseListener, MouseMotionListener), KeyListener, FocusListener
  Each such listener has a number of methods to responds to all kinds of events it can listen to.
• An adapter implement a listener's blank methods so you don't have to. Just override the ones you want to implement yourself.
  WindowAdapter, MouseInputAdapter (MouseAdapter, MouseMotionAdapter), KeyAdapter, FocusAdapter
  Then, add an inner class in your application class which extends the adapter you want.
  

    mainWindow.addWindowListener(new WindowHandler());  // Add window listener
    // Separately in main class, define an inner class to handle window events
    // by extending WindowAdapter
    class WindowHandler extends WindowAdapter
    {
      // Handler for window closing event.  MAKE SURE THAT THE METHOD NAME IS SPELLED CORRECTLY
      public void windowClosing(WindowEvent e)
      {
        mainWindow.dispose();                           // Release the window resources
        System.exit(0);                             // End the application
      }
    }
   

• Buttons and menus produce ActionEvent and ItemEvent. Scrollbars produce AdjustmentEvent.
• To handle ActionEvent, implement ActionListener and define actionPerformed() method. Similar for others.
  
• "Action" interface implementing object can be added to both JMenu and JToolBar as a component. Clicking on that component will perform the same action no matter whether it is on menu or toolbar. Moreover, the same action can also be added to a popup menu
• A typical application may have between 5 and 25 Actions, and 2-3 controls per Action.
• "AbstractAction" class implements Action interface, You extend AbstractAction.
• actionObject.putValue(NAME, "text name");
actionObject.putValue(SMALL_ICON, icon-object);
actionObject.putValue(SHORT_DESCRIPTION, "text description");
actionObject.putValue(LONG_DESCRIPTION, "more text description");

• Same with getValue() methods Icon lineIcon = (Icon)actionObject.getValue(SMALL_ICON);

• Other methods are actionPerformed(), isEnabled(), setEnabled(), addPropertyChangeListener(), removePropertyChangeListener()
• Icons are typically 16x16 pixels.