Lecture 20

Menus

• Important classes are

  • JMenuBar

  • JMenu

  • JMenuItem

• all three of these are children of Component

• all implement the add() method

Creating a Menu

1. Create a Menubar

   • JMenuBar myMenuBar = new JMenuBar();

2. Create menus and add them to the menubar

   • JMenu = new JMenu(“File”);

   • MyMenuBar.add(myMenu);

3. Create and add menu items to the menu

   • JMenuItem Save = new JMenuItem(“Save”);

   • MyMenu.add(Save);

4. Add action listener to each menu item

   • Save.addActionListener(this);

5. Add menuBar to the JFrame

   • add (myMenuBar);//Bad!!

   • Set JMenuBar(myMenuBar); // Good!!

Windows and Inner Classes

• For Complicated window components it makes sense to use inner classes

Recall:

Public class OuterClass;

{

Private class InnerClass

{

}

}

• A complicated panel within a JFrame

Public class myJframe extends JFrame

{

Public myJPanel()

{//appearance of the panel;}

}

Public JFrame()

{

Add ( new myJPanel());

}

Private class myJPanel extends JPanel implements ActionListener

{

Public myJPanel()

{

JButton b = new JButton(“Button”);

b.addActionListener(this); /* this refers to myJPanel*/

add(b);

}

Public void ActionPerformed(ActionEvent e){…}

Text Field

• JTextField

  • Constructor takes an integer size argument

  • JTextField t = newJTextField(20); /* 20 chars wide*/

    • public String getText()

    • public void setText(String S)

    • public void setEditable(boolean e)