CS1054: Lecture 21 - Graphical User Interface

Graphical User Interfaces vs. Text User Interface

Three steps to GUI Programming What kind of elements can we show on screen? Components How do we arrange those elements? Layout How do we react to user input? Event Handlers

AWT vs SWING Java has two GUI libraries – AWT and Swing Swing later and much improved than AWT Equivalent classes in Swing can be identified by a J at the start of class name.

Top level Window In control of Operating System’s window management Java word – Frames Swing calls - JFrame

JFrame Windows Title bar Menu bar Content pane

Adding Simple Components JLabel frame.pack( ); frame.setVisible (true);

Adding Menus JMenuBar JMenu JMenuItem

Creating Menubars – 3 steps JMenuBar menubar = new JMenuBar ( ); frame.setJMenuBar ( menubar ); JMenu fileMenu = new JMenu ( “File”); menubar.add (fileMenu); JMenuItem openItem = new JMenuItem (“Open”); fileMenu.add (openItem); JMenuItem quitItem = new JMenuItem (“Quit”); fileMenu.add (quitItem);

Event Handling ActionEvent MouseEvent WindowEvent

To receive events 1. import java.awt.event.*; 2. To class header ActionListener interface 3. public void actionPerformed (ActionEvent event) 4. The objects must call addActionListener ( ) to register as a listener

Add ActionListener public class ImageViewer implements ActionListener public void actionPerformed (ActionEvent event) { System.out.println ("Item: " + event.getActionCommand ( )); } openItem.addActionListener( this); quitItem.addActionListener( this);

Layout Managers - Arrange components on a screen. - Each container has a Layout Manager associated with it. - The Layout Manager takes care of arranging components within that container

Layout Managers iswing/layout/visual.html -FlowLayout - BorderLayout - GridLayout

MouseListener Demo /java/awt/event/MouseListener.html