Making Applications Interactive

1

GUIs are event driven Generate events when user interacts with GUI

e.g., moving mouse, pressing button, typing in text field, etc.

2

Event source Event listener

Event object

Event handling methods

3

Object

EventObject

AWTEvent

ActionEvent

AdjustmentEvent

ItemEvent

TextEvent

ContainerEvent

FocusEvent

PaintEvent

WindowEvent

InputEvent

MouseWheelEvent

ComponentEvent

KeyEvent MouseEvent

Object

EventObject

AWTEvent

ComponentEvent

TextEvent

ItemEvent

AdjustmentEvent

ActionEvent

WindowEvent

InputEvent

MouseEventKeyEvent

MouseWheelEvent

FocusEvent

PaintEvent

ContainerEvent

4

Event-handling model Three parts

Event source GUI component with which user interacts

Event object Encapsulates information about event that occurred

Event listener Receives event object when notified, then responds

Programmer must perform two tasks Register event listener for event source Implement event-handling method (event handler)

5

interface EventListener

interface ActionListener

interface AdjustmentListener

interface ComponentListener

interface ContainerListener

interface FocusListener

interface ItemListener

interface KeyListener

interface MouseListener

interface MouseMotionListener

interface TextListener

interface WindowListener

«interface»EventListener

«interface»ActionListener

«interface»AdjustmentListener

«interface»ComponentListener

«interface»ContainerListener

«interface»FocusListener

«interface»ItemListener

«interface»KeyListener

«interface»MouseListener

«interface»MouseMotionListener

«interface»TextListener

«interface»WindowListener

6

Listener Adapter class (if any) Registration method

ActionListener addActionListener

AdjustmentListener addAdjustmentListener

ComponentListener ComponentAdapter addComponentListener

ContainerListener ContainerAdapter addContainerListener

FocusListener FocusAdapter addFocusListener

ItemListener addItemListener

KeyListener KeyAdapter addKeyListener

MouseListener MouseAdapter addMouseListener

MouseMotionListener MouseAdapter addMouseMotionListener

TextListener addTextListener

WindowListener WindowAdapter addWindowListener

7

Act that Results in the Event Listener Type

User clicks a button, presses Enter while typing in a text field, or chooses a menu item

ActionListener

User closes a frame (main window) WindowListener

User presses a mouse button while the cursor is over a component

MouseListener

User moves the mouse over a component MouseMotionListener

Component becomes visible ComponentListener

Component gets the keyboard focus FocusListener

Table or list selection changes ListSelectionListener

Any property in a component changes such as the text on a label

PropertyChangeListener

8

ActionListener Handles buttons and a few other actions

actionPerformed(ActionEvent event)

AdjustmentListener Applies to scrolling

adjustmentValueChanged(AdjustmentEvent event)

ComponentListener Handles moving/resizing/hiding GUI objects

componetResized(ComponentEvent event) componentMoved(ComponentEvent event) componentShown(ComponentEvent event) componentHidden(ComponentEvent event)

9

ContainerListener Triggered when window adds/removes GUI controls componentAdded(ContainerEvent event) componentRemoved(ContainerEvent event)

FocusListener Detects when controls get/lose keyboard focus focusGained(FocusEvent event) focusLost(FocusEvent event)

10

ItemListener Handles selections in lists, checkboxes, etc.

itemStateChanged(ItemEvent event)

KeyListener Detects keyboard events

keyPressed(KeyEvent event) – any key pressed down

keyReleased(KeyEvent event) – any key released keyTyped(KeyEvent event) – key for printable char

released

11

MouseListener Applies to basic mouse events

mouseEntered(MouseEvent event) mouseExited(MouseEvent event) mousePressed(MouseEvent event) mouseReleased(MouseEvent event) mouseClicked(MouseEvent event) – release

without drag Applies on release if no movement since pressed

MouseMotionListener Handles mouse movement

mouseMoved(MouseEvent event) mouseDragged(MouseEvent event)

12

TextListener Applies to textfields and text areas

textValuedChanged(TextEvent event)

WindowListener Handles high-level window events

windowOpened, windowClosing, windowClosed, windowIconified, windowDeiconified, windowActivated, windowDeactivated

13

Button ActionListener

ActionEvent

actionPerformed(..)

14

o is an event sourceh is an event listener of type XXX

o.addXXX(h)

where XXX is one of the following:

ActionListener

MouseListener

MouseMotionListener

KeyListener

WindowListener

ComponentListener

FocusListener

TextListener

AdjustmentListener

ItemListener15

interface ActionListener {

public void actionPerformed(ActionEvent e);

} Possible event sources

Button List TextField MenuItem

16

import javax.swing.*;import java.awt.event.*;public class TestButtonAction { public static void main(String[] args){ JFrame f = new JFrame("TestButton"); f.setSize(200,200); JButton hw = new JButton("Hello World!"); f.add(hw); hw.addActionListener(new ActionListener(){ public void actionPerformed(ActionEvent e){

System.exit(0); } }); f.setVisible(true); }}

17

18

class MyFrame extends JFrame implements ActionListener { Button hw; public MyFrame(){

super("Test Button");setSize(200,200);hw = new Button("Hello World!");add(hw);hw.addActionListener(this);setVisible(true);

} public void actionPerformed(ActionEvent o){

System.exit(0); }}

19

class MyFrame extends JFrame { Button hw; public MyFrame(){

super("Test Button");setSize(200,200);hw = new Button("Hello World!");add(hw);hw.addActionListener(new MyActionListener());setVisible(true);

 //Inner classclass MyActionListener implements ActionListener{

public void actionPerformed(ActionEvent o){System.exit(0);

}}

}}