Graphical User Interface (GUI) - 2

Graphical User
Interface (GUI) II

Objectives
 Differentiate the use of event handling for each
component.
 Apply appropriate event handling based on
given problem.
 Transform program from java application to
java applet and vice versa.

Event-Driven Programming
 In event-driven programming, code is executed upon
activation of events.
 Ex: a button click, or mouse movement
3

Events and Event Source
 An event can be defined as a type of signal to the
program that something has happened.
 The event is generated by external user actions such as
mouse movements, mouse button clicks, and
keystrokes, or by the operating system, such as a timer.
 The component on which an event is generated is called
the source object.
 Ex: source object: Button for a button-clicking action event.
4

Event Classes
Subclasses an event is an object of the EventObject class

Event Information
 An event object contains whatever properties are pertinent
to the event.
 You can identify the source object of the event using the
getSource() instance method in the EventObject class.
 The subclasses of EventObject deal with special types of
events, such as button actions, window events, component
events, mouse movements, and keystrokes.
6

Selected User Actions
7
Source Event Type
User Action Object Generated
Click a button JButton ActionEvent
Click a check box JCheckBox ItemEvent, ActionEvent
Click a radio button JRadioButton ItemEvent, ActionEvent
Press Enter on a text field JTextField ActionEvent
Select a new item JComboBox ItemEvent, ActionEvent
Select item(s) JList ListSelectionEvent
Select a menu item JMenuItem ActionEvent
Window opened, closed, etc. Window WindowEvent
Mouse pressed, released, etc. Component MouseEvent
Key released, pressed, etc. Component KeyEvent
In detail, refer to Table 16.1 pg 559

Listeners, Registartions, and
Handling Events
 Java uses a delegation-based model for event
handling
 An external user action on a source object triggers an event
 An object interested in the event receives the event
 The latter object is called a listener
8

Listeners, Registrations, and
Handling Events
 Two things are needed for an object to be a listener for an event on
a source object:
1. The listener object’s class must implement the corresponding event-
listener interface. Java provides a listener interface for every type of
GUI event.
The listener interface is usually named XListener for XEvent ,
Ex: Listener interface for ActionEvent is ActionListener
each listener for ActionEvent should implement the ActionListener
interface
9

Selected Event Handlers
10
Event Class Listener Interface Listener Methods (Handlers)
ActionEvent ActionListener actionPerformed(ActionEvent)
ItemEvent ItemListener itemStateChanged(ItemEvent)
WindowEvent WindowListener windowClosing(WindowEvent)
windowOpened(WindowEvent)
windowIconified(WindowEvent)
windowDeiconified(WindowEvent)
windowClosed(WindowEvent)
windowActivated(WindowEvent)
windowDeactivated(WindowEvent)
ContainerEvent ContainerListener componentAdded(ContainerEvent)
componentRemoved(ContainerEvent)
MouseEvent MouseListener mousePressed(MouseEvent)
mouseReleased(MouseEvent)
mouseClicked(MouseEvent)
mouseExited(MouseEvent)
mouseEntered(MouseEvent)
KeyEvent KeyListener keyPressed(KeyEvent)
keyReleased(KeyEvent)
keyTypeed(KeyEvent)
In detail, refer to Table 16.2 pg 561

Handling Events
 Two things are needed for an object to be a listener for an event on
a source object:
2. The listener object must be registered by the source object. Registration
methods are dependent on the event type
Ex: For ActionEvent, the method is addActionListener
In general: the method is named addXListener for XEvent
11

Handling Events
 For each event, the source object maintains a list of listeners and
notifies all the registered listeners by invoking the handler on the
listener object to respond to the event.
12

The Delegation Model: Example
13
source: JButton
+addActionListener(ActionListener listener)
listener: ListenerClass
ActionListener
+actionPerformed(ActionEvent event)
Register by invoking
source.addActionListener(listener);
ListenerClass listener = new ListenerClass();
JButton jbt = new JButton("OK");
jbt.addActionListener(listener);
class ListenerClass implements ActionListener {
public void actionPerformed(ActionEvent e) {
S.o.p (“Button “+ e.getActionCommand()+ “ is
clicked.”);}

Example:
 Class must implement the listener interface (ex: ActionListener).
and method to handle the event (ex: actionPerformed())
 The listener object must register with source object (ex: button)
 Done by invoking the addActionListener in the button object
 Ex::
public class TestActionButton extends JFrame implements ActionListener
{
JButton btn = new JButton(“Click Here");
btn.addActionListener(this);
public void actionPerformed(ActionEvent e)
{
}
}
Registration method (XEvent  addXListener)

ActionEvent
 The components that involved with this event are:
 JButton – clicka a button
 JMenuItem – select a menu item
 JTextField – press return on a text field
 Event listener interface – ActionListener
 Event handler method

java.awt.event.ActionEvent
16
java.awt.event.ActionEvent
+getActionCommand(): String
+getModifier(): int
+getWhen(): long
Returns the command string associated with this action. For a
button, its text is the command string.
Returns the modifier keys held down during this action event.
Returns the timestamp when this event occurred. The time is
the number of milliseconds since January 1, 1970, 00:00:00
GMT.
java.util.EventObject
+getSource(): Object Returns the object on which the event initially occurred.
java.awt.event.AWTEvent

import java.awt.*;
import javax.swing.*;
import java.awt.event.*;
public class UjiActionButang extends JFrame implements ActionListener
{
JButton btg = new JButton("Sila Klik");
JTextField txtField = new JTextField(10);
JLabel lbl = new JLabel(" ");
public UjiActionButang()
{
super("Melaksanakan ActionEvent");
Container bekas = getContentPane();
bekas.setLayout(new FlowLayout());
bekas.add(btg);
btg.addActionListener(this);
bekas.add(txtField);
bekas.add(lbl);
setSize(300,200);
setVisible(true);
}
{
if (e.getSource()== btg)
{
lbl.setText("Terima Kasih");
txtField.setText("Sama-sama");
}
}
public static void main(String[] arg)
{
UjiActionButang teks = new UjiActionButang();
teks.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
}
}
To display label, and text on text field
when button is clicked

import java.awt.*;
public class ActionTextField extends JFrame implements ActionListener
{
JLabel lbl = new JLabel("Nama ");
public ActionTextField()
{
super("Melaksanakan ActionEvent- TextField");
bekas.add(lbl);
txtField.addActionListener(this);
setSize(300,200);
setVisible(true);
}
{
if (e.getSource()== txtField)
{
JOptionPane.showMessageDialog(this,"Nama anda = "+
txtField.getText(),"Pemberitahuan",
JOptionPane.INFORMATION_MESSAGE);
}
}
{
ActionTextField teks = new ActionTextField();
}
}
To display name from text field on dialog
box
when pressing <enter> on text field

import java.awt.*;
public class ActionButton extends JFrame implements ActionListener
{
JLabel lbl = new JLabel("Nama ");
JButton btg = new JButton("Klik");
JTextArea txtArea = new JTextArea("Ali",10,6);
public ActionButton()
{
super("Melaksanakan ActionEvent- Butang");
bekas.add(lbl);
bekas.add(btg);
bekas.add(txtArea);
setSize(300,200);
setVisible(true);
}
{
{
txtArea.append("n"+txtField.getText());
}
}
{
ActionButton teks = new ActionButton();
}
}
To append text on text area when button is
clicked

import java.awt.*;
public class UjiActionMenu extends JFrame implements ActionListener
{
JFrame frame = new JFrame();
JMenuBar jmb = new JMenuBar();
JMenu fileMenu = new JMenu("File");
JMenuItem baru= new JMenuItem("New");
JMenuItem buka= new JMenuItem("Open");
public UjiActionMenu()
{
frame.setTitle("membuat menu");
baru.addActionListener(this);
fileMenu.add(baru);
fileMenu.add(buka);
jmb.add(fileMenu);
frame.setJMenuBar(jmb);
frame.setSize(400,200);
frame.setVisible(true);
}
{
if (e.getSource() == baru)
JOptionPane.showMessageDialog(this,"Anda telah memilih menu New",
"Pemberitahuan",JOptionPane.INFORMATION_MESSAGE);
}
{
UjiActionMenu teks = new UjiActionMenu();
}
}
Display dialog box when menu item is clicked

comboBox
 Generate two types of event
 ActionEvent
 ItemEvent
 For the case of ItemEvent:
 Event listener Interface : ItemListener
 Event handler method
 public void ItemStateChanged(ItemEvent e)
○ When select an item in the combo box
 Index for the first item in the combo box will be started
by 0..n-1.

comboBox
javax.swing.JComboBox
+JComboBox()
+JComboBox(items: Object[])
+addItem(item: Object): void
+getItemAt(index: int): Object
+getItemCount(): int
+getSelectedIndex(): int
+setSelectedIndex(index: int): void
+getSelectedItem(): Object
+setSelectedItem(item: Object): void
+removeItem(anObject: Object): void
+removeItemAt(anIndex: int): void
+removeAllItems(): void
Creates a default empty combo box.
Creates a combo box that contains the elements in the specified array.
Adds an item to the combo box.
Returns the item at the specified index.
Returns the number of items in the combo box.
Returns the index of the selected item.
Sets the selected index in the combo box.
Returns the selected item.
Sets the selected item in the combo box.
Removes an item from the item list.
Removes the item at the specified index in the combo box.
Removes all items in the combo box.
javax.swing.JComponent
22

Using the
itemStateChanged Handler
public void itemStateChanged(ItemEvent e)
{
// Make sure the source is a combo box
if (e.getSource() instanceof JComboBox)
String s = (String)e.getItem();
}
23
When a new item is selected, itemStateChanged() for
ItemEvent is invoked .

import java.awt.*;
public class UjiItemEventComboBox extends JFrame
implements ItemListener
{
JComboBox jcb = new JComboBox();
public UjiItemEventComboBox()
{
super("Membuat combobox");
jcb.addItem("wira");
jcb.addItem("waja");
jcb.addItemListener(this);
bekas.add(jcb);
setSize(400,200);
setVisible(true);
}
{
if (e.getSource()== jcb)
{
if (e.getStateChange() == ItemEvent.SELECTED)
{
String s1 = (String) jcb.getSelectedItem();
JOptionPane.showMessageDialog(this,"Anda telah memilih "+s1,"Maklumat",
}
}
}
ItemEvent: Display item on dialog box when
item in Combo Box is selected

{
UjiItemEventComboBox teks = new UjiItemEventComboBox();
}
}

import java.awt.*;
public class UjiActionEventComboBox extends JFrame implements ActionListener
{
JComboBox jcb = new JComboBox();
public UjiActionEventComboBox()
{
super("Membuat combobox");
jcb.addItem("wira");
jcb.addItem("waja");
bekas.add(jcb);
bekas.add(btg);
setSize(400,200);
setVisible(true);
}
{
{
String s1 = (String)jcb.getSelectedItem();
JOptionPane.showMessageDialog(this,"Anda telah memilih "+s1,“
Maklumat",JOptionPane.INFORMATION_MESSAGE);
}
}
{
UjiActionEventComboBox teks = new UjiActionEventComboBox();
}
ActionEvent: Display selected item on dialog
box when a button is clicked

ListSelectionEvent -
JList Generates javax.swing.event.ListSelectionEvent to notify the
listeners of the slections
 Event listener interface : ListSelectionListener
 Event handler interface:
public void valueChanged(ListSelectionEvent e)
○ When select item(s) in JList
 Index for the first item in the JList will be started by
0..n-1.

ListSelectionEvent - JList
javax.swing.JList
+JList()
+JList(items: Object[])
+getSelectedIndex(): int
+setSelectedIndex(index: int): void
+getSelectedIndices(): int[]
+setSelectedIndices(indices: int[]): void
+getSelectedValue(): Object
+getSelectedValues(): Object[]
+getVisibleRowCount(): int
+setVisibleRowCount(count: int): void
+getSelectionBackground(): Color
+setSelectionBackground(c: Color): void
+getSelectionForeground(): Color
+setSelectionForeground(c: Color): void
+getSelectionMode(): int
+setSelectionMode(selectionMode: int):
Creates a default empty list.
Creates a list that contains the elements in the specified array.
Returns the index of the first selected item.
Selects the cell at the specified index.
Returns an array of all of the selected indices in increasing order.
Selects the cells at the specified indices.
Returns the first selected item in the list.
Returns an array of the values for the selected cells in increasing index order.
Returns the number of visible rows displayed without a scrollbar. (default: 8)
Sets the preferred number of visible rows displayed without a scrollbar.
Returns the background color of the selected cells.
Sets the background color of the selected cells.
Returns the foreground color of the selected cells.
Sets the foreground color of the selected cells.
Returns the selection mode for the list.
Sets the selection mode for the list.
javax.swing.JComponent
28

import java.awt.*;
import javax.swing.event.*;
class UjiSelectionEventList extends JFrame implements ListSelectionListener
{
String[] jenisWarna= {"merah","hijau","kuning","jingga","biru"};
JList senaraiWarna;
public UjiSelectionEventList()
{
super("Membuat JList");
senaraiWarna = new JList(jenisWarna);
senaraiWarna.addListSelectionListener(this);
senaraiWarna.setVisibleRowCount(3);
senaraiWarna.setSelectionMode(ListSelectionModel.SINGLE_SELECTION);
bekas.add(new JScrollPane(senaraiWarna));
setSize(300,200);
setVisible(true);
}
public void valueChanged(ListSelectionEvent e)
{
if (e.getSource()== senaraiWarna)
{
String s1 = (String)senaraiWarna.getSelectedValue();
JOptionPane.showMessageDialog(this,s1,"maklumat",
}
}
SelectionEvent: Display selected item when
item in JList is clicked

{
UjiSelectionEventList list = new UjiSelectionEventList();
list.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
}
}

import java.awt.*;
import javax.swing.event.*;
class DataListEventt extends JFrame implements ActionListener
{
String[] jenisWarna= {"merah","hijau","kuning","jingga","biru"};
JList senaraiWarna;
public DataListEventt()
{
super("Membuat JList");
senaraiWarna = new JList(jenisWarna);
senaraiWarna.setVisibleRowCount(3);
senaraiWarna.setSelectionMode(ListSelectionModel.SINGLE_SELECTION);
bekas.add(new JScrollPane(senaraiWarna));
bekas.add(btg);
setSize(300,200);
setVisible(true);
}
{
{
String s1 = (String)senaraiWarna.getSelectedValue();
JOptionPane.showMessageDialog(this,s1,"maklumat",
}
}
ActionEvent: Display selected item in JList
when a button is clicked

{
DataListEventt list = new DataListEventt();
list.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
}
}

ItemEvent -
RadioButton Event Listener Interface : ItemListener
 Event handler method :
○ Click a radio button

import java.awt.*;
public class UjiItemListenerRadioButton extends JFrame implements ItemListener
{
JRadioButton rdButton1,rdButton2;
public UjiItemListenerRadioButton()
{
super("Membuat RadioButton");
rdButton1 = new JRadioButton("wira");
rdButton2 = new JRadioButton("Waja",true);
rdButton1.addItemListener(this);
rdButton2.addItemListener(this);
bekas.add(rdButton1);
ButtonGroup butang = new ButtonGroup();
butang.add(rdButton1);
setSize(400,200);
setVisible(true);
}
ItemEvent: Display item on dialog box when a
radio button is clicked

{
if (e.getSource()== rdButton1)
{
JOptionPane.showMessageDialog(this,"kereta wira","Maklumat",
}
if (e.getSource()== rdButton2)
{
JOptionPane.showMessageDialog(this,"kereta waja","Maklumat",
}
}
{
UjiItemListenerRadioButton teks = new UjiItemListenerRadioButton();
}
}

import java.awt.*;
public class DataRadioButton extends JFrame implements ActionListener
{
JRadioButton rdButton1,rdButton2;
String kereta;
public DataRadioButton()
{
super("Membuat RadioButton");
rdButton1 = new JRadioButton("wira");
rdButton2 = new JRadioButton("Waja",true);
bekas.add(btg);
ButtonGroup butang = new ButtonGroup();
setSize(400,200);
setVisible(true);
}
ActionEvent: Display selected item from
radio button when a button is clicked

{
{
if (rdButton1.isSelected())
kereta = "Wira";
if (rdButton2.isSelected())
kereta = "Waja";
JOptionPane.showMessageDialog(this,kereta,"maklumat",
}
}
{
DataRadioButton teks = new DataRadioButton();
}
}

ItemEvent - CheckBox
 Event Listener Interface : ItemListener
 Event handler metod :
○ Click a check box

import java.awt.*;
public class UjiItemEventCheckBox extends JFrame implements ItemListener
{
JCheckBox chkBox1,chkBox2;
public UjiItemEventCheckBox()
{
super("Membuat CheckBox");
chkBox1 = new JCheckBox("Wira");
chkBox1.addItemListener(this);
chkBox2 = new JCheckBox("Waja");
bekas.add(chkBox1);
bekas.add(chkBox2);
setSize(400,200);
setVisible(true);
}
{
if (e.getSource()== chkBox1)
{
JOptionPane.showMessageDialog(this,"Di tanda","Maklumat",
}
}
{
UjiItemEventCheckBox teks = new UjiItemEventCheckBox();
}
}
ItemEvent: Display a message when clicking a
check box

import java.awt.*;
public class DataCheckBox extends JFrame implements ActionListener
{
JCheckBox chkBox1,chkBox2;
String kereta;
public DataCheckBox()
{
super("Membuat CheckBox");
chkBox1 = new JCheckBox("Wira");
chkBox2 = new JCheckBox("Waja");
bekas.add(chkBox1);
bekas.add(chkBox2);
bekas.add(btg);
setSize(400,200);
setVisible(true);
}
ActionEvent: Display selected item from
check box when button is clicked

{
{
if (chkBox1.isSelected())
kereta = "Wira";
if (chkBox2.isSelected())
kereta = "Waja";
JOptionPane.showMessageDialog(this,kereta,"maklumat",
}
}
{
DataCheckBox teks = new DataCheckBox();
}
}

Graphical User Interface (GUI) - 2

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