JAVA UNIT 5.pptx jejsjdkkdkdkjjndjfjfkfjfnfn

Event Handling and Swings
Event Handling
1) Two Event Handling Mechanisms
2) The Delegation Event Model
a. Events
b. Event Sources
c. Event Listeners
3) Event Classes
4) Sources of Events
5) Event Listener Interfaces
6) Adapter Classes
Swings
1) The Origin of Swing
2) Swing is built on the AWT
3) Two Key Features of Swing
4) Swing Components and Containers
5) A Simple Swing Application
6) Event Handling
7) Create a Swing Applet
8) Exploring Swing

Two Event Handling Mechanisms
 Event is the change in the state of the object or source. Events are generated as
result of user interaction with the graphical user interface components.
 For example, clicking on a button, moving the mouse, entering a character
through keyboard, selecting an item from list, scrolling the page are the
activities that causes an event to happen.
 Event Handling is the mechanism that controls the event and decides what
should happen if an event occurs. This mechanism have the code which is
known as event handler that is executed when an event occurs.
 The Way in which events are handled changed significantly between the
original version of java i.e 1.0 and modern versions of java. The Modern
approach is called the Delegation Event Model.
 This model defines the standard mechanism to generate and handle the events.

The Delegation Event Model has the following key participants
namely
Source- The source is an object on which event occurs. Source is
responsible for providing information of the occurred event to its
handler. Java provide us with classes for source object.
Listener - It is also known as event handler. Listener is responsible
for generating response to an event. From java implementation point
of view the listener is also an object. Listener waits until it receives an
event. Once the event is received, the listener process the event then
returns.

 The Modern approach to handling events is based on the delegation event model, which
defines standard and consistent mechanisms to generate and process events.
 A source generates an event and sends it to one or more listeners.
 In this schema, the listener simply waits until it receives an event. Once an event is
received, the listener processes the event and then returns.
 The advantage of this design is that the application logic that processes events is cleanly
separated from the user interface logic that generates those events.
 A User interface element is able to “delegate” the processing of an event to a separate
piece of code.
 In the delegation Event model, listeners must register with a source in order to receive an
event notification.
 This provides an important benefit notifications are sent only to listeners that want or
receive them.
 This is a more efficient want to handle events than the design used by the old java 1.0
approach.

 In this model, there is a source, which generates events.
 There is a Listener, which can listen to the happenings of an event and initiate
an action.
 A Listener has to register with a source.
 When an event takes place, it is notified to the listeners, which are registered
with the source.
 The Listener then initiates an action.

Event Classes
The Classes that represent events are called Event Classes.
EVENT CLASS DESCRIPTION
ActionEvent Generates when a Button is pressed, a List item is double_clicked, or a Menu
item is selected.
ItemEvent Generated when a check box or list item is clicked
Also occurs when a choice selection is made or a checkable MenuItem is
selected or deselected.
TextEvent Generated when the value of a TextArea or TextField is changed.
AdujustementEvent Generated when a ScrollBar is manipulated
ContainerEvent Generated when a component is added to or removed form a container.
KeyEvent Generated when inpur is received form the keyboard.
FocusEvent Generated when a component gains or loses keyboard focus.

Sources of Events
 An Event sources is a GUI Object which generates Events.
 Buttons, ListBoxes and Menus etc., are common Event sources in GUI based
applications. (or)
 The Graphical User Interface Components that generates the Events are called Event
Sources.
 Some of the User Interface Components that can generate Events are
EVENT SOURCE DESCRIPTION
Button Generates Action Events when the Button is Pressed
CheckBox Generates Item Events when the checkbox is Selected or Deselected.
Choice Generates Item Events when the choice is changed.
List Generates Action Events when an item is DoubleClicked.
Generates Item Events when a Item is Selected or Deselected.
MenuItem Generates Action Events when an Menu item is Selected.
Generates Item Events when a Checkable Menu Item is Selected and
Deselected.
ScrollBar Generates Adjustment Events when the scroll bar is manipulated.
TextComponent Generates text events when the user enters a character.
Window Generates window Events when a window is activated, closed, deactivated,
deiconified, iconified, opened or quit.

EVENT LISTENER
 When an Event occurs, the event source invokes the appropriate method defined by the
listener and provides an event object as its argument.
 The below table lists commonly used listener interfaces and provides a brief description of
methods that they define.
INTERFACE DESCRIPTION
ActionListener Defines one method to receive action events
ItemListener Defines one method to recognize when the state of an item
changes.
TextListener Defines one method to recognize when a text value changes.
AdjustementListener Defines one method to receive adjustment event.
ContainerListener Defines two method to recognize when a component is added
to or removed from a container.
KeyListener Defines three methods to recognize when a key is pressed,
released, or typed.
FocusListener Defines two methods to recognize when a component gains or
losses keyboard focus.

EVENT SOURCE EVENT CLASS EVENT LISTENER METHODS IN LISTENER
INTERFACE
Button Clicked
MenuItem
Selected
ActionEvent ActionListener void actionPerformed(ActionEvent ae)
Combo box item selected ActionEvent
ItemEvent
Action Listener
ItemListener
void actionPerformed(ActionEvent ae) void
itemStateChanged(ItemEvent ie)
List Item Selected ListSelectionE vent ListSelectionListene r void valueChanged(ListSelectionEvent le)
RadioButton Selected ActionEvent
ItemEvent
Action Listener
ItemListener
Check Box Selected ActionEvent
ItemEvent
Action Listener
ItemListener
Scroll Bar Repositioned AdjustmentEve nt AdustmentListener void
adjustmentValueeChanged(AdjustmetEvent ae)
Window Changed WindowEvent WindowListener void windowAcitivated(WindowEvent we) void
windowClosed(WindowEvent we) void windowClosing(WindowEvent we)
void windowdeactivated(WindowEvent we) void
windowDeiconified(WindowEvent we) void
windowIconified(WindowEvent we) void windowOpened(WindowEvent
we)
Focus Changed FocusEvent FocusListener void focusLost(FocusEvent fe) void focusGain(FocusEvent fe)
Key Pressed KeyEvent KeyListener void keyPressed(KeyEvent ke) void keyReleased(KeyEven tke)
void keyTyped(KeyEvent ke)
Mouse clicked MouseEvent MouseListener void mouseClicked(MouseEvent me) void mouseEntered(MouseEvent
me) void mouseExited(MouseEvent me)

Adapter Classes
Adapter Class Listener Interface
ComponentAdapter ComponentListener
CaontainerAdapter ContainerListener
FocusAdapter FocusListener
KeyAdapter KeyListener
MouseAdapter MousrListener
MouseMotionAdapter MouseMotionListener
WindowAdapter WindowListener
• An Adapter class provides an empty implementation of all methods in an
event listener interface.
• Adapter classes are useful when you want to receive and process only some of
the events that are handled by a particular event listener interface.
• Commonly used Listener interfaces implemented by Adapter Classes are

SWING
1) The Origin of Swing
2) Swing is built on the AWT
3) Two Key Features of Swing
4) Swing Components and Containers
6) Event Handling
7) Create a Swing Applet
8) Exploring Swing

1) The origin of swing
 Swing is a set of classes that provide more powerful and flexible GUI Components than
AWT(Abstract Window Toolkit).
 Swing is a package which contains classes related to graphical components like
text box, check box, radio button etc…
 awt (abstract window toolkit) is also such package.
 So, awt and swing both are packages which contain classes for creating
Graphical User Interface .
 The appearance of graphical components , that are created using awt package
will not look consistent because the look and feel of the components depends
on the os on which the application is executed.
 To overcome this limitation, java soft people introduced swing package ,
through which the components look and feel does not vary from os to os.

2) SWING IS BUILT ON THE AWT
 Although Swing eliminates a number of limitations inherent in the AWT, swing
does not replace it.
 Instead, swing is built on the foundation of AWT. This is the reason why the
AWT is still a crucial part of java.
 Swing also uses the same event handling mechanism as the AWT.
 Therefore, a basic understanding of the AWT and of event handling is required
to use swing.

3) TWO KEY FEATURES OF SWING
 Swing was created to address the limitations present in the AWT.
 It does this through two key features
 Lightweight components
 Pluggable look and feel.
1) Swing components are LightWeight
 Swing components are lightweight, means that they are written entirely in java and do
not map directly to platform-specific peers.
 Because light weight components do not translate into native peers, the look and feel
of each component is determined by swing, not by underlying operating system.
 i.e Each component will work in a consistent manner across all platforms.

2) Swing supports a pluggable look and feel
 Swing supports a pluggable look and feel(PLAF).
 Since swing follows MVC architecture, it is possible to separate the look and feel of
the component from the logic of the component.
 Separating out the look and feel provides a significant advantage
 It becomes possible to change the way that a component is rendered without affecting
any of its other aspects.
 In other words, it is possible to “plug in” a new look and feel for any given component
without creating any side effects in the code that uses that component.

 Instead, swing is built on the foundation of AWT. This is the reason why the AWT is
still a crucial part of java.
 Swing also uses the same event handling mechanism as the AWT.
 Therefore, a basic understanding of the AWT and of event handling is required to use
swing.

4) Components and containers
 Swing GUI consists of two key items
1) Components
2) Containers
 However, this distinction is mostly conceptual because all containers are also
Components
 A Component is an independent visual control, such as a push button or radio
button. A Container holds a group of components.
 Thus, a container is a special type of component that is designed to hold other
components. Furthermore, in order for a component to be displayed, it must be
held within a container.
 Thus, all Swing GUIs will have at least one container.
 Because containers are components, a container can also hold other containers.

1) Components
 In general, Swing components are derived from JComponent class.
 JComponent provides the functionality that is common to all components.
 All of Swing’s components are represented by classes defined within the package
javax.swing. Notice that all component classes begin with the letter J.

2) Containers
Swing defines two types of Containers.
2.1) Top-level containers (or) Heavy Weight Containers
2.2) Non Top-level Containers (or) Light Weight Containers

1) Top-level containers (or) Heavy Weight Containers
 The First type of containers supported by Swing are heavy Weight containers
(or) Top-level containers. They are JFrame, JApplet, JDialog, JWindow.
 These containers do not inherit JComponent. They do, however, inherit the
AWT classes Component and Container. So, we call them as Heavy Weight
Containers.
 Top-level containers are defined as those which can be displayed directly on
the desktop.
 The one most commonly used for applications is JFrame. The one used for
Applets is JApplet.

2) Non Top-level Containers (or) LightWeight Containers
 The second type of Containers supported by Swing are Light Weight Containers
(or) Non top-level Containers.
 JPanel comes under Light Weight Containers because it inherits from
JComponent.
 Light Weight Components are often used to organize and manage groups of
related controls that are contained within an outer container.

1) Top-level Container Panes
 Each top-level container defines a set of window Panes.
 A Window Pane represents a free area of a window where some text or
component can be displayed.
 We have 4 types of window panes available in javax.Swing package.
 These panes can be imagined like transparent sheets lying one below the
other.
 The Four Panes are
1) JGlassPane
2) JRoot Pane
3) JLayeredPane
4) JContentPane

JContentPane: This is the bottom most pane of all. The pane with which you will
add visual components. In other words, when you add a component, such as a
button, to a top-level container, you will add it to the content pane.
To reach this ContentPane, we use getContentPane() method of JFrame class
which returns container class object
ASIMP

import java.awt.*;
import javax.swing.*;
class Demo2 extends JFrame
{
JLabel i1,i2;
JTextField t1,t2;
Container con;
ButtonGroup rbg;
Demo2()
{
setSize(400,400);
con=getContentPane();
con.setLayout(new FlowLayout(FlowLayout.LEFT));
i1=new JLabel("Name");
t1=new JTextField(10);
i2=new JLabel("DOB");
t2=new JTextField(10);
rbg=new ButtonGroup();
JRadioButton rb1=new JRadioButton("male");
JRadioButton rb2=new JRadioButton("female");
con.add(i1);
con.add(t1);
con.add(i2);
con.add(t2);
rbg.add(rb1);
rbg.add(rb2);
con.add(rb1);
con.add(rb2);
JButton b1=new JButton("Save");
con.add(b1);}}

class Demo3
{
public static void main(String args[])
{
Demo2 ob=new Demo2();
ob.setTitle("trail box");
ob.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); ob.setVisible(true);
}
}

6) EVENT HANDLING
import java.applet.*;
/*
<applet code=Demo1 width=200 height=200>
</applet> */
public class Demo1 extends JApplet implements ActionListener
{
JButton b1,b2;
public void init()
{
b1 = new JButton("Alpha");
b2 = new JButton("Beta");
b1.addActionListener(this);
b2.addActionListener(this);
add(b1);
add(b2);
}
public void actionPerformed(ActionEvent ae)
{
if (ae.getSource() == b1)
showStatus("Alpha is pressed");
else
showStatus("Beta is pressed"); }
}
}

7) CREATE A SWING APPLET
import java.awt.*;
import java.applet.*;
/*
<applet code=AppletDemo width=300 height=300>
</applet> */
public class AppletDemo extends JApplet
{
public void paint(Graphics g)
{
g.drawString("Hello , This is a Simple Applet Program", 20,20);
}
}

8) Exploring Swing
1) JLabel and ImageIcon
2) JTextField
3) The swing Buttons
a) Jbutton
b) JRadioButton
c) JToggleButton
d) JCheckBox
4) JTabbedPane
5) JScrollPane
6) JList
7) JComboBox
8) JTrees

Exploring Swing
1) JLabel and ImageIcon
 JLabel is Swing’s easiest-to-use component.
 It is a passive component In that it does not respond to user input.
 The text can be changed by the application and not by the user. A JLabel can be
used to display text and/or an icon.
 The JLabel has the following int type constants that indicate the alignment of the
labels content.
JLabel.CENTER,JLabel.LEFT, JLabel.RIGHT,JLabel.TOP,JLabel.BOTTOM
 JLabel defines several constructors. Here are 3 of them
JLabel(Icon i)// Creates a label using the Icon i
JLabel(String str)//Creates a Label with the specified String str.
JLabel(String str, Icon i, int align)// Creates a Label using the icon I,
String Str and with the specified Alignment.

Exploring Swing
JLabel class has number of methods. Some of them are
Icon getIcon()//Returns the icon of the Label
String getText()//Returns the text of the Label
void setFont(Font font)//Sets the font for the Label’s text
void setText(String str)//Sets the specified String str as the Label’s content.

Exploring Swing
import java.awt.*; import javax.swing.*;
class lbl extends JFrame
{
JLabel I1,I2,I3;
Container con;
Icon Img1,Img2,Img3;
lbl()
{ setSize(400,400); con=getContentPane();
Img1=new ImageIcon("lion.jpg");
Img2=new ImageIcon("giraffee.jpg");
Img3=new ImageIcon("PBear.jpg");
I1=new JLabel("LION",Img1,JLabel.LEFT);
I2=new JLabel("GIRAFFE",Img2,JLabel.LEFT);
I3=new JLabel("POLAR BEAR",Img3,JLabel.LEFT);
con.add(I1); con.add(I2);con.add(I3);
}
}
class JLabelDemo
{
{
lbl ob=new lbl();
ob.setTitle("JLabel in JFrame");
ob.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); ob.setVisible(true); }
}
}

Exploring Swing
JTextField
 The JTextField class implements a single-line text-entry area, usually called an edit
control.
 TextField allow the user to enter Strings.
 JTextField is a subclass of JTextComponent, which is a subclass of JComponent/
 The Alignment of the text is defined by the following int type constants.
TextField.LEFT, JTextField.CENTER, JTextField.RIGHT
 JTextField defines the following constructors.
JTextField() // Creates a new Text field; the text is set to null and the number
of columns Is set to 0.
JTextField(int columns) //Creates a new empty textfirld with the specified
number of columns.
JTextField(String str) // Creates a new Text field with the specified string as
text.
 JTextField class has number of methods. Some of them are
String getText() // Returns the text contained in this Text Field.
String getSelectedText() // Returns the selected text contained in this text field.
Void setEditable(Boolean edit) // Sets the textfield to editable(true) or not

Exploring Swing
Import java.awt.*;
Import javax.swing.*;
Class Txt extends Jframe
{
JLabel I1,I2,I3;
JTextField t1,t2,t3;
Container con;
Txt()
{
setSize(350,200);
con=getContentPane();
I1=new JLabel(“Name”); t1=new JTextField(10);
I2=new JLabel(“RollNo”); t2=new JTextField(10);
I3=new JLabel(“Branch”); t3=new JTextField(10);
con.add(I1); con.add(t1); con.add(I2); con.add(t2); con.add(I3);
con.add(t3);
}
}
class JTextFieldDemo
{
{
Txt ob=new Txt(); ob.setTitle(“JTextField in JFrame”);
}

Exploring Swing
c) The swing Buttons Jbutton
• The JButton is a concrete subclass
of AbstractButton which is a
subclass of JComponent. The
counterpart of JButton in AWT is
Button. Perphaps the most widely
used control is the push button.
• A Push button is a component
that contains a label and that
generates an event when it is
pressed.
• JButton defines four constructors
JButton() constructs a button with no label.
JButton(String Str) constructs a button with a specified label.
JButton(Icon i) constructs a button with the icon I as button
JButton(String str, icon i) constructs a button with the icon I as button and the
string as Label
• JButton has several methods. Some of them are
void setText(String str) sets the buttons label to the specified string
void getText() Returns the label of the
button Icon getIcon() Returns the icon of the
button
void setToolTipText(String str) Sets the Tool Tip text to
the
void setMinemonic(char c) sets Shortcut key to the utton

Exploring Swing
import java.awt.*;
class Btn extends JFrame
{
JButton b1,b2,b3,b4,b5;
Btn()
{
setSize(400,350);
Container con=getContentPane();
Icon Img1=new ImageIcon(“new.jpg”);
Icon Img2=new ImageIcon(“save.jpg”);
Icon img3=new ImageIcon(“open.jpg”);
Icon img4=new ImageIcon(“back.jpg”);
Icon Img5=new ImageIcon(“forward.jpg”);
b1=new JButton(“New”,Img1);
b2=new JButton(“Save”,Img2);
b3=new JButton(“open”,Img3);
b4=new JButton(“Back”,Img4);
b5=new JButton(“Forward”,Img5);
b1.setToolTipText(“New”);
b2.setForeground(Color.red);
b3.setMnemonic(‘c’); // Shortcut key for save Button(ALT+C)
con.add(b1);
con.add(b2);
con.add(b3);
con.add(b4);
con.add(b5);
}
}

Exploring Swing
Class JButtonDemo
{
{
Btn ob=new Btn();
ob.setTitle(“JButton in JFrame”);
ob.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
ob.setVisible(true);
}
}
OUTPUT:

Exploring Swing
JRadioButton
 Radio buttons are like check boxes.
 In Radio button, the selection is displayed in a round graphics.
 Radio buttons are generally used to represent a collection of mutually exclusive options i.e,
out of several options,only one will be selected state and all the remaining are in deselected
state.
 The radio buttons are created using JRadioButton class, which is subclass of JToggleButton.
 The JRadioButton must be placed in a Button Group.
 The Button group is created using the ButtonGroup class which has no argument
constructor.
 After creating JRadioButton, the radio buttons are to be placed to the ButtonGroup using
add() method.
 If the JRadio buttons are not grouped using Buttongroup, then each radio button will behave
exactly like JCheckBox.
 JRadioButton generates ActionEvent, ItemEvent and ChangeEvent

Exploring Swing
JRadioButton defines several constructors
1) JRadioButton() // Creates a radio button without any label; the Radio Buton is set to
deselected state
2) JRadioButton(String str)//Creates a radio button with the string str as label; the ardio button
is set to deselected state
3) JRadioButton(String str, Boolean state)//Creates a radio button with the string str as label;
the radio button is set to the specified state
4) JRadioButton(Icon i)// Creates a radio button using the icon I; the radio button is set to
deselected state JRadioButton(Icon I, Boolean state)//Creates a radio button using the icon
i;the radio button is set to deselected state.
5) JRadioButton(String str,Icon i)// Creates a radio button using the icon I with the string str as
label
6) JRadioButton(String str, Icon I, Boolean state)//Creates a radio button using the Icon I with
the string str set as label; the radio button is set to the specified state

Exploring Swing
class RButton extends JFrame
{
JRadioButton rb1,rb2,rb3,rb4,mb,fb;
ButtonGroup rbg;
JLabel l1,l2;
RButton()
{ setSize(600,300);
Container c = getContentPane();
c.setLayout(new FlowLayout());
l1 = new JLabel("Buttons to be added");
l2 = new JLabel("Buttons Not added to group");
mb = new JRadioButton("Male");
fb = new JRadioButton("Female");
rb1= new JRadioButton("Times New Roman");
rb2 = new JRadioButton("Courier");
rb3 = new JRadioButton("Terminal");
rb4 = new JRadioButton("Arial");
rbg = new ButtonGroup(); c.add(l1);
c.add(rb1);
c.add(rb2);
c.add(rb3);
c.add(rb4);
rbg.add(rb1);
rbg.add(rb2);
rbg.add(rb3);
rbg.add(rb4);
c.add(l2);
c.add(mb);
c.add(fb);
}
}

Exploring Swing
class JRadioButtonDemo
{
{
RButton ob = new RButton(); ob.setTitle("JRadioButton in Jframe");
}
}

Exploring Swing
JCheckBox
The JCheckBox class provides the functionality of a check box. Its immediate superclass is
JToggleButton, which provides support for two-state buttons.
JCheckBox defines the following constructors
JCheckBox() //Creates an initially unselected check box button with no text, no icon.
JCheckBox(Icon icon)//Creates an initially unselected check box with an icon.
JCheckBox(String text)//Creates an initially unselected check box with text.
JCheckBox(Icon icon, boolean selected)//Creates a check box with an icon and specifies
whether or not it is initially selected.

Exploring Swing
class Check extends JFrame
{
JCheckBox r,s,m;
JLabel l1,l2;
Check()
{ setSize(600,300);
Container c = getContentPane();
l1 = new JLabel("Hobbies");
r = new JCheckBox("Reading");
s = new JCheckBox("Singing");
m = new JCheckBox("Listening Music");
c.add(l1);
c.add(r);
c.add(s);
c.add(m);
}
}
class JCheckBoxDemo
{
{
Check ob = new Check(); ob.setTitle("JCheckBox in Jframe");
}
}

Exploring Swing
JComoBox
• The user can select a single item only. A combo box is a visual Swing graphical
component that gives popup list when clicked.
• It is the combination of JList and JTextField.
• In Combo box, only one item is visible at a time. A Popup menu displays the choices a
user can select from.
• In JList, the items cannot be edited, but in combo box, the items can be edited by setting
the JComboBox editable.
• JCombobox defines the following constructors
JComboBox() Creates empty Combo Box
JComboBox(object[] arr) Creates a combo box taking the items from
the specified Object Array
String
1st
=(“India”,”America”,”germany”); Eg:
JComboBoxbox=newJComboBox(1st
);
JComboBox(Vector v) Creates a combo box taking the items from the
specified vector

Exploring Swing
JComboBox has so many methods. Some of them are
Void addItem(Object obj) adds the specified object to the list
Eg:box.addItem(“Japan”);
Object getSelectItem() Returns the currently selected item
Eg: Object obj=box.getSelectedItem();
Int getSelectIndex() Returns the index of item in the list
Eg: int I=box.getSelectedIndex();
Int getItemCount() Returns the number of items in the list
Eg: int I=box.getItemCount();
Boolean isEditable() Returns a Boolean specifying whether the combobox items are
Editable or not
Eg: Boolean x=box.isEditable();
Void removeItem(Object ob) Removes the specified item from the list
Eg: box.removeItem(“germany”);

Exploring Swing
import java.awt.*;
class cmbbox extends JFrame
{
JComboBox box1,box2;
String str[]={"Andhra Pradesh","Tamil Nadu","Karnataka"};
cmbbox()
{
Container c=getContentPane();
box1=new JComboBox();
box2=new JComboBox(str);
JLabel I1=new JLabel("Countries");
JLabel I2=new JLabel("States");
box1.addItem("India");
box1.addItem("germany");
box1.addItem("Japan");
c.add(I1);
c.add(box1);
c.add(I2);
c.add(box2);
}
}
class JComboDemo
{
{
cmbbox ob=new cmbbox(); ob.setTitle("JComboBox in JFrame"); ob.setSize(400,300);
}
}

JAVA UNIT 5.pptx jejsjdkkdkdkjjndjfjfkfjfnfn

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