ABSTRACT WINDOW TOOLKIT
AWT contains various classes and methods that
allow you to create and manage windows.
The AWT contains the foundation for Swing
AWT Classes:
Button Create a push button
control
Checkbox Creates a check box
control
CheckboxGroup Creates a group of
checkboxes
Choice Creates a pop-up list
Color Manages colors in a
portable platform-
independentfashion
Component An abstract superclass for
various AWT
components
Container A subclass of Component
that can hold other
components
Dialog Creates a dialog window
Font Encapsulates a type font
Frame Creates a standard
window that has a title
bar, resize corners and a
menu bar.
Graphics Encapsulates the graphics
context
GridLayout The grid layout
manager,displays
components in a two
dimensional grid
Label Creates a label that
displays a string
List Creates a list from which
the user can choose
Menu Creates a pulldown menu
MenuBar Creates a menubar
Panel Simplest concrete
subclass of Container
Scrollbar Creates a scrollbar
control
TextArea Creates a multiline edit
control
TextComponent A super class of
TextArea and TextField
TextField Creates a single line edit
control
Window Creates a window with
no frame,no menu bar ,
and no title
CLASS HIERARCHY:
Component
Container
Window Panel
Frame
Component
top of the AWT hierarchy
is an abstract class that encapsulates all of the
attributes of a visual component
all the user interface elements that are
displayed on the screen and that interact with
the user are subclasses of Component
defines hundreds of public methods
responsible for managing events
Container
Subclass of Component
Has additional methods that allow other
Component objects to be nested within it
Responsible for laying out i.e positioning
of components
Panel
Concrete subclass of Container
Superclass of Applet
Is a window that doesnot contain a title
bar menu bar or border
That’s why we don’t see them when
applet is run from a browser
Window
The window class creates a top-level window
which is not contained within any other
object ; it sits on the desktop
So we don’t create Window object directly
and use a subclass of Window called Frame
Frame
Encapsulates what is commonly thought
as a window
Subclass of Window and has a title bar,
menu bar, borders, and resizing corners
Working with Graphics
Graphics class defines a number of drawing functions
Drawing Lines:
void drawLine(int startX,int startY,int endX,int endY)
Drawing Rectngles
void drawRect(int top,int left,int widthe,int height)
void fillRect(int top,int left,int widthe,int height)
void drawRoundRect(int top,int left,int widthe,int
height,int xDiam,int yDiam)
void fillRoundRect(int top,int left,int widthe,int
height,int xDiam,int yDiam)
Drawing Ovals
void drawOval(int top,int left,int widthe,int height)
void fillOval(int top,int left,int widthe,int height)
Drawing Arcs
void drawArc(int top,int left,int widthe,int height,int
startangle,int sweetangle)
void fillArc(int top,int left,int widthe,int height,int
startangle,int sweetangle)
Drawing Polygons
void drawPolygon(int x[],int y[],int nmpts)
void fillPolygon(int x[],int y[],int nmpts)
Setting colors can be done as g.setColor(Color.red)
If u wish to see the overridden images then use
g.setXORMode(Color.black)
EXAMPLE PROGRAM
import java.awt.*;
import java.applet.*;
/*<applet code="Applet2" width=500 height=600>
</applet>
*/
public class Applet2 extends Applet
{
public void paint(Graphics g)
{
g.drawLine(20,30,100,200);
g.drawRect(10,10,60,50);
g.fillRect(400,100,60,50);
g.drawRoundRect(190,10,60,50,15,15);
g.fillRoundRect(700,900,140,100,30,40);
g.drawOval(150,150,50,50);
g.fillOval(200,200,75,50);
g.drawArc(150,40,70,70,0,75);
g.setColor(Color.blue);
g.fillArc(100,40,70,70,0,75);
g.setColor(Color.red);
int xpo[]={30,200,30,200,30};
int ypo[]={30,30,200,200,30};
int num=5;
g.drawPolygon(xpo,ypo,num);
g.setColor(Color.cyan);
int xpo1[]={300,200,300,200,300};
int ypo1[]={300,300,200,200,300};
int num1=5;
g.setXORMode(Color.white);
g.fillPolygon(xpo1,ypo1,num1);
}
}
AWT Controls and Layout Managers:
Controls are components that allow a user to interact
with your application in various ways for ex: control
like a push button,labels,checkbox etc
Layout manager automatically positions components
within a container… if not specified the default
layout manger will be used
Control Fundamentals
To include a control in a window you must add it
to the window by creating an instance of the
desired control and then adding it to a window by
calling add() defined by Container.
Forms of add()
Component add(Component cobj)
To remove a control from a window call
remove() defined in Container
Void remove(Component cobj)
You can remove all the controls by calling
removeAll()
Except for labels , which are passive , all
controls generate events when they are accessed
by the user.
Most of AWT controls throw a
HeadlessException when an attempt is made to
instantiate a GUI component in a non-
interactive environment such as no
display,mouse,or keyboard)
LABELS
A label is object of type Label and contains a
string which it displays
Constructors are
Label() throws HeadlessException
Label(String str) throws HeadlessException
Label(String str,int how) throws
HeadlessException
First version creates empty label
Second creates a label that contains the string
specified and is left-justified
The third creates a label that contains the string
specified and the alignment specified by ‘how’.
You can set or change the tex in a label by using
setText() and can obtain the current label by
getText() method.
Void setText(String str)
String getText()
You can set alignment using setAlignment() and
obtain the current by getAlignment()
void setAlignment(int how)
int getAlignment()
PROGRAM
import java.awt.*;
import java.applet.*;
/*<applet code="LabelDemo" width=500
height=600>
</applet>
*/
public class LabelDemo extends Applet
{
public void init()
{
Label one=new Label("ONE");
Label two=new Label("TWO");
Label three=new Label("THREE");
add(one);
add(two);
add(three);
}}
BUTTONS
a push button is a component that contains a
label and that generates an event when it is
pressed, are objects of type Button.
2 contructors
Button() throws HeadlessException
---Creates an empty button and label can be set
using setLabel()
---void setLabel(String str)
Button(String str) throws HeadlessException
--creates a button that contains str as a label
---can retrieve its label by getLabel()
--String getLabel()
Each time a button is pressed, an action event is
generated that is sent to any listeners registered;
each listener implements ActionListener interface
that defines actionPerformed() method which is
called whenever an event occurs.
The label can be obtained by calling
getActionCommand() on ActionEvent object
passed to actionPerformed().
PROGRAM
import java.awt.*;
import java.applet.*;
import java.awt.event.*;
/*<applet code="ButtonDemo" width=500
height=600>
</applet>
*/
public class ButtonDemo extends Applet
implements ActionListener
{
String msg="";
Button yes,no,maybe;
public void init()
{
yes=new Button("YES");
no=new Button("NO");
maybe=new Button("MAYBE");
add(yes);
add(no);
add(maybe);
yes.addActionListener(this);
no.addActionListener(this);
maybe.addActionListener(this);
}
public void actionPerformed(ActionEvent ae)
{
String str=ae.getActionCommand();
if(str.equals("YES"))
msg="U PRESSED YES";
else if(str.equals("NO"))
msg="U PRESSED NO";
msg="U PRESSED UNDECIDED";
repaint();
}
public void paint(Graphics g)
{
g.drawString(msg,30,200);
}
}
CHECKBOXES:
---A checkbox is a control that is used to turn an
option on or off.
--Constructors:
1. Checkbox() throws HeadlessException
---creates check box whose label is initially blank
and to set the label setLabel() is used
---void setLabel(String str)
2. Checkbox(String str) throws
HeadlessException
----creates checkbox with the label as str and the
state of the checkbox is unchecked
3. Checkbox(String str,Boolean on) throws
HeadlessException
----allows to set the initial state of the checkbox ;
if variable on is true , then the checkbox is
initially checked otherwise is cleared.
4. Checkbox(String str,Boolean
on,CheckboxGroup cb) throws
HeadlessException
----creates checkbox with label as str and group
specified by cb ; if not a part of this group then
cb will be null.
---to get current label
String getLabel()
----to set the state call setState()
void setState(boolean o); if o is on then checked
else cleared
---each time checkbox is selected or deselected an
itemevent is generated which is sent to the
listeners registed with it ; all these listeners shud
implement ItemListener interface which defines
itemStateChanged() method.
PROGRAM
import java.awt.*;
import java.applet.*;
import java.awt.event.*;
/*<applet code="CheckboxDemo" width=500
height=600>
</applet>
*/
public class CheckboxDemo extends Applet
implements ItemListener
{
String msg="";
Checkbox winXP,solaris,mac;
public void init()
{
winXP=new Checkbox("Windows
XP",null,true);
solaris=new Checkbox("Solaris");
mac=new Checkbox("Mac Os",true);
add(winXP);
add(solaris);
add(mac);
winXP.addItemListener(this);
solaris.addItemListener(this);
mac.addItemListener(this);
}
public void itemStateChanged(ItemEvent ae)
{
repaint();
}
public void paint(Graphics g)
{
msg="windows XP : "+winXP.getState();
g.drawString(msg,30,200);
msg="Solaris : "+solaris.getState();
g.drawString(msg,30,250);
msg="mac OS : "+mac.getState();
g.drawString(msg,30,300);
}
}
CHECKBOXGROUP
---to create a set of mutually exclusive check boxes in
which one and only one checkbox in the group can be
checked at anyone time ….these are often called “radio
button”
---we can determine which checkbox in a group is
currently selected by calling getSelectedCheckbox()
and can set a checkbox by calling
setSelectedCheckbox()
--Checkbox getSelectedCheckbox()
--void setSelectedCheckbox(Checkbox which)
PROGRAM
import java.awt.*;
import java.applet.*;
import java.awt.event.*;
/*<applet code="CBGroup" width=500 height=600>
</applet>
*/
public class CBGroup extends Applet implements
ItemListener
{
String msg="";
Checkbox winXP,solaris,mac;
CheckboxGroup cbg;
public void init()
{
cbg=new CheckboxGroup();
winXP=new Checkbox("Windows XP",cbg,true);
solaris=new Checkbox("Solaris",cbg,true);
mac=new Checkbox("Mac Os",cbg,false);
add(winXP);
add(solaris);
add(mac);
winXP.addItemListener(this);
solaris.addItemListener(this);
mac.addItemListener(this);
}
public void itemStateChanged(ItemEvent ae)
{
repaint();
}
public void paint(Graphics g)
{
msg=cbg.getSelectedCheckbox().getLabel();
g.drawString(msg,30,200);
}
}
