Dr. Rajeshree Khande :Introduction to Java AWT

AWT :Abstract Window ToolKit
 AWT is collection of classes and methods that allows
to create & manage window.
 AWT provide support for Applet.
 AWT contains support for windows_ based Graphical Interface.
 To use the AWT classes & method we have to import
awt package as
import java.awt.*;
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AWT:classes
 Different window classes are defined by AWT which add
functionality with each level.
Component
Container
Window Panel
Frame Applet
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AWT:classes
 Component :
 It’ an abstract class.
 All GUI component that interact with user are
subclasses of component class.
 Defines various methods for managing event such
as keyboard & mouse input.
 Also defines attribute to store current foreground
& background colors and fonts
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AWT:classes
 Container:
 Inherits various methods & attribute of component
class
 Having additional methods of nesting other
component object.
 A container position various GUI component
within it with the help of different Layout manager
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AWT:classes
 Panel :
 It is a window which does not contain title bar,
menu bar, border.
 It is super class of Applet class.
 Any screen output written on applet is drawn on
the surface of panel object.
 AppletViewer provide titlebar & border to an
applet.
 We add GUI component such as buttons ,list box
to a panel.
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AWT:classes
 Window :
 Window class is used to create top level window.
 Window object are not created directly.
 Subclass of window is used to place on desktop.
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AWT:classes
 Frame:
 It is subclass of window.
 It has title bar , menu bar & border etc
 To create a normal window in Java application Frame class
is used.
 In Applet we does not use Frame class, since AppletViewer
provide titlebar, menubar & boarder to an applet.
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AWT:classes
 Canvas:
 It is not subclass of window or panel.
 It is another type of window.
 This widow is blank window upon which we can
draw.
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Layout Managers
 It is an object which determine the way that
component are arranged in frame window.
 It arranges a control within a window using some
type of an algorithm.
 Each window has a layout manager associated with
it.
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Layout Managers
 LayoutManager is set by the setLayout() method
to a window.
syntax
void setLayout(LayoutManager layobj)
 If it is not set then default layout manager is used
 If layobj parameter set to null then control are
positioned manually using the setBound() method
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LayoutManager Classes
1.FlowLayout
 Default frame layout.
 Places Components in successive rows in window fitting as
many as in each row as possible.
 When the row is full it start fitting the components on the
next row.
 This is similar to how word flow in text editor
 A small space is left in each component.
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LayoutManager Classes :FlowLayout
 Following are constructor for FlowLayout.
1. FlowLayout()
Centers all component and leves 5 pixel space between each component
2. FlowLayout(int align)
Flowlayout.LEFT
Flowlayout.CENTER
Flowlayout.RIGHT
Flowlayout.LEADING
Flowlayout.TRAILING
3. FlowLayout(int align, int hspace, int vspace)
 Example
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LayoutManager Classes :BorderLayout
 Frame is divided into north, south, east, west, and
center
 Components are placed by the programmer in the
desired location using the add method
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Following are constructor for BorderLayout
1) BorderLayout()
2) BorderLayout(int hspace, int vspace)
To add a component in BorderLayout use following
format of add() method
Syntax :
void add(Component-obj, Object Region)
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 Where region specifies following five
constant:
1. BorderLayout.EAST
2. BorderLayout.WEST
3. BorderLayout.SOUTH
4. BorderLayout.NORTH
5. BorderLayout.CENTER
Example
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:GridLayout
2.GridLayout
 Frame is declared as a grid of fixed size
(e.g. two rows and three columns)
 Components are placed in the grid left to
right and top to bottom
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:GridLayout
 GridLayout uses following Constructor
1) GridLayout()
Creates a single column grid Layout
2) GridLayout(int nrows, int ncols)
Creates a grid layout with specified no. of rows and
columns
3) GridLayout(int nrows, int ncols, int hspcae, int vspace)
Creates a grid layout with specified no. of rows and
columns and specifies horizontal and vertical space
between the component
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:GridLayout
 Example1
 Example1
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AWT Component
Adding a control
1. Create an instance of desired control
2. Then add it to window by calling add() method which is define by
container
3. The add method has several form
4. Once the control has been added it will be automatically visible
whenever it’s parent window is display
Syntax
Component add(Component compObj)
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AWT Component
Removing a control
 If control no longer need we will remove that control
by remove() method
 This method also defined by Container class
Syntax
void remove (Component compObj)
 We can remove all controls by removeAll() method
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AWT Component
Responding to controls
1. All control except label generates events when they
are accessed by user.
2. In general , your program simply implements the
appropriate interface & register an event listener
for each control that need to monitor.
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AWT Component
Label
1. It is an object type Label
2. It is a passive control
3. Do not support any interaction
Following Constructor
1. Label() : Construct blank label
2. Label(String) : construct a label containing string
3. Label(String, int) :
Alignment
( Label.LEFT,Label.RIGHT,
Label.CENTER) 24RAJESHREE KHANDE

AWT Component :Label
 Methods
Sr.
No
Methods Description
1 void setText(String) Set or change a text of label
2 String getText() Obtain the text of label
3 void setAlignment(int) Set or change the alignment
of text in the label
4 int getAlignment() Obtain the current alignment
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AWT Component :Push Button
1. It is push button component
2. Contain a label
3. Generate a event when it is pressed
4. It is an object of type Button
5. Button defines two constructor
1. Button() : Create a buttton without label
2. Button (String str) :Creates a button with label
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 Methods
Sr.
No
Methods Description
1 void setLabel(String) Set or change a label of
Button
2 String getLabel() Obtain the label Button
AWT Component :Push Button
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AWT Component :TextField
 TextField class is used to create a single line text
entry edit box.
 Constructor
1. TextField() : Creates a default textfield
2. TextField(int) : Creates a textfield which wide as
specified number of characters.
3. Textfield(String) : Creates a textfield with specified
string initially.
4. TextField(String, int) : Creates a textfield with initial
text and set it’s width.
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 Methods
Sr.
No
Methods Description
1 String getText() Return the content of TextField.
2 void setText(String) Set or change the text of TextField.
3 String getSelectedText() To get currently selected text
4 void select(int startIndex, int
endIndex)
To select portion of text
5 boolean isEditable() To determine editability
6 void setEditable(boolean) To set or reset editability 29RAJESHREE KHANDE

 Example1 :Button and Label
 Example2 : Conversion to binary ,Hexadecimal, Octal
 Example 3: Converting String to Uppercase and
Lowercase
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AWT Component :Check Box
 Used to toggle an option
 A Checkbox class is used to create an object
 Constructor
1. Checkbox() :
Creates a checkbox without label.
2. Checkbox(String) :
Creates a checkbox with label specified initial state is
unchecked.
3 Checkbox(String, boolean) :
Creates a checkbox with label specified initial state is
either true or false.
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AWT Component :Check Box
 Methods
Sr.
No
Methods Description
1 Boolean getState() Retrieve the current state
2 void setState(boolean) Set the state true or false
3 String getLabel() Retrieve the label associated
4 Void setLabel(String) Sets the label as specified
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AWT Component :CheckBoxGroup
 It is also called radio buttons
 CheckBoxGroup class is used to create group of
check boxes.
 From list of choices we select only one at a time.
 Constructor
CheckboxGroup()
e.g.
CheckBoxGroup cbg = new CheckBoxGroup()
c1 = new Checkbox("check-1“,cbg,true);
c2 = new Checkbox("check-2“,cbg,false);
c3 = new Checkbox("check-3“,cbg,false);
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AWT Component :CheckBoxGroup
Method :
1)getSelectedCheckbox() : determine which
checkbox in a group is currently selected
Checkbox getSelectedCheckbox()
2)setSelectedCheckbox() : set a check box
void setSelectedCheckbox(Checkbox obj))
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AWT Component :List
 Provide a list of items, which can be scrolled
 From list of items single or multiple item can be
selected.
 Constructor
1. List() : Creates a listbox in which single selection is
possible.
2. List(int) :Creates a listbox , specified number of
items always to visible selection.
Selection is possible
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AWT Component :List
3. List(int, boolean) :
Specified no. of items
To be visible
Specifies wheather
multiple selection is
allowed
True Indicate multiple
Selection
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AWT Component :List
Sr.
No
Methods Description
1 Void add(string) Add item to the end of list
2 Void add(String,int) Add the item at the index specified
in second parameter.
3 String getSelectedItem() Returns a string which is selected
4 int getSelectedIndex() Return an index of selected item
5 String[] getSelectedItems() Returns an array contains string
which are selected.(Multiselect)
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AWT Component :List
Sr.
No
Methods Description
6 Int[] getSelectedIndexes() Returns an array containing
indexes of selected items.
7 Int getItemCount() Returns no. of items in the list
8 Void select(int) Select the item of specified index
9 String getItem(int) Obtain the name of item having
specified index.
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AWT Component :List
 Example1
 Example2
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AWT Component :Choice list
 The class Choice is used to create a drop-down or
pop-up list of string
 It requires less space than the list box control
 It uses only default constructor
Choice()
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Sr.
No
Methods Description
1 void add(String) To add a string in choice list
2 String getSelectedItem() Determine which item is currently selected
3 int getSelectedIndex() Determine the index of currently selected
item.
4 int getItemCount() Returns no. of items in the list
5 void select(int) Select the item whose index is specified
6 void select(String) Select the item match with string parameter
7 String getItem(int) Obtain the name associated with the item at
specified index
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 Example of Choice list
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AWT Component :TextArea
 TextArea class is used to create a multiline textbox
Following constructor are available
1. TextArea() :
Creates a default TextArea
2. TextArea(int, int) :
Creates a TextArea with specified no. of lines &
characters.
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3. TextArea(String) :
Create with initial string.
4. TextArea(Sring, int, int) :
Creates a TextArea with initial string and for
specified no. of lines & characters.
5. TextArea(String, int numlines, int nchar, int s bars)
Creates a TextArea with Scroll Bars. The value of
sBars must be one of the following
SCROLLBAR_BOTH, SCROLLBAR_NONE,
SCROLLBAR_HORIZONTAL_ONLY,
SCROLLBAR_VERTICAL_ONLY
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 Support all the methods of TextField & some
additional method
Sr.
No
Methods Description
1 void append(String) Append Specified string at the
end.
2 void insert(string,int) Insert a string at specified index
3 void replace(String, int
startIndex, endIndex)
It replaces the character from
start index to end with given
string
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AWT Component :Scroll Bars
 Scrollbar class is used to create scrollbar.
 Scrollbar may be either vertical or horizontal.
 Constructor
1. Scrollbar() :
Create vertical scrollbar.
2. Scrollbar(int style) :
Create a scrollbar of specified style. It can be
Scrollbar.HORIZONTAL
Scrollbar.VERTICAL
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AWT Component :Scrollbar
3. Scrollbar(int style, int start, int thumb,int min, int max) :
Create a scrollbar with specified style.
Initial Value Thumbsize
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AWT Component :Scrollbar
Sr.
No
Methods Description
1 int getValue() To get the current value of scroll bar
2 void setValue(int) Set new value
3 int getMinimum() To get minimum value of scrollbar
4 int getMaximum() To get maximum value of scrollbar
5 void setUnitIncrement(int) To change unit increment.
Default is 1
6 void setBlockIncrement(int) To change block increment.
Default is 10
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Graphics
 AWT support a rich assortment of Graphics methods.
 All graphics are drawn relative to window.
 This can be main window of an applet, Child window
of an applet or stand alone application window
 The origin of window is at the Top-left corner and is
(0,0).
 Co-ordinates is specified in pixel.
 All output to a window takes place through a
graphics context.
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Graphics
 Graphics Context is encapsulated by Graphics class &
is obtained in two ways.
1. It is passed to an applet when one of it’s various
methods, such as paint() or update() .
2. It is returned by getGraphics() method of Component
 The Graphics class defines the a number of
drawing functions
 Each shape can be drawn edge-only or filled
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Graphics
 Object are drawn and filled in currently selected
graphics color, which is black by default.
 When a graphics object is drawn that exceeds the
dimension of the window, output is automatically
clipped
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Drawing Lines
 Lines are drawn by means of the drawLine() method
void drawLine(int startX, int startY,int endX, endY)
drawLine() display a line in the current drawing
color.
Example
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Drawing Rectangle
 drawRect() method display an outline of rectangle
 fillRect() method filled the rectangle.
void drawRect(int top,int left,int width, int height)
void fillRect(int top, int left, int width, int height)
 The upper-left corner of the rectangle is top,left
 The dimension of the rectangle are specified by
width and height.
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Drawing Rounded Rectangle
 To draw Rounded Rectangle use drawRoundRect() of
fillRoundRect().
void drawRect(int top,int left,int width, int height)
void fillRect(int top, int left, int width, int height)
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:CardLayout
 CardLayout
-- Display containers you pass to it as card.
-- You give each card a name.
-- The card are typically held in an object of type Panel
-- We can move from card to card with the Card’s
layout show() method.
--We can also display specific cards using first , last, next & previous
method of CardLayout.
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 is encapsulated by graphics class & is obtained in two
ways.
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:CardLayout
 Constructor
1) CardLayout() :
creates new card layout
2) CardLayout(int hspace,int vspace)
creates new card layout with given horizontal and
vertical space
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:CardLayout
Step for CardLayout
1. Create a panel that contains a deck and panel for each card
in the deck.
2. Add to the appropriate panel the components that form
each card.
3. Then add these panels to the panel for which CardLayout is
the layout manager
4. Finally you add this panel to window
5. To select between the cards ,include one push button for
each card in the deck.
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:CardLayout
 When panels are added to panel, they are given a name.
So use the following add method
Void add(Component panelObj, Object name)
Name of the card whose
panel is specified by
panelObj
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:CardLayout
 After deck creation, you can activate a card by
calling one of the method defined by CardLayout
1. void first(Container deck)
2. void last(Container deck)
3. void next(Container deck)
4. void previous(Container deck)
5. void show(Container deck,String cardName) 60RAJESHREE KHANDE

:CardLayout
 deck : is the reference to the container(usually panel)
that holds the card
 cardName : is the name of the card
 Example
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Scrollbars
 The leftmost position of a horizontal scrollbar
corresponds to some integer value and the rightmost
position corresponds to a larger integer value
 Scrollbars can be displayed vertically
 User movement options
 Clicking either end button causes bubble to move in
unit increments.
 Clicking the are between bubble and end button
causes movement in 10 unit increments
 Clicking and dragging the bubble in the desired
direction
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Using Inheritance
 It is possible to use inheritance to allow
TwoButtons to become a frame in its own
right
 Note that the UML diagram will show
TwoButtons as a subclass of Frame
 You will need to use super()to set the
frame title
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Dr. Rajeshree Khande :Introduction to Java AWT

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Dr. Rajeshree Khande :Introduction to Java AWT