�ݺ�ߣ

Abstract Windowing Toolkit
AWT

Introduction
• Java AWT (Abstract Windowing Toolkit) is an API to develop
GUI or window-based application in java.
• Java AWT components are platform-dependent i.e. components
are displayed according to the view of operating system.
• AWT is heavyweight i.e. its components uses the resources of
system.
• The java.awt package provides classes for AWT API such as
TextField, Label, TextArea, RadioButton, CheckBox, Choice,
List etc.

Object
• The Object class is the top most class and parent of all
the classes in java by default.
• Every class in java is directly or indirectly derived from
the object class.

Component
• The Component is abstract class that encapsulates all
the attributes of visual component.
• All User interface (UI) elements that are displayed on
screen are subclasses of Component.
Component is responsible for remembering the current
foreground and background color and the currently
selected text font.

Methods of Component class
Method Description
public void add(Component c) inserts a component on this
component.
public void setSize(int width, int
height)
sets the size (width and height) of the
component.
public void setLayout(LayoutManager
m)
defines the layout manager for the
component.
public void setVisible(boolean status) changes the visibility of the component,
by default false.
void remove(Component c) Remove a component
void setBounds(int x,int y, int width,
int height)
Set the location and size of single
component and useful only with null
layout.

Container
• The Container is a component in AWT that can contain
another components like buttons, textfields, labels etc.
• The classes that extends Container class are known as
container such as Frame, Dialog and Panel.
• Container is responsible for laying out any
components that it contains through the use of layout
managers.
• Methods:
• void setFont(Font f)
• void setLayout(LayoutManager mgr)

Panel
• Panel class is concrete class it doesn’t add new
methods.
• The Panel is the container that doesn't contain title
bar and menu bars and Borders.
• It can have other components like button, textfield etc.

An Applet is Panel is a Container
java.lang.Object
| +----java.awt.Component
| +----java.awt.Container
| +----java.awt.Panel
| +----java.applet.Applet

An Applet
• Applet is a public class which is predefined by
java.applet.Applet
• There is no main() method in Applet like
Application program. The main() method is
defined by browser or Appletviewer for Applet.
• Life cycle methods: init, start, paint, stop, destroy
• Applet is one type of container and subclass of
Panel.

To create an applet
• import java.applet.*;
• Import java.awt.*;
• Applet tag code in comment.
• Extends Applet class
• Life cycle method
• Class must be public

Window
• The window is the container that have no borders and
menu bars.
• You must use frame, dialog or another window for
creating a window.

Frame
• It is subclass of Window.
• The Frame is the container that contain title bar and
can have menu bars,borders, and resizing corners.
• It can have other components like button, textfield, etc.
• Methods:
• void setTitle(String title)
• void setBackground(Color bgcolor)

Working with Frame Window
• Extends Frame class
• Constructor are:
• Frame()
• Frame(String title)
• Setting and Getting window size:
• void setSize(int width, int height)
• void setSize(Dimension newsize)
• Showing and Hiding Frame
• void setVisible(boolean visibleFlag)

Frame Class
• We can create stand-alone AWT based applications.
• A Frame provides main window for the GUI application.
• There are two ways to create a Frame :
1.By instantiating Frame Class
2.By extending Frame class

Label
• The easiest control to use is a label.
• A label is an object of type Label, and it contains a
string, which it displays.
• Labels are passive controls that do not support any
interaction with the user.

Labels
• Label defines the following constructors:
• Label( )
• Label(String str)
• Label(String str, int how)
• The first version creates a blank label.
• The second version creates a label that contains the
string specified by str. This string is left-justified.
• The third version creates a label that contains the string
specified by str using the alignment specified by how.
The value of how must be one of these three constants:
Label.LEFT, Label.RIGHT, or Label.CENTER.

Buttons
• 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.
• Push buttons are objects of type Button.
• Button defines these two constructors:
• Button( )
• Button(String str)

Check Boxes
• A check box is a control that is used to turn an option on
or off.
• It consists of a small box that can either contain a check
mark or not.
• There is a label associated with each check box that
describes what option the box represents.
• We change the state of a check box by clicking on it.
Check boxes can be used individually or as part of a
group.

Checkbox constructors:
• Checkbox( )
• Checkbox(String str)
• Checkbox(String str, boolean on)
• Checkbox(String str, boolean on, CheckboxGroup cbGroup)
• Checkbox(String str, CheckboxGroup cbGroup, boolean on)

Methods
• boolean getState( )
• void setState(boolean on)
• String getLabel( )
• void setLabel(String str)
• void addItemListener(ItemListener l)
• void removeItemListener(ItemListener l)

events,key,life cycle-abstract window tool kit,abstract class

Checkbox Group
• It is possible to create a set of mutually exclusive
check boxes in which one and only one check box in
the group can be checked at any one time.
• These check boxes are often called radio button.
• Check box groups are objects of type
CheckboxGroup.
• Only the default constructor is defined, which creates
an empty group.

Methods
Checkbox getSelectedCheckbox( )
void setSelectedCheckbox(Checkbox wh)

Choice Controls
• The Choice class is used to create a pop-up list of items
from which the user may choose.
• Thus, a Choice control is a form of menu.
• Each item in the list is a string that appears as a left
justified label in the order it is added to the Choice
object.

Methods
void add(String name)
String getSelectedItem( )
int getSelectedIndex( )
int getItemCount( )
void select(int index)
void select(String name)
String getItem(int index)

Lists
• The List class provides a compact, multiple-choice,
scrolling selection list.
• Unlike the Choice object, which shows only the single
selected item in the menu, a List object can be
constructed to show any number of choices in the
visible Window.
• It can also be created to allow multiple selections.

List
• List( )
• List(int numRows)
• List(int numRows, boolean multipleSelect)
• The first version creates a List control that allows only one item to be
selected at any one time.
• In the second form, the value of numRows specifies the number of
entries in the list that will always be visible (others can be scrolled into
view as needed).
• In the third form, if multipleSelect is true, then the user may select two
or more items at a time.

Methods
void add(String name)
void add(String name, int index)
String getSelectedItem( )
int getSelectedIndex( )
String[ ] getSelectedItems( )
int[ ] getSelectedIndexes( )
int getItemCount( )
void select(int index)
String getItem(int index)

ScrollBars
• Scroll bars are used to select continuous values
between a specified minimum and maximum.
• Scroll bars may be oriented horizontally or
vertically.
• A scroll bar is actually a composite of several individual
parts.
• slider box (or thumb) for the scroll bar.
• The slider box can be dragged by the user to a new
position, this action translates into some form of page
up and page down.

Constructors
• Scrollbar( )
• Scrollbar(int style)
• Scrollbar(int style, int iValue, int tSize, int min, int
max)
• The first form creates a vertical scroll bar.
• The second and third forms allow us to specify style
Scrollbar.VERTICAL, Scrollbar.HORIZONTAL.
• In the third form, the initial value of the scroll bar is passed
in iValue. The number of units represented by the height of
the thumb is passed in tSize. The minimum and maximum
values for the scroll bar are specified by min and max.

Methods
void setValues(int iValue, int tSize, int min, int max)
int getValue( )
void setValue(int newValue)
int getMinimum( )
int getMaximum( )
void setUnitIncrement(int newIncr)
void setBlockIncrement(int newIncr)

TextField
• The TextField class implements a single-line
text-entry area, called an edit control.
• Text fields allow the user to enter strings and
to edit the text using the arrow keys, cut and
paste keys, and mouse selections.
• TextField is a subclass of TextComponent.

TextField Constructors
• TextField( )
• TextField(int numChars)
• TextField(String str)
• TextField(String str, int numChars)

• String getText( )
• void setText(String str)
• String getSelectedText( )
• void select(int startIndex, int endIndex)
• boolean isEditable( )
• void setEditable(boolean canEdit)
• void setEchoChar(char ch)
• boolean echoCharIsSet( )
• char getEchoChar( )
TextField Methods

TextArea
• Sometimes a single line of text input is not enough for
a given task. To handle these situations, the AWT
includes a simple multiline editor called TextArea.
• Following are the constructors for TextArea:
• TextArea( )
• TextArea(int numLines, int numChars)
• TextArea(String str)
• TextArea(String str, int numLines, int numChars)
• TextArea(String str, int numLines, int numChars,
int sBars)
sBars must be one of these values: SCROLLBARS_BOTH,
SCROLLBARS_NONE,SCROLLBARS_HORIZONTAL_ONLY,
SCROLLBARS_VERTICAL_ONLY

Methods
• TextArea is a subclass of TextComponent.
• Therefore, it supports the getText( ), setText( ),
getSelectedText( ), select( ), isEditable( ), and
setEditable( ) methods as of TextField.
• TextArea adds the following methods:
• void append(String str)
• void insert(String str, int index)
• void replaceRange(String str, int startIndex, int
endIndex)

Layout Managers
• Layout means arranging the components within
the container.
• The task of lay outing can be done automatically by
the Layout manager.
• The layout manager is set by the setLayout( )
method.
• If no call to setLayout( ) is made, then the default
layout manager is used.
• Whenever a container is resized (or sized for the
first time), the layout manager is used to position
each of the components within it.

• The setLayout( ) method has the following
general form:
• void setLayout(LayoutManager layoutObj)
• Here, layoutObj is a reference to the desired
layout manager.
• If we wish to disable the layout manager and
position components manually, pass null for
layoutObj.

LayoutManager
• LayoutManager is an interface that is
implemented by all the classes of layout managers.
There are following classes that represents the
layout managers:
• FlowLayout
• BorderLayout
• GridLayout
• CardLayout
• GridBagLayout

FlowLayout
• FlowLayout is the default layout manager.
• FlowLayout implements a simple layout style,
which is similar to how words flow in a text
editor.
• Components are laid out from the upper-left
corner, left to right and top to bottom.
• When no more components fit on a line, the next
one appears on the next line.
• A small space is left between each component,
above and below, as well as left and right.

FlowLayout Constructors
• FlowLayout( )
• FlowLayout(int how)
• FlowLayout(int how, int horz, int vert)
• The first is default, which centers components and leaves
five pixels of space between each component.
• The second form lets us specify how each line is aligned.
Valid values for how are as follows:
• FlowLayout.LEFT
• FlowLayout.CENTER
• FlowLayout.RIGHT
• The third form allows us to specify the horizontal and
vertical space left between components

FlowLayout Methods
• int getAlignment()
• int getHgap()
• int getVgap()
• int setAlignment(int align)
• int setHgap(int hgap)
• int setVgap(int vgap)

BorderLayout
• The BorderLayout class implements a common
layout style for top-level windows.
• It has four narrow, fixed-width components at
the edges and one large area in the center.
• The four sides are referred to as
• north,
• south,
• east, and
• west.
• The middle area is called the center.

BorderLayout Constructors
• BorderLayout( )
• BorderLayout(int horz, int vert)
• The first form creates a default border layout.
• The second allows us to specify the horizontal
and vertical space left between components in
horz and vert, respectively.

BorderLayout
• BorderLayout defines the following constants that
specify the regions:
• BorderLayout.CENTER
• BorderLayout.SOUTH
• BorderLayout.EAST
• BorderLayout.WEST
• BorderLayout.NORTH
• To add components, we use these constants with the
following form of add( ), which is defined by
Container:
• void add(Component compObj, Object region);
• Here, compObj is the component to be added, and
region specifies where the component will be added.

public class BorderLayoutDemo extends Applet {
public void init() {
setLayout(new BorderLayout());
add(new Button("This is across the top."), BorderLayout.NORTH);
add(new Label("The footer message."), BorderLayout.SOUTH);
add(new Button("Right"), BorderLayout.EAST);
add(new Button("Left"), BorderLayout.WEST);
String msg = "The reasonable man adapts himself to the world;n" +
"the unreasonable one persists in trying to adapt the world to
himself.n" +
"Therefore all progress depends on the unreasonable man.nn" + " -
George Bernard Shawnn";
add(new TextArea(msg), BorderLayout.CENTER);
}
}

GridLayout
• GridLayout lays out components in a two-
dimensional grid.
• When we instantiate a GridLayout, we define the
number of rows and columns.

GridLayout constructors
• GridLayout( )
• GridLayout(int numRows, int numColumns )
• GridLayout(int numRows, int numColumns, int horz,
int vert)
• The first form creates a single-column grid layout.
• The second creates a grid layout with specified number of
rows and columns.
• Either numRows or numColumns can be zero.
• Specifying numRows as zero allows for unlimited-length
columns.
• Specifying numColumns as zero allows for unlimited-length
rows.

CardLayout
• The CardLayout class is unique among the other
layout managers in that it stores several different
layouts.
• Each layout can be thought of as being on a separate
index card in a deck that can be shuffled so that any
card is on top at a given time.
• This can be useful for user interfaces with optional
components that can be dynamically enabled and
disabled upon user input.
• We can prepare the other layouts and have them
hidden, ready to be activated when needed.

• CardLayout provides these two constructors:
• CardLayout( )
• CardLayout(int horz, int vert)
• The first form creates a default card layout.
• The second form allows us to specify the
horizontal and vertical space left between
components.

Methods
• void add(Component panelObj, Object name);
• Here name is a string that specifies the name of the card
whose panel is specified by panelObj. After we have
created a deck, our program activates a card by calling
one of the following methods:
• void first(Container deck)
• void last(Container deck)
• void next(Container deck)
• void previous(Container deck)
• void show(Container deck, String cardName)
• deck is a reference to the container (usually a panel) that
holds the cards, and cardName is the name of a card.

• // Demonstrate CardLayout.
import java.awt.*;
import java.awt.event.*;
public class CardLayoutExample extends Frame implements
ActionListener{
CardLayout card;
Button b1,b2,b3;
CardLayoutExample(){
card=new CardLayout(40,30);
setLayout(card);

b1=new Button("Apple");
b2=new Button("Boy");
b3=new Button("Cat");
b1.addActionListener(this);
add(b1,”card1”); add(b2,”card2”); add(b3,”card3”); }
public void actionPerformed(ActionEvent e) {
card.next(this);
}
public static void main(String[] args) {
CardLayoutExample cl=new CardLayoutExample();
cl.setSize(400,400);
cl.setVisible(true);
} }

GridBagLayout
• Each GridBagLayout object maintains a dynamic
rectangular grid of cells, with each component
occupying one or more cells, called its display
area.
• Each component managed by a grid bag layout is
associated with an instance of GridBagConstraints
that specifies how the component is laid out
within its display area.

• For customize a GridBagConstraints object by
setting one or more of its instance variables:
• gridx, gridy: Specifies the cell at the upper left of
the component's display area, where the upper-left-
most cell has address gridx = 0, gridy = 0.
• gridwidth, gridheight: Specifies the number of cells
in a row (for gridwidth) or column (for gridheight)
in the component's display area. The default value
is 1.
• fill: Used when the component's display area is
larger than the component's requested size to
determine whether (and how) to resize the
component.

import java.awt.*;
import java.util.*;
import java.applet.Applet;
public class GridBagEx1 extends Applet {
protected void makebutton(String name,
GridBagLayout gridbag,
GridBagConstraints c) {
Button button = new Button(name);
gridbag.setConstraints(button, c);
add(button);
}
public void init() {
GridBagLayout gridbag = new GridBagLayout();
GridBagConstraints c = new GridBagConstraints();
setLayout(gridbag);

c.fill = GridBagConstraints.BOTH;
c.weightx = 1.0;
makebutton("Button1", gridbag, c);
c.gridwidth = GridBagConstraints.REMAINDER; //end row
c.weightx = 0.0; //reset to the default
makebutton("Button5", gridbag, c); //another row
}
public static void main(String args[]) {
Frame f = new Frame("GridBag Layout Example");
GridBagEx1 ex1 = new GridBagEx1();
ex1.init(); f.add("Center", ex1); f.pack();
f.resize(f.preferredSize());
f.show(); } }

Menu Bars and Menus
• A menu bar displays a list of top-level menu
choices. Each choice is associated with a dropdown
menu.
• This concept is implemented in Java by the
following classes:
• MenuBar, Menu, and MenuItem.
• In general, a menu bar contains one or more Menu
objects. Each Menu object contains a list of
MenuItem objects. Each MenuItem object
represents something that can be selected by the
user.

• MenuBar Class Defines only default constructor.
• Menu Class Constructors
• Menu( )
• Menu(String optionName)
• Menu(String optionName, boolean removable)
• Here, optionName specifies the name of the menu
selection.
• Individual menu items constructors:
• MenuItem( )
• MenuItem(String itemName)
• MenuItem(String itemName, MenuShortcut
keyAccel)

Methods
• Disable or enable a menu item by using:
• void setEnabled(boolean enabledFlag)
• boolean isEnabled( )
• Label set and get using:
• void setLabel(String newName)
• String getLabel( )
• Checkable menu item by using a subclass of
MenuItem called CheckboxMenuItem. :
• CheckboxMenuItem( )
• CheckboxMenuItem(String itemName)
• CheckboxMenuItem(String itemName, boolean on)

Methods
• Status about checkable MenuItem:
• boolean getState( )
• void setState(boolean checked)
• For add MenuItem:
• MenuItem add(MenuItem item)
• For add MenuBar
• Menu add(Menu menu)
• To get Item from Menu:
• Object getItem( )

DialogBox
• Dialog boxes are primarily used to obtain user input.
• They are similar to frame windows, except that
dialog boxes are always child windows of a top-level
window.
• Dialog boxes don’t have menu bars.
• In other respects, dialog boxes function like frame
windows.
• Dialog boxes may be modal or modeless.
• When a modal dialog box is active, all input is
directed to it until it is closed.
• When a modeless dialog box is active, input focus can
be directed to another window in your program.

• Constructors:.
• Dialog(Frame parentWindow, boolean mode)
• Dialog(Frame parentWindow, String title,
boolean mode)
• To create Dialog Box:
• Create Frame or Applet
• Create another class which extends Dialog class.
• Call this new class from Frame/Applet class.
• In constructor of Extended Dialog class, use
super method and pass vales to constructor of
Dialog

import java.awt.*;
import java.awt.event.*;
public class DialogExample {
private static Dialog d;
DialogExample() {
Frame f= new Frame();
d = new Dialog(f , "Dialog Example", true);
d.setLayout( new FlowLayout() );
Button b = new Button ("OK");
b.addActionListener ( new ActionListener()
{ public void actionPerformed( ActionEvent e )
{ DialogExample.d.setVisible(false); }
});
d.add( new Label ("Click button to continue."));
d.add(b); d.setSize(300,300);
d.setVisible(true); }

FileDialog
• Java provides a built-in dialog box that lets the user
specify a file.
• To create a file dialog box, instantiate an object of
type FileDialog.
• Constructor:
• FileDialog(Frame parent, String boxName)
• FileDialog(Frame parent, String boxName, int how)
• FileDialog(Frame parent)
• Int how: FileDialog.LOAD, FileDialog.SAVE
• Methods:
• String getDirectory( )
• String getFile( )

import java.awt.*;
class SampleFrame extends Frame
{
SampleFrame(String title){
super(title); }}
class FileDialogDemo
{public static void main(String args[]){
Frame f = new SampleFrame("File Dialog Demo");
f.setVisible(true);
f.setSize(100, 100);
FileDialog fd = new FileDialog(f, "File Dialog");
fd.setVisible(true);
}}

�ݺ�ߣ

events,key,life cycle-abstract window tool kit,abstract class

More Related Content

events,key,life cycle-abstract window tool kit,abstract class