Awt

Rakesh Ravaso Patil
Dept. of Computer Engg.
T.E. „B‟ 12276

Overview…
 Introduction to AWT
 Swing vs. AWT
 Building GUI
 Component Hierarchy
 AWT Control Fundamentals
 Adding Components
 Arranging Components
 Overview of Event Handling
 Working with Graphics
 Conclusion

AWT (Abstract Window Toolkit)
 Present in all Java implementations

 Adequate for many applications

 Uses the controls defined by your OS

 Difficult to build an attractive GUI

 import java.awt.*;
 import java.awt.event.*;

Swing
 Same concepts as AWT
 Doesn‟t work in ancient Java implementations (Java
1.1 and earlier)
 Many more controls, and they are more flexible
 Some controls, but not all, are a lot more complicated
 Gives a choice of “look and feel” packages
 Much easier to build an attractive GUI
 import javax.swing.*;

Swing vs. AWT
 Swing is bigger, slower, and more complicated
 But not as slow as it used to be
 Swing is more flexible and better looking
 Swing and AWT are incompatible--you can use
either, but you can‟t mix them
 Actually, you can, but it‟s tricky and not worth doing
 Learning the AWT is a good start on learning Swing
 Many of the most common controls are just renamed
 AWT: Button b = new Button ("OK");
 Swing: JButton b = new JButton("OK");

To build a GUI...
 Create some Components, such as buttons, text
areas, panels, etc.
 Add your Components to your display area
 Arrange, or lay out, your Components
 Attach Listeners to your Components
 Interacting with a Component causes an Event to occur
 A Listener gets a message when an interesting event
occurs, and executes some code to deal with it

An Applet is Panel is Container
java.lang.Object
|
+----java.awt.Component
|
+----java.awt.Container
|
+----java.awt.Panel
|
+----java.applet.Applet
…so you can display things in an Applet

Example: A "Life" applet
Container (Applet)

Containers (Panels)

Component (Canvas)

Components (Buttons)

Components (TextFields)

Components (Labels)

Some types of components
Label Button Checkbox

Choice Scrollbar

TextField List TextArea

Button

Checkbox CheckboxGroup

Creating components
 Label lab = new Label ("Hi, Dave!");
 Button but = new Button ("Click me!");
 Checkbox toggle = new Checkbox ("toggle");
 TextField txt =
new TextField ("Initial text.", 20);
 Scrollbar scrolly = new Scrollbar
(Scrollbar.HORIZONTAL, initialValue,
bubbleSize, minValue, maxValue);

Adding components to the Applet
class MyApplet extends Applet {
public void init () {
add (lab); // same as this.add(lab)
add (but);
add (toggle);
add (txt);
add (scrolly);
...

Arranging components
 Every Container has a layout manager
 The default layout for a Panel is FlowLayout
 An Applet is a Panel
 Therefore, the default layout for a Applet is
FlowLayout
 You could set it explicitly with
setLayout (new FlowLayout( ));
 You could change it to some other layout manager

Flow Layout
 Use add(component); to add to a
component when using a
FlowLayout
 Components are added left-to-right
 If no room, a new row is started
 Exact layout depends on size of
Applet
 Components are made as small as
possible
 FlowLayout is convenient but often
ugly

BorderLayout
 At most five components
can be added
 If you want more
components, add a
Panel, then add
components to it.
•setLayout (new BorderLayout());

GridLayout
 The GridLayout
manager divides the
container up into a
given number of rows
and columns:
 new GridLayout(rows,
columns)

•All sections of the grid are equally sized and as
large as possible

Making components active
 Most components already appear to do something--
buttons click, text appears
 To associate an action with a component, attach a
listener to it
 Components send events, listeners listen for events
 Different components may send different events, and
require different listeners

Listeners
 Listeners are interfaces, not classes
 class MyButtonListener implements
ActionListener {
 An interface is a group of methods that must be
supplied
 When you say implements, you are promising to
supply those methods

Writing a Listener
 For a Button, you need an ActionListener

b1.addActionListener
(new MyButtonListener ( ));

 An ActionListener must have an
actionPerformed(ActionEvent) method

public void actionPerformed(ActionEvent e) {
…
}

Listeners for TextFields
 An ActionListener listens for someone hitting the
Enter key
 An ActionListener requires this method:
public void actionPerformed (ActionEvent e)
 You can use getText( ) to get the text

 A TextListener listens for any and all keys
 A TextListener requires this method:
public void textValueChanged(TextEvent e)

Working With Graphics
Circle Triangle
Rounded
Rectangle Arc

Ellipse

Rectangle
Lines

Working with Graphics
 void drawLine(int x1, int y1, int x2, int y2)
 void drawRect(int top, int left, int width, int height)
 void drawRoundRect(int top, int left,int width, int
height, int xDiam, int yDiam)
 void drawOvel(int top, int left, int width, int height)
 void drawArc(int top, int left, int width,int height, int
startAngle, int sweepAngle)
 void drawPoly(int x[], int y[], int numPoints)

 void fill….

Format Shape
 Working with colors
 HSB
 RGB
 static int HSBtoRGB(float hue, float saturation, float
brightness)
 Static float[] RGBtoHSB(int red, int green, int blue,
float value[])
 Working with Fonts
 Font(String fontName, int fontStyle, int pointSize)

Summary : Building a GUI
 Create a container, such as Frame or Applet
 Choose a layout manager
 Create more complex layouts by adding Panels; each
Panel can have its own layout manager
 Create other components and add them to whichever
Panels you like
 For each active component, look up what kind of
Listeners it can have
 Create (implement) the Listeners
 often there is one Listener for each active component

Summary: Building a GUI
 For each Listener you implement, supply the
methods that it requires
 For Applets, write the necessary HTML
 Graphics
 Drawing Lines
 Drawing Rectangles
 Drawing Ellipse and Circles
 Drawing Polygons
 Color schemes and Fonts

Awt

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Awt