Components

1
Components

• A Light Overview of the A.W.T.

2
Overview

• Definition of components
• A look at two common components
• Buttons
• Textfields
• Methods of all components

3
What is a Component

• The A.W.T. (Abstract Windowing Toolkit) is where
  graphical things live
• Buttons
• TextFields
• TextAreas
• Graphics
• Scrollbars
• Checkboxes

4
What is a Component

• The A.W.T. (Abstract Windowing Toolkit) is where
  graphical things live
• Buttons
• TextFields
• TextAreas
• Graphics
• Scrollbars
• Checkboxes

All of these things are components, and inherit
from class Component
5
SO

• Components are just graphical widgets used to
  build GUIs (Graphical User Interfaces)
• Most of the things in windows are components
• If you know one, you know them all
• Well focus on two common ones
• Button
• TextField
• Components have tons of accessors and modifier
  method (for querying)

6
Getting Components into Your Applet

• Steps
• Declare the component as an attribute of the
  applet
• Bring the component to life (using new)
• add( ) the component
• // Note 2 and 3 are usually done in init ( )

7
The Button

• There is a Button class
• Push Buttons for some kind of action to occur
• Its constructor expects a String (a label for
  the Button)
• Example
• Button b
• b new Button (Push me and DIE)
• Size of Button depends on the text on it (and
  some other things)

8
TextFields

• There is a TextField class
• Used to type in a single line of text
• Constructor expects an int representing the
  number of characters
• Example
• TextField t
• t new TextField (30)
• Important methods
• getText ( )
• setText ( )

9
Example

• import java.awt.
• public class Worthless extends java.applet.Applet
  
• Button b
• TextField t
• public void init ( )
• b new Button (Press me and DIE)
• t new TextField (30)

10
Bad Example!

• import java.awt.
• public class Worthless extends java.applet.Applet
  
• Button b
• TextField t
• public void init ( )
• b new Button (Press me and DIE)
• t new TextField (30)
• // The user wont see the button or textfield!
• // forgot to add the components!

11
Adding the Components

• import java.awt.
• public class RockOn extends java.applet.Applet
• Button b
• Textfield t
• public void init ( )
• b new Button (Press me and DIE)
• t new Textfield (30)
• add ( b )
• add ( t )

12
Methods all Components Have

• setBackground ( Color c )
• setForeground ( Color c )
• setEnabled ( boolean b )
• setVisible ( boolean b )
• // Check the API for Component to see other
• // functionality

13
Example

• import java.awt.
• public class Xmas extends java.applet.Applet
• Button b
• TextField t
• public void init ( )
• b new Button (Press)
• t new TextField (30)
• b.setBackground (Color.green)
• b.setForeground (Color.red) // red text label
• t.setBackground (Color.blue)
• add ( b )
• add ( t )

14
Output
15
Summary

• Components are widgets
• Including components into applets
• Declare the component
• Bring component to life
• Add the component
• Components have accessors and modifiers to get
  their state (later)
• You should now explore other components