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Sunday 6 August 2017

Java components

Definition of Java Components : A graphical user interface is composed of individual building blocks such as push buttons, scrollbars... thumbnail 1 summary
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Definition of Java Components :

  • A graphical user interface is composed of individual building blocks such as push buttons, scrollbars, and pull-down menus.
  • Some programmers know these individual building blocks as controls, while others call them widgets.
  • In Java, they are typically called components because they all inherit from the base class java.awt.Component.
  • When you are describing a GUI toolkit, one of the most important characteristics is the list of components it supports. 
  • lists the heavyweight components provided by AWT, where heavyweight refers to components that are layered on top of native GUI components. 
  • The components listed are all classes in the java.awt package. 
  • One of the curious features of the AWT is that pull-down and pop-up menus, and the items contained within those menus, are not technically components. 
  • Instead of inheriting from Component, they inherit from java.awt. MenuComponent. 
  • Nevertheless, the various menu component classes are used in very much the same way that true components are.
Properties of Java Components
  • A Component object represents a graphical interactive area displayable on the screen that can be used by the user.
  • Any subclass of a Component class is known as a component. For example, button is a component.
  • Only components can be added to a container, like frame.

Component Name
Description
Button
A graphical push button.
Canvas
A heavyweight component that displays a blank canvas, allowing a program to display custom graphics.
Checkbox
A toggle button that can be selected or unselected. Use the Checkbox group to enforce mutually exclusive or radio button behavior among a group of Checkbox components.
CheckboxMenuItem
A toggle button that can appear within a Menu.
Choice
An option menu or drop-down list. Displays a menu of options when clicked on and allows the user to select among this fixed set of options.
Component
The base class for all AWT and Swing components. Defines many basic methods inherited by all components.
FileDialog
Allows the user to browse the filesystem and select or enter a filename.
Label
Displays a single line of read-only text. Does not respond to user input in any way.
List
Displays a list of choices (optionally scrollable) to the user and allows the user to select one or more of them.
Menu
A single pane of a pull-down menu
MenuBar
A horizontal bar that contains pull-down menus.
MenuComponent
The base class from which all menu-related classes inherit.
MenuItem
A single item within a pull-down or pop-up menu pane.
PopUpMenu
A menu pane for a pop-up menu.
Scrollbar
A graphical scrollbar.
TextArea
Displays multiple lines of plain text and allows the user to edit the text.
TextComponent
The base class for both TextArea and TextField.
TextField
Displays a single line of plain text and allows the user to edit the text.