AWT (Abstract Window Toolkit) controls.pptx

AWT (Abstract Window Toolkit) controls are pre-built GUI components from Java's AWT library that allow users to interact with an application, such as Buttons, Labels, Text Fields, and Checkboxes. These controls are used to build graphical user interfaces (GUIs) and are fundamental for creating a user-friendly application by providing elements for input, output, and user actions.

1. AWT - A bstract W indowing T oolkit 1

2. Objectives Describe Abstract Windowing Toolkit (AWT ) Discuss Containers and Components Frame Panel Label TextFields and TextAreas Checkboxes and RadioButtons Choice Identify events generated by components Create a standalone AWT application 2

3. 1. Introduction As on date, software applications have become user-friendlier because of introducing graphics in user interfaces. These make the language richer in terms of creating graphical objects that can be controlled by the developer as well as the user. One of the most important outcomes of this is that languages have happened to be GUI based . 3

4. 2. Abstract Windowing Toolkit Graphical User Interface (GUI) is used to accept input through a keyboard or a mouse. Abstract Windowing Toolkit (AWT) is a set of Java classes that allow us to create a GUI. AWT provides items which enable creation of an attractive and efficient GUI. 4

5. 3. Hierarchy of classes in Java Component Button Checkbox Container Choice Canvas TextComponent Label Panel Window Applet Frame Dialog TextArea TextField 5

6. 3.1 Containers An area that can hold elements. It can be drawn or painted. Container class in the java.awt package directly or indirectly derives two commonly used containers – Frame and Panel. Frame is a separate window and has borders. Panel is an area without borders and is contained within a window. 6

7. 3.1 Containers - Frame A window that is independent of an applet and of the browser. Can be a component or a container. Can be created using constructors Some of these constructors are: Frame() Creates a Frame which is invisible Frame(String Title) Creates an invisible Frame with given title 7

8. 3.1 Containers – Frame Example Output 8

9. 3.2 Panel Used to group a number of components together. Simplest way to create a panel is through its constructor Panel( ) . A panel has to be added to a frame. The frame will be visible only when the two methods – setSize ( ) and setVisible ( ) are set. 9

10. 3.2 Panel Example Output 10

11. 3.3 Component Anything that can be placed on a user interface and can be made visible or resized. Examples include textfields , labels, checkboxes, textareas etc. Some advanced components include scrollbars, scrollpanes and dialogs. 11

12. 4. Various components Label Text field Checkbox Radio button Button Text Area 12

13. 4.1 Label Generally used to indicate the purpose of an item. Not user-editable . Can be created using one of the following constructors: Label( ) Creates an empty label Label(String labeltext ) Creates a label with a given text Label(String labeltext , int alignment) Creates a label with given alignment where alignment can be Label.LEFT , Label.RIGHT or Label.CENTER 13

14. 4.2 Textfield GUI element used to input text. Generally accepts one line of input. Can be created using one of the following constructors: Textfield () Creates a new textfield Textfield ( int columns) Creates a new textfield with given number of columns Textfield (String s) Creates a new textfield with the given string Textfield (String s, int columns) Creates a new textfield with given string and given number of columns 14

15. 4.2 Textfield : Example Output 15

16. 4.3 TextArea Used when text is to be accepted has two or more lines. Includes a scrollbar. TextArea can be created using some of the following constructors given below: TextArea ( ) Creates a new TextArea TextArea ( int rows, int cols) Creates a new TextArea with given number of rows and columns TextArea (String text, int rows, int cols) Creates a new TextArea with given string, given number of rows and columns 16

17. 4.3 TextArea : Example Output 17

18. 4.4 Button Part of GUI. The easiest way to trap user action. Can create buttons in Java using any of the following constructors. Button() Creates a new Button . Button(String text) Creates a new Button with the given String 18

19. 4.4 Button : Example Output 19

20. 4.5 Checkbox Used for multi-option user input that the user may select or deselect by clicking them. Checkboxes in Java can be created using constructors . Some of these constructors are: Checkbox() Creates an empty textbox Checkbox(String text) Creates a checkbox with given string as label 20

21. 4.5 Checkbox: Example Output 21

22. 4.6 Radiobuttons Used as option button to specify choices. Only one button in a radiobutton group can be selected . First create a CheckboxGroup object CheckboxGroup cg=new CheckboxGroup (); Then create each of the radio buttons Checkbox male=Checkbox(“male”, cg,true ); Checkbox female=Checkbox(“female”, cg,false ); 22

23. 4.6 Radiobuttons : Example Output 23

24. 4.7 Lists Displays a list of choices to the user. User may select one or more items. Created using a number of strings or text values. Choice class enables us to create multiple item lists Choice moviestars =new Choice (); Add items using the addItem () method moviestars.addItem (“Antonio Banderas”); moviestars.addItem (“Leonardo Dicaprio ”); 24

25. 4.7 Lists : Example Output 25

26. Event handling with components An event is generated whenever a user clicks a mouse, presses or releases a key. Event Delegation Model is used to handle events. This process allows the program to register handlers called ‘ listeners ’ with objects whose events need to be captured. Handlers are automatically called when an event takes place. 26

27. Event handling with components ... Event listeners are implemented as interfaces in Java. Steps to be followed – Associate the class with the appropriate listener interface Identify all components that generate events Identify all events to be handled Implement the methods of the listener and write the event handling code within the methods 27

28. Event handling with components ... Event Class Description Interface ActionEvent Button is pressed, list item is double clicked or a menu is selected ActionListener AdjustmentEvent When scrollbar is used AdjustmentListener ComponentEvent Component is resized, moved, hidden or made visible ComponentListener FocusEvent Component gains or loses keyboard focus FocusListener

29. Event handling with components ... Event Class Description Interface ItemEvent When a menu item is selected or deselected or when a checkbox or list item is clicked ItemListener WindowEvent Window is activated, closed, opened or quit WindowListener TextEvent Value of a text field or text area is changed TextListener MouseEvent Mouse is moved, clicked, dragged or released MouseListener Mouse MotionListener KeyEvent Input is received from the keyboard KeyListener