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Chapter 13: Advanced GUIs and Graphics
Java Programming: Program Design Including Data Structures
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Chapter Objectives Learn about applets Explore the class Graphics
Learn about the class Font Explore the class Color Java Programming: Program Design Including Data Structures
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Chapter Objectives (continued)
Learn to use additional layout managers Become familiar with more GUI components Learn how to create menu-based programs Explore how to handle key and mouse events Java Programming: Program Design Including Data Structures
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Inheritance Hierarchy of GUI Classes
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Constructors and Methods of the class Component
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Constructors and Methods of the class Component
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Constructors and Methods of the class Component
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Constructors and Methods of the class Component
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Applets A Java program that is embedded within a Web page and executed by a Web browser Create an applet by extending the class JApplet class JApplet is contained in package javax.swing Java Programming: Program Design Including Data Structures
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Applets Java Programming: Program Design Including Data Structures
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Applets (continued) Java Programming: Program Design Including Data Structures
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Applets (continued) No main method
Methods init, start, and paint guaranteed to be invoked in sequence To develop an applet: Override any/all of the methods above Java Programming: Program Design Including Data Structures
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Applet Methods init method: paint method: Initializes variables
Gets data from user Places various GUI components paint method: Performs output Java Programming: Program Design Including Data Structures
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Skeleton of a Java Applet
import java.awt.Graphics; import javax.swing.JApplet; public class WelcomeApplet extends JApplet { } Java Programming: Program Design Including Data Structures
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Applet Displaying Welcome Message
//Welcome Applet import java.awt.Graphics; import javax.swing.JApplet; public class WelcomeApplet extends JApplet { public void paint(Graphics g) super.paint(g); //Line 1 g.drawString("Welcome to Java Programming" , 30, 30); //Line 2 } Java Programming: Program Design Including Data Structures
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HTML to Run Applet Java Programming: Program Design Including Data Structures
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class Font Shows text in different fonts Contained in package java.awt
Available fonts: Serif/Sans Serif Monospaced Dialog/DialogInput Arguments for constructor: String specifying the font face name int value specifying font style int value specifying font size Expressed in points (72 points = 1 inch) Java Programming: Program Design Including Data Structures
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class Font (continued)
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class Color Shows text in different colors
Changes background color of component Contained in package java.awt Java Programming: Program Design Including Data Structures
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class Color (continued)
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class Color (continued)
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class Color (continued)
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class Graphics Provides methods for drawing items such as lines, ovals, and rectangles on the screen Contains methods to set the properties of graphic elements including clipping areas, fonts, and colors Contained in the package java.awt Java Programming: Program Design Including Data Structures
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class Graphics Java Programming: Program Design Including Data Structures
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Constructors and Methods for the class Graphics
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Constructors and Methods for the class Graphics
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Constructors and Methods for the class Graphics
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Constructors and Methods for the class Graphics
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Differences Between Applets and GUI Applications
Derived from JApplet No main method Uses init method Displayed by HTML Sets title in HTML Size set in HTML Applet closes when HTML doc closes GUI applications Class extends JFrame Invokes main method Uses constructors Uses method setVisible Uses setTitle method Uses method setSize Closes with Exit button Java Programming: Program Design Including Data Structures
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Converting a GUI Application to an Applet
Change JFrame to JApplet Change constructor to method init Remove method calls such as setVisible, setTitle, setSize Remove the method main If applicable, remove Exit button and all code associated with it (for example, action listener) Java Programming: Program Design Including Data Structures
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Additional GUI Components
JTextArea JCheckBox JRadioButton JComboBox JList Java Programming: Program Design Including Data Structures
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JTextArea Can collect multiple lines of input from user
Can display multiple lines of output Pressing Enter key separates lines of text Each line ends with newline character (\n) Derived from class JTextComponent Java Programming: Program Design Including Data Structures
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JTextArea Java Programming: Program Design Including Data Structures
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JTextArea (continued)
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JTextArea Example Java Programming: Program Design Including Data Structures
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JCheckBox User selects from predefined values
Example of a toggle button Clicking JCheckBox generates item event Use interface ItemListener and its abstract method itemStateChanged to handle event Java Programming: Program Design Including Data Structures
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JCheckBox Java Programming: Program Design Including Data Structures
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Constructors and Methods of class JCheckBox
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Constructors and Methods of class JCheckBox
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JRadioButton Created same way as check boxes
Placed in content pane of applet Forces user to select only one radion button at a time You create a button group to group radio buttons Generates an ItemEvent interface ItemListener and method itemStateChanged used to handle events Java Programming: Program Design Including Data Structures
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JRadioButton Java Programming: Program Design Including Data Structures
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JRadioButton Java Programming: Program Design Including Data Structures
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JComboBox Commonly known as a drop-down list
Used to select an item from a list of possibilities Generates an ItemEvent Event monitored by ItemListener ItemListener invokes method itemStateChanged. Java Programming: Program Design Including Data Structures
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JComboBox (continued)
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JComboBox (continued)
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JList Java Programming: Program Design Including Data Structures
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JList (continued) Java Programming: Program Design Including Data Structures
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Layout Managers FlowLayout GridLayout Default layout manager
Places components from left to right until no more items can be placed Can align each line left, center, or right Default alignment: LEFT GridLayout Similar to FlowLayout All rows (columns) have same number of components All components have the same size Java Programming: Program Design Including Data Structures
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Layout Managers (continued)
BorderLayout Items placed into one of five specific regions: NORTH/SOUTH EAST/WEST CENTER NORTH and SOUTH components extend horizontally (completely span one edge to the other) EAST and WEST components extend vertically between components in NORTH and SOUTH regions CENTER component expands to occupy any unused regions Java Programming: Program Design Including Data Structures
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Menus Allow for various functions without cluttering GUI with too many components Can be attached to objects such as JFrame and JApplet (setJMenuBar method) To set a menu bar: private JMenuBar menuMB = new JMenuBar(); setJMenuBar(menuMB); Add menus to menu bar; add menu items to menu Order of menus added = order of appearance Java Programming: Program Design Including Data Structures
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Keyboard and Mouse Events
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Chapter Summary Creating applets class Font class Graphics class Color
Differences between applets and GUI applications Converting GUI applications to applets Java Programming: Program Design Including Data Structures
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Chapter Summary (continued)
GUI components: JTextArea JCheckBox JRadioButton Layout managers Menus Keyboard and mouse events Java Programming: Program Design Including Data Structures
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