chapter 13: advanced guis and graphics j ava p rogramming: from problem analysis to program design,...

Chapter 13: Advanced GUIs Chapter 13: Advanced GUIs and Graphicsand Graphics

JJavaava PProgramming:rogramming:

From Problem Analysis to Program From Problem Analysis to Program Design,Design, Second EditionSecond Edition

Java Programming: From Problem Analysis to Program Design, Second Edition 2

Chapter Objectives Learn about applets. Explore the class Graphics. Learn about the class Font. Explore the class Color. 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.


Inheritance Hierarchy of GUI Classes


Constructors and Methods of the class Component


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.


Applets


Applets

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.


Applet Methods init method:

Initializes variables.

Gets data from user.

Places various GUI components.

paint method:

Performs output.


Skeleton of a Java Applet

import java.awt.Graphics;import javax.swing.JApplet;

public class WelcomeApplet extends JApplet{

}


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 }}


HTML to Run Applet


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) .


class Font


class Color

Shows text in different colors.

Changes background color of component.

Contained in package java.awt.


class Color


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.


class Graphics


Constructors and Methods for the class Graphics


Differences Between Applets and GUI Applications

Applets

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.


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).


Additional GUI Components

JTextArea

JCheckBox

JRadioButton

JComboBox

JList


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.


JTextArea


JTextArea Example


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.


JCheckBox


Constructors and Methods of class JCheckBox


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.


JRadioButton


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.


JComboBox


JList


Layout Managers FlowLayout

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.


Layout Managers 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.


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.


Keyboard and Mouse Events


Chapter Summary

Creating applets

class Font

class Graphics

class Color

Differences between applets and GUI applications

Converting GUI applications to applets


Chapter Summary

GUI components:

JTextArea

JCheckBox

JRadioButton

Layout managers

Menus

Keyboard and mouse events

chapter 13: advanced guis and graphics j ava p rogramming: from problem analysis to program design,...

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