06 intro eclipse, applets, graphics

8/4/2019 06 Intro Eclipse, Applets, Graphics

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Carnegie Mellon

Topics in Software Engineering

Lynn Robert Carter

2008-05-12

Copyright 2008, Lynn Robert Carter

Classes: Fields, Methods, and Constructors


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Carnegie Mellon Topics in Software EngineeringJava: Introduction to Eclipse, Applets, and Graphics2

Agenda

Introduction to Eclipse

Applets

Graphics


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Carnegie Mellon Topics in Software EngineeringJava: Introduction to Eclipse, Applets, and Graphics

Starting Eclipse


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Selecting a workspace


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The Welcome Screen-1


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The Welcome Screen-2


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The workbench



Creating a new Java Project-1



Creating a new Java Project-2


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The Create a Java project wizard-1


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The Create a Java project wizard-2


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The updated workbench-1


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Expanding the project folders


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Select the src folder


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Create a Package-1


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Create a Package-2


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The New Java Package wizard-1


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The New Java Package wizard-2


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The updated workbench


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Create a new class-1


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Create a new class-2


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The New Java Class wizard-1


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Removing the TODO task tag


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Carnegie MellonTopics in Software Engineering

Java: Introduction to Eclipse, Applets, and Graphics

Entering the Java program-1


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Entering the Java program-2


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Save the edit changes


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Running the program


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The results


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Java: Introduction to Eclipse, Applets, and Graphics35

Agenda


Applets

Graphics


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Introduction to Applets-1

An applet is a small application that resides withinsome other parent application

Web browsers are common parent applications for applets

Applets allow web pages to be dynamic and interactive

Eclipse supports the development of both applicationsand applets with a process that starts out exactly thesame

1. Create a new Java Project and give it a helpful name

2. Within the Java Project folder, find the src folder

3. Create a properly named Java Package within the src folder


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Introduction to Applets-2

Unlike an application, an Applet does not have amain method, so do not ask Eclipse to create onefor you when you create the Class within the justcreated Java Package

The class that roots the Applet must extend theJApplet class and must contain a method namedpaint


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The default class Applet


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Enhancing the default class


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Alternatives suggested by Eclipse


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Adding the import statement


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The cause of the warning


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Changing the warning settings

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Right click on the

package icon

Select the Properties item

from the pop-up menu


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Changing the default properties-1


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Creating the application


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Running the Applet


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The resulting Applet window-1


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The resulting Applet window-2


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Java: Introduction to Eclipse, Applets, and Graphics55

Agenda


Applets

Graphics


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Introduction to graphics-1

Unlike most languages before it, support forgraphics has been a part of Java from nearly its

beginning

Graphics is supported by means of two Class

libraries

The Abstract Windowing Toolkit (AWT)

Swing


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Introduction to graphics-2

AWT was first and it provided support for Windows and allowing the user to change the size/shape

Layout management (to support repositioning and changingthe size an shape of components within a window, when

the size and shape of the window changes, so theinformation in the window is still useful)

Widgets to support interactions between the program and ausers (widgets facilitated graphics input/output)

Swing came later and added a moresophisticated layer to the AWT and enhancedJava graphics programs


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The Abstract Windowing Toolkit

Set of user interface components

Event-handling routines for currently popularwindow and point and click user interfaces

Tools for drawing and displaying images

Facilities for drawing shapes and using colors

Routines for handling characters (fonts, styles, etc.)

Layout managers for dealing with user changes to thesize and shape of the window


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Swing

Focused on platform independence

Designed to be extensible

Component-based framework

Designed to be customizable

Lightweight user-interface that does not try to use thetools of the underlying hosts operating system

Loosely-coupled architecture (patterned after themodel / view/ controller architecture model)


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Graphics within Applets-1

Graphics can be done from within bothApplets and regular Java applications

Setting up regular applications to do graphics

requires quite a great deal of glue code and

so we will defer that until a later lecture


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Graphics within Applets-2

Applets depend upon an Applet Viewer program or aweb browser to support graphics This interface means that none of the glue code required by regular

applications is needed

Once the glue code has been provided, all of the code within an Applet

can be used in regular applications, so learning how to do graphics inApplets is transferable to applications

The paint() method is the heart of an graphicsprogram

When a window must be drawn, the paint() methodis called to perform that operation


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The implementation process-1

Creating graphics programs is similar to givingspecific instructions to someone who is doing

work for you

Start with a blank piece of paper, a canvas

Design the solution

Transform the design into code


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The implementation process-2

Design the solution What components need to be placed onto the canvas?

Where should the components be placed?

What size should the components be?

Select colors, line sizes, character fonts, character styles asrequired to create a useful design

Transform the design to code

Determine the code required to produce each component

Determine the location of this component on the canvasusing the coordinate system of the canvas

Determine the other parameters that the design requires


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The graphics canvas


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The graphics components

Output components lines

shapes (rectangles, ovals, arcs, polygons)

strings

images

Input components buttons (standalone, radio buttons, check box) sliders

text field

text area

menus

combo boxes

Structuring components windows, frames, view ports, layout managers

lists, trees


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A small graphics Appletimportjavax.swing.JApplet;

importjava.awt.Color;importjava.awt.Graphics;

public class Mainline extends JApplet {

public void paint(Graphics g){super.paint( g );g.drawRect(50, 50, 100, 100);g.drawRect(75, 75, 100, 100);g.setColor(Color.BLUE);g.fillRect(100, 50, 100, 100);g.setColor(Color.BLACK);g.fillRect(125, 75, 100, 100);

}}


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The results of running the Applet


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Agenda


Applets

Graphics

06 intro eclipse, applets, graphics

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