TweetFollow Us on Twitter

Jan 97 Getting Started

Volume Number: 13 (1997)
Issue Number: 1
Column Tag: Getting Started

Java's AWT Shapes

By Dave Mark

Two of the first things any Mac programmer learns are the concept of event-loop programming and drawing using QuickDraw. The Java programming learning curve is quite similar in this respect. Last month, we introduced Java's event handling mechanism. This month, we'll explore the java.awt.Graphics class. Specifically, we'll look at the java.awt.Graphics member functions that allow you to draw shapes in your applet window.

The java.awt.Graphics Shapes

This month's applet is called javaDraw. Before you dig into the code, take some time to read the java.awt.Graphics web page (part of the JDK API Documentation from Sun.) Pay special attention to the function names that start with either the words draw or frame. The draw routines are analogous to the QuickDraw paint routines (like PaintRect()) and the frame routines do the same as the QuickDraw frame routines (like FrameRect()).

Creating the javaDraw Project

Create a new project called javaDraw.µ using the Java applet stationery. Create a new source code file named javaDraw.html and add it to the project (replace any existing html file that may have been added to the project.) Here's the html code:

<title>javaDraw</title>
<hr>
<applet codebase="javaDraw Classes" code="javaDraw.class" width=228 height=160>
</applet>
<hr>
<a href="javaDraw.java">The source.</a>

Next, create a second source code file named javaDraw.java and add it to the project as well (replace any default .java file that may have been added to the project.) Here's the Java code:

import java.awt.*;

public class shapeCanvas extends Canvas
{
 final int  rectangle=0,
 rect3D=1,
 roundRect=2,
 arc=3,
 oval=4,
 line=5,
 polygon=6;
 int    whichShape = rectangle;
 booleanisFilled = true;
 
 shapeCanvas( int width, int height )
 {
 setBackground( Color.yellow );
 setForeground( Color.red );
 resize( width, height );
 }
 
 public void SetShape( int newShape )
 {
 whichShape = newShape;
 }
 
 public void SetIsFilled( boolean newIsFilled )
 {
 isFilled = newIsFilled;
 }
 
 public void paint( Graphics g )
 {
 Rectangler, b;
 Polygonpoly;
 
 b = bounds();
 r = new Rectangle( 10, 10, b.width - 20,
 b.height - 20 );
 
 poly = new Polygon();
 poly.addPoint( r.x, r.y );
 poly.addPoint( r.x, r.y + r.height );
 poly.addPoint( r.x + r.width, r.y + r.height );
 poly.addPoint( r.x, r.y + r.height/2 );
 poly.addPoint( r.x + r.width, r.y + r.height/2 );
 poly.addPoint( r.x, r.y );
 
 if ( isFilled )
 {
 switch ( whichShape )
 {
 case rectangle:
 g.fillRect( r.x, r.y, r.width, r.height );
 break;
 case rect3D:
 g.fill3DRect( r.x, r.y, r.width, r.height, true );
 break;
 case roundRect:
 g.fillRoundRect( r.x, r.y, r.width, r.height,
 16, 16 );
 break;
 case arc:
 g.fillArc( r.x, r.y, r.width, r.height, 0, 270 );
 break;
 case oval:
 g.fillOval( r.x, r.y, r.width, r.height );
 break;
 case line:
 g.drawLine( r.x, r.y, r.x + r.width, r.y + r.height           
 );
 break;
 case polygon:
 g.fillPolygon( poly );
 break;
 }
 }
 else
 {
 switch ( whichShape )
 {
 case rectangle:
 g.drawRect( r.x, r.y, r.width, r.height );
 break;
 case rect3D:
 g.draw3DRect( r.x, r.y, r.width, r.height, true );
 break;
 case roundRect:
 g.drawRoundRect( r.x, r.y, r.width, r.height,
 16, 16 );
 break;
 case arc:
 g.drawArc( r.x, r.y, r.width, r.height, 0, 270 );
 break;
 case oval:
 g.drawOval( r.x, r.y, r.width, r.height );
 break;
 case line:
 g.drawLine( r.x, r.y, r.x + r.width,
 r.y + r.height );
 break;
 case polygon:
 g.drawPolygon( poly );
 break;
 }
 }
 }
}

public class javaDraw extends java.applet.Applet
{
 private Choice  shapePopup, fillPopup;
 private shapeCanvas sCanvas;
 
 public void init()
 {
 shapePopup = new Choice();
 shapePopup.addItem( "Rectangle" );
 shapePopup.addItem( "3D Rectangle" );
 shapePopup.addItem( "Rounded Rectangle" );
 shapePopup.addItem( "Arc" );
 shapePopup.addItem( "Oval" );
 shapePopup.addItem( "Line" );
 shapePopup.addItem( "Polygon" );
 
 add( shapePopup );
 
 fillPopup = new Choice();
 fillPopup.addItem( "Fill Shapes" );
 fillPopup.addItem( "Do Not Fill Shapes" );
 
 add( fillPopup );
 
 sCanvas = new shapeCanvas( 208, 110 );
 add( sCanvas );
 }
 public boolean action( Event e, Object obj )
 {
 if ( e.target == shapePopup )
 {
 sCanvas.SetShape( shapePopup.getSelectedIndex() );
 sCanvas.repaint();
 
 return true;
 }
 else if ( e.target == fillPopup )
 {
 sCanvas.SetIsFilled( fillPopup.getSelectedIndex()
 == 0 );
 sCanvas.repaint();
 
 return true;
 }
 else
 return super.action( e, obj );
 }
}

If you would like to specify the application used to run your applet, select Project Settings... from CodeWarrior's Edit menu, then click on the Project/Java Project item in the scrolling list (see Figure 1.) Click on the Set... button and select your preferred applet runner from the standard get file dialog. The screen shots that I used in this column were taken using the Metrowerks Java applet runner that comes with CodeWarrior.

Figure 1. CodeWarrior's Project Setting's dialog, showing the Java Project options.

No matter what applet runner you use, be sure you specify "javaDraw Classes" in the File Name field, to match the "codebase" parameter in your html file.

Once everything is entered and set up just the way you like it, select Run from the Project menu to compile and run your applet. Figure 2 shows the javaDraw applet as it first appears. The applet area consists of two popup menus (known as choices in java-speak) and a canvas area. The top popup lets you select the type of shape you are interested in seeing, and the bottom popup lets you specify whether the shape is drawn or framed (filled or outlined.) The default setting is a filled rectangle.

Figure 2. The javaDraw applet, as it first appears.

Figure 3 shows a framed arc. Take some time to play with all the awt.Graphics shapes, in both framed and filled modes. Note that lines look the same in either mode (both call the same function) and that 3D rectangles look almost exactly the same as rectangles. I'm not sure why this last is true, but hopefully future versions of awt will implement more interesting 3D rectangles.

Figure 3. The javaDraw applet, this time showing a framed arc.

Walking Through the Source

javaDraw consists of two classes. The shapeCanvas class implements the yellow drawing canvas at the bottom of the applet area. The javaDraw class extends the applet class and initiates a shapeCanvas and the two popup menus. We'll start with the shapeCanvas class.

shapeCanvas extends the Canvas class. It starts with a series of constants specified using the final keyword. If a variable is marked as final, it becomes a constant - its initial value may not be changed. The constants represent the items in the shape popup menu. Notice that the first constant was set to zero. That's because popup menu items are zero based.

import java.awt.*;

public class shapeCanvas extends Canvas
{
 final int  rectangle=0,
 rect3D=1,
 roundRect=2,
 arc=3,
 oval=4,
 line=5,
 polygon=6;
 int    whichShape = rectangle;
 booleanisFilled = true;

The shapeCanvas() constructor sets the Canvas background and foreground colors, then sets the Canvas size to the specified width and height. SetShape() is used to set the whichShape class variable to the current shape, as specified by the popup menu. SetIsFilled() does the same thing for the isFilled boolean, setting it depending on the bottom popup menu setting.

 shapeCanvas( int width, int height )
 {
 setBackground( Color.yellow );
 setForeground( Color.red );
 resize( width, height );
 }
 
 public void SetShape( int newShape )
 {
 whichShape = newShape;
 }
 
 public void SetIsFilled( boolean newIsFilled )
 {
 isFilled = newIsFilled;
 }

The paint() method is called when the Canvas needs to be redrawn. It starts by retrieving the bounding rectangle of the Canvas. This rectangle is inset 10 pixels on each side, with the results stored in r (r is inset inside b).

 public void paint( Graphics g )
 {
 Rectangler, b;
 Polygonpoly;
 
 b = bounds();
 r = new Rectangle( 10, 10, b.width - 20,
 b.height - 20 );

Next, we create a new Polygon and add a series of points to the Polygon, creating a zigzag shape and ending at the same point we started. This last step is important since it "closes" the Polygon. The Polygon is only needed if it is actually selected from the popup. So, we should probably embed this code in the polygon case below. Sorry about my laziness!

 poly = new Polygon();
 poly.addPoint( r.x, r.y );
 poly.addPoint( r.x, r.y + r.height );
 poly.addPoint( r.x + r.width, r.y + r.height );
 poly.addPoint( r.x, r.y + r.height/2 );
 poly.addPoint( r.x + r.width, r.y + r.height/2 );
 poly.addPoint( r.x, r.y );


The rest of paint() is made up of a giant if. The first part of the if paints filled shapes. The second part of the if paints framed shapes. Take a look at each of these functions, for they are the heart and soul of the Graphics class. These are the functions that actually draw the Java shapes.

 if ( isFilled )
 {
 switch ( whichShape )
 {
 case rectangle:
 g.fillRect( r.x, r.y, r.width, r.height );
 break;
 case rect3D:
 g.fill3DRect( r.x, r.y, r.width, r.height, true );
 break;
 case roundRect:
 g.fillRoundRect( r.x, r.y, r.width, r.height,
 16, 16 );
 break;
 case arc:
 g.fillArc( r.x, r.y, r.width, r.height, 0, 270 );
 break;
 case oval:
 g.fillOval( r.x, r.y, r.width, r.height );
 break;
 case line:
 g.drawLine( r.x, r.y, r.x + r.width,
 r.y + r.height );
 break;
 case polygon:
 g.fillPolygon( poly );
 break;
 }
 }
 else
 {
 switch ( whichShape )
 {
 case rectangle:
 g.drawRect( r.x, r.y, r.width, r.height );
 break;
 case rect3D:
 g.draw3DRect( r.x, r.y, r.width, r.height, true );
 break;
 case roundRect:
 g.drawRoundRect( r.x, r.y, r.width, r.height,
 16, 16 );
 break;
 case arc:
 g.drawArc( r.x, r.y, r.width, r.height, 0, 270 );
 break;
 case oval:
 g.drawOval( r.x, r.y, r.width, r.height );
 break;
 case line:
 g.drawLine( r.x, r.y, r.x + r.width,
 r.y + r.height );
 break;
 case polygon:
 g.drawPolygon( poly );
 break;
 }
 }
 }
}

The javaDraw class implements the applet itself. The init() method first creates the shape Choice, then the fill Choice, and finally the shapeCanvas.

public class javaDraw extends java.applet.Applet
{
 private Choice  shapePopup, fillPopup;
 private shapeCanvas sCanvas;
 public void init()
 {
 shapePopup = new Choice();
 shapePopup.addItem( "Rectangle" );
 shapePopup.addItem( "3D Rectangle" );
 shapePopup.addItem( "Rounded Rectangle" );
 shapePopup.addItem( "Arc" );
 shapePopup.addItem( "Oval" );
 shapePopup.addItem( "Line" );
 shapePopup.addItem( "Polygon" );
 
 add( shapePopup );
 
 fillPopup = new Choice();
 fillPopup.addItem( "Fill Shapes" );
 fillPopup.addItem( "Do Not Fill Shapes" );
 
 add( fillPopup );
 
 sCanvas = new shapeCanvas( 208, 110 );
 add( sCanvas );
 }

The applet's action() routine checks for events occurring in either popup. If the event was in the shape Choice, the shapeCanvas' SetShape() function is called, and an update event is queued for the canvas (repaint() is similar to invalRect(), though for an entire object. If the event was the fill Choice, the SetIsFilled() method is called and the canvas is again repainted. If neither case is true, the parent class' action() method is called and that result returned.

 public boolean action( Event e, Object obj )
 {
 if ( e.target == shapePopup )
 {
 sCanvas.SetShape( shapePopup.getSelectedIndex() );
 sCanvas.repaint();
 
 return true;
 }
 else if ( e.target == fillPopup )
 {
 sCanvas.SetIsFilled( fillPopup.getSelectedIndex()
 == 0 );
 sCanvas.repaint();
 
 return true;
 }
 else
 return super.action( e, obj );
 }
}

Till Next Month...

At this point, you should have a pretty good handle on Java's graphics mechanism. Spend some time exploring the rest of the Graphics class' methods. There are some pretty funky methods in there, and we'll get to them eventually. Before I sign off, I just wanted to mention that this column marks the start of my fifth year writing for MacTech Magazine. Can you believe it? Well, here's to four more years of Mac programming fun! See you next month...

 
AAPL
$103.40
Apple Inc.
+0.93
MSFT
$44.92
Microsoft Corpora
+0.04
GOOG
$538.81
Google Inc.
+12.27

MacTech Search:
Community Search:

Software Updates via MacUpdate

Apple Security Update 2014-005 - For OS...
Apple Security Update is recommended for all users and improves the security of Mac OS X. For information on the security content of this update, please visit this website: http://support.apple.com/... Read more
EyeTV 3.6.6 - Watch and record TV on you...
EyeTV brings a rich TV experience to your Mac. Watch live TV on your Mac. Pause, rewind, and record whenever you want. EyeTV gives you powerful control over what you watch and how you watch it. Put... Read more
RapidWeaver 6.0 - Create template-based...
RapidWeaver is a next-generation Web design application to help you easily create professional-looking Web sites in minutes. No knowledge of complex code is required, RapidWeaver will take care of... Read more
NTFS 12.0.39 - Provides full read and wr...
Paragon NTFS breaks down the barriers between Windows and OS X. Paragon NTFS effectively solves the communication problems between the Mac system and NTFS, providing full read and write access to... Read more
RestoreMeNot 2.0.3 - Disable window rest...
RestoreMeNot provides a simple way to disable the window restoration for individual applications so that you can fine-tune this behavior to suit your needs. Please note that RestoreMeNot is designed... Read more
Macgo Blu-ray Player 2.10.9.1750 - Blu-r...
Macgo Mac Blu-ray Player can bring you the most unforgettable Blu-ray experience on your Mac. Overview Macgo Mac Blu-ray Player can satisfy just about every need you could possibly have in a Blu-ray... Read more
Apple iOS 8.1 - The latest version of Ap...
The latest version of iOS can be downloaded through iTunes. Apple iOS 8 comes with big updates to apps you use every day, like Messages and Photos. A whole new way to share content with your family.... Read more
TechTool Pro 7.0.5 - Hard drive and syst...
TechTool Pro is now 7, and this is the most advanced version of the acclaimed Macintosh troubleshooting utility created in its 20-year history. Micromat has redeveloped TechTool Pro 7 to be fully 64... Read more
PDFKey Pro 4.0.2 - Edit and print passwo...
PDFKey Pro can unlock PDF documents protected for printing and copying when you've forgotten your password. It can now also protect your PDF files with a password to prevent unauthorized access and/... Read more
Yasu 2.9.1 - System maintenance app; per...
Yasu was originally created with System Administrators who service large groups of workstations in mind, Yasu (Yet Another System Utility) was made to do a specific group of maintenance tasks... Read more

Latest Forum Discussions

See All

Craft Your Own Mini-Games with Papercade
Craft Your Own Mini-Games with Papercade Posted by Jessica Fisher on October 22nd, 2014 [ permalink ] iPad Only App - Designed for the iPad Scrapbookers move over, Scrapgaming is the new thing. | Read more »
Reshape Review
Reshape Review By Jennifer Allen on October 22nd, 2014 Our Rating: :: SIMPLE SHAPESUniversal App - Designed for iPhone and iPad Match triangles together to form cubes in this fast-paced and twitchy game.   | Read more »
Miika (Games)
Miika 1.0.0 Device: iOS Universal Category: Games Price: $1.99, Version: 1.0.0 (iTunes) Description: Miika is a beautiful 3D puzzle game based on camera perspectives combined with the use of optical illusions. Miika challenges... | Read more »
Infuse Pro (Photography)
Infuse Pro 3.0 Device: iOS Universal Category: Photography Price: $9.99, Version: 3.0 (iTunes) Description: ** All-new version 3 includes fully licensed and certified DTS® and DTS-HD® audio! ** | Read more »
Swap Heroes (Games)
Swap Heroes 1.0 Device: iOS Universal Category: Games Price: $.99, Version: 1.0 (iTunes) Description: **Half price for a limited time only** Swap Heroes is a casual turn-based strategy adventure. Form a group of heroes and guide them... | Read more »
Ghost Blade (Games)
Ghost Blade 1.1 Device: iOS Universal Category: Games Price: $4.99, Version: 1.1 (iTunes) Description: Get the most outstanding 3D Action Game from App Store NOW! For those who dare pursue dreams. Masterpiece of Yu Shi Game ---China... | Read more »
Fiete – A Day on a Farm Review
Fiete – A Day on a Farm Review By Amy Solomon on October 21st, 2014 Our Rating: :: A MEMORABLE EXPERIENCEUniversal App - Designed for iPhone and iPad Fiete – A day on a farm in an interactive app for young children full of... | Read more »
Tilt to Live: Gauntlet’s Revenge is Almo...
Tilt to Live: Gauntlet’s Revenge is Almost Here Posted by Jessica Fisher on October 21st, 2014 [ permalink ] One Man Left has announced the official release date of Tilt to Live: Gauntlet’s Re | Read more »
Starfly Review
Starfly Review By Jennifer Allen on October 21st, 2014 Our Rating: :: CHANGE OF PACEiPad Only App - Designed for the iPad Want a slightly different browsing experience? Starfly is a pretty personalized one but it’s also buggy.   | Read more »
Sago Mini Monsters Celebrates Halloween...
Sago Mini Monsters Celebrates Halloween with Fun Costumes and Special Treats. Posted by Jessica Fisher on October 21st, 2014 [ permal | Read more »

Price Scanner via MacPrices.net

AT&T accepting preorders for new iPads fo...
AT&T Wireless is accepting preorders for the new iPad Air 2 and iPad mini 3, cellular models, for $100 off MSRP with a 2-year service agreement: - 16GB iPad Air 2 WiFi + Cellular: $529.99 - 64GB... Read more
Apple offering refurbished Mac Pros for up to...
The Apple Store is offering Apple Certified Refurbished 2013 Mac Pros for up to $600 off the cost of new models. An Apple one-year warranty is included with each Mac Pro, and shipping is free. The... Read more
Select MacBook Airs $100 off MSRP, free shipp...
B&H Photo has 2014 a couple of MacBook Airs on sale for $100 off MSRP. Shipping is free, and B&H charges NY sales tax only. They also include free copies of Parallels Desktop and LoJack for... Read more
13-inch 2.5GHz MacBook Pro on sale for $100 o...
B&H Photo has the 13″ 2.5GHz MacBook Pro on sale for $999.99 including free shipping plus NY sales tax only. Their price is $100 off MSRP. Read more
Strong iPhone, Mac And App Store Sales Drive...
Apple on Monday announced financial results for its fiscal 2014 fourth quarter ended September 27, 2014. The Company posted quarterly revenue of $42.1 billion and quarterly net profit of $8.5 billion... Read more
Apple Posts How-To For OS X Recovery
OS X 10.7 Lion and later include OS X Recovery. This feature includes all of the tools you need to reinstall OS X, repair your disk, and even restore from a Time Machine backup. OS X Recovery... Read more
Mac OS X Versions (Builds) Supported By Vario...
Apple Support has posted a handy resource explaining which Mac OS X versions (builds) originally shipped with or are available for your computer via retail discs, downloads, or Software Update. Apple... Read more
Deals on 2011 13-inch MacBook Airs, from $649
Daily Steals has the Mid-2011 13″ 1.7GHz i5 MacBook Air (4GB/128GB) available for $699 with a 90 day warranty. The Mid-2011 13″ 1.7GHz i5 MacBook Air (4GB/128GB SSD) is available for $649 at Other... Read more
2013 15-inch 2.0GHz Retina MacBook Pro availa...
B&H Photo has leftover previous-generation 15″ 2.0GHz Retina MacBook Pros now available for $1599 including free shipping plus NY sales tax only. Their price is $400 off original MSRP. B&H... Read more
Updated iPad Prices
We’ve updated our iPad Air Price Tracker and our iPad mini Price Tracker with the latest information on prices and availability from Apple and other resellers, including the new iPad Air 2 and the... Read more

Jobs Board

Senior Event Manager, *Apple* Retail Market...
…This senior level position is responsible for leading and imagining the Apple Retail Team's global event strategy. Delivering an overarching brand story; in-store, Read more
*Apple* Solutions Consultant (ASC) - Apple (...
**Job Summary** The ASC is an Apple employee who serves as an Apple brand ambassador and influencer in a Reseller's store. The ASC's role is to grow Apple Read more
Project Manager / Business Analyst, WW *Appl...
…a senior project manager / business analyst to work within our Worldwide Apple Fulfillment Operations and the Business Process Re-engineering team. This role will work Read more
*Apple* Retail - Multiple Positions (US) - A...
Job Description: Sales Specialist - Retail Customer Service and Sales Transform Apple Store visitors into loyal Apple customers. When customers enter the store, Read more
Position Opening at *Apple* - Apple (United...
…customers purchase our products, you're the one who helps them get more out of their new Apple technology. Your day in the Apple Store is filled with a range of Read more
All contents are Copyright 1984-2011 by Xplain Corporation. All rights reserved. Theme designed by Icreon.