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
$97.03
Apple Inc.
-0.16
MSFT
$44.40
Microsoft Corpora
-0.47
GOOG
$593.35
Google Inc.
-2.63

MacTech Search:
Community Search:

Software Updates via MacUpdate

Audio Hijack Pro 2.11.0 - Record and enh...
Audio Hijack Pro drastically changes the way you use audio on your computer, giving you the freedom to listen to audio when you want and how you want. Record and enhance any audio with Audio Hijack... Read more
Intermission 1.1.1 - Pause and rewind li...
Intermission allows you to pause and rewind live audio from any application on your Mac. Intermission will buffer up to 3 hours of audio, allowing users to skip through any assortment of audio... Read more
Airfoil 4.8.7 - Send audio from any app...
Airfoil allows you to send any audio to AirPort Express units, Apple TVs, and even other Macs and PCs, all in sync! It's your audio - everywhere. With Airfoil you can take audio from any... Read more
Microsoft Remote Desktop 8.0.8 - Connect...
With Microsoft Remote Desktop, you can connect to a remote PC and your work resources from almost anywhere. Experience the power of Windows with RemoteFX in a Remote Desktop client designed to help... Read more
xACT 2.30 - Audio compression toolkit. (...
xACT stands for X Aaudio Compression Toolkit, an application that encodes and decodes FLAC, SHN, Monkey’s Audio, TTA, Wavpack, and Apple Lossless files. It also can encode these formats to MP3, AAC... Read more
Firefox 31.0 - Fast, safe Web browser. (...
Firefox for Mac offers a fast, safe Web browsing experience. Browse quickly, securely, and effortlessly. With its industry-leading features, Firefox is the choice of Web development professionals... Read more
Little Snitch 3.3.3 - Alerts you to outg...
Little Snitch gives you control over your private outgoing data. Track background activityAs soon as your computer connects to the Internet, applications often have permission to send any... Read more
Thunderbird 31.0 - Email client from Moz...
As of July 2012, Thunderbird has transitioned to a new governance model, with new features being developed by the broader free software and open source community, and security fixes and improvements... Read more
Together 3.2 - Store and organize all of...
Together helps you organize your Mac, giving you the ability to store, edit and preview your files in a single clean, uncluttered interface. Smart storage. With simple drag-and-drop functionality,... Read more
Cyberduck 4.5 - FTP and SFTP browser. (F...
Cyberduck is a robust FTP/FTP-TLS/SFTP browser for the Mac whose lack of visual clutter and cleverly intuitive features make it easy to use. Support for external editors and system technologies such... Read more

Latest Forum Discussions

See All

THE KING OF FIGHTERS '98 (Games)
THE KING OF FIGHTERS '98 1.0 Device: iOS Universal Category: Games Price: $3.99, Version: 1.0 (iTunes) Description: Series’ masterpiece “KOF ’98” finally joins the battle on iPhone! FEATURES:■ The best game balance in the “KOF”... | Read more »
LEX Goes Free For One Day In Honor of Ne...
LEX Goes Free For One Day In Honor of New Update Posted by Jennifer Allen on July 24th, 2014 [ permalink ] Universal App - Designed for iPhone and iPad | Read more »
Thomas Was Alone Goes Universal, Slashes...
Thomas Was Alone Goes Universal, Slashes Price to $3.99 Posted by Ellis Spice on July 24th, 2014 [ permalink ] Universal App - Designed for iPhone and iPad | Read more »
Meerkatz Challenge Review
Meerkatz Challenge Review By Jennifer Allen on July 24th, 2014 Our Rating: :: FONDLY PUZZLINGUniversal App - Designed for iPhone and iPad Cute and challenging, Meerkatz Challenge is a fun puzzle game, particularly for fans of... | Read more »
Book Your Appointment with F.E.A.R. this...
Book Your Appointment with F.E.A.R. | Read more »
It Came From Canada: Epic Skater
For all the hate that it gets for being a pastime for slackers, skateboarding really does require a lot of skill. All those flips and spins take real athleticism, and there’s all the jargon to memorize. Fortunately for us less extreme individuals,... | Read more »
Cultures Review
Cultures Review By Jennifer Allen on July 24th, 2014 Our Rating: :: SLOW-PACED EMPIRE BUILDINGiPad Only App - Designed for the iPad Cute it might seem, but Cultures is a bit too slow paced when it comes to those pesky timers to... | Read more »
More Paintings Have Been Added to Paint...
More Paintings Have Been Added to Paint it Back! Posted by Jessica Fisher on July 24th, 2014 [ permalink ] Universal App - Designed for iPhone and iPad | Read more »
The Order of Souls Review
The Order of Souls Review By Campbell Bird on July 24th, 2014 Our Rating: :: STORY GRINDUniversal App - Designed for iPhone and iPad The Order of Souls is a free-to-play, turn-based RPG with a genre-mixing art style, interesting... | Read more »
Revolution 60 Review
Revolution 60 Review By Jordan Minor on July 24th, 2014 Our Rating: :: LASS EFFECTUniversal App - Designed for iPhone and iPad Revolution 60 is a bold, cinematic action game with ambition to spare.   | Read more »

Price Scanner via MacPrices.net

Mac minis on sale for $100 off MSRP, starting...
Best Buy has Mac minis on sale for $100 off MSRP. Choose free shipping or free instant local store pickup. Prices are for online orders only, in-store prices may vary: 2.5GHz Mac mini: $499.99 2.3GHz... Read more
Global Tablet Market Grows 11% in Q2/14 Notwi...
Worldwide tablet sales grew 11.0 percent year over year in the second quarter of 2014, with shipments reaching 49.3 million units according to preliminary data from the International Data Corporation... Read more
New iPhone 6 Models to Have Staggered Release...
Digitimes’ Cage Chao and Steve Shen report that according to unnamed sources in Apple’s upstream iPhone supply chain, the new 5.5-inch iPhone will be released several months later than the new 4.7-... Read more
New iOS App Helps People Feel Good About thei...
Mobile shoppers looking for big savings at their favorite stores can turn to the Goodshop app, a new iOS app with the latest coupons and deals at more than 5,000 online stores. In addition to being a... Read more
Save on 5th generation refurbished iPod touch...
The Apple Store has Apple Certified Refurbished 5th generation iPod touches available starting at $149. Apple’s one-year warranty is included with each model, and shipping is free. Many, but not all... Read more
What Should Apple’s Next MacBook Priority Be;...
Stabley Times’ Phil Moore says that after expanding its iMac lineup with a new low end model, Apple’s next Mac hardware decision will be how it wants to approach expanding its MacBook lineup as well... Read more
ArtRage For iPhone Painting App Free During C...
ArtRage for iPhone is currently being offered for free (regularly $1.99) during Comic-Con San Diego #SDCC, July 24-27, in celebration of the upcoming ArtRage 4.5 and other 64-bit versions of the... Read more
With The Apple/IBM Alliance, Is The iPad Now...
Almost since the iPad was rolled out in 2010, and especially after Apple made a 128 GB storage configuration available in 2012, there’s been debate over whether the iPad is a serious tool for... Read more
MacBook Airs on sale starting at $799, free s...
B&H Photo has the new 2014 MacBook Airs on sale for up to $100 off MSRP for a limited time. Shipping is free, and B&H charges NY sales tax only. They also include free copies of Parallels... Read more
Apple 27″ Thunderbolt Display (refurbished) a...
The Apple Store has Apple Certified Refurbished 27″ Thunderbolt Displays available for $799 including free shipping. That’s $200 off the cost of new models. Read more

Jobs Board

*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
Sr. Project Manager for *Apple* Campus 2 -...
…the design and construction of one building or building components of the New Apple Campus located in Cupertino, CA. They will provide project management oversight for Read more
WW Sales Program Manager, *Apple* Online St...
**Job Summary** Imagine what you could do here. At Apple , great ideas have a way of becoming great products, services, and customer experiences very quickly. Bring 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
All contents are Copyright 1984-2011 by Xplain Corporation. All rights reserved. Theme designed by Icreon.