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
$118.48
Apple Inc.
+2.01
MSFT
$47.76
Microsoft Corpora
-0.22
GOOG
$538.53
Google Inc.
+1.03

MacTech Search:
Community Search:

Software Updates via MacUpdate

Carbon Copy Cloner 4.0.3 - Easy-to-use b...
Carbon Copy Cloner backups are better than ordinary backups. Suppose the unthinkable happens while you're under deadline to finish a project: your Mac is unresponsive and all you hear is an ominous,... Read more
ForeverSave 2.1.3 - Universal auto-save...
ForeverSave auto-saves all documents you're working on while simultaneously doing backup versioning in the background. Lost data can be quickly restored at any time. Losing data, caused by... Read more
Voila 3.8.1 - Capture, annotate, organiz...
Voila is a screen-capture, recording, and annotation tool that is a full-featured replacement for Mac's screen-capture and screen-recording capabilities. It has a large and robust set of editing,... Read more
SyncTwoFolders 2.0.6 - Syncs two user-sp...
SyncTwoFolders simply synchronizes two folders. It supports synchronization across mounted network drives and it is a possibility to run a simulation showing in a log what will be done. Please visit... Read more
Duplicate Annihilator 5.1.1 - Find and d...
Duplicate Annihilator takes on the time-consuming task of comparing the images in your iPhoto library using effective algorithms to make sure that no duplicate escapes. Duplicate Annihilator detects... Read more
Cobook 3.0.7 - Intelligent address book....
Cobook Contacts is an intuitive, engaging address book. Solve the problem of contact management with Cobook Contacts and its simple interface and powerful syncing and integration possibilities.... Read more
StatsBar 1.9 - Monitor system processes...
StatsBar gives you a comprehensive and detailed analysis of the following areas of your Mac: CPU usage Memory usage Disk usage Network and bandwidth usage Battery power and health (MacBooks only)... Read more
Cyberduck 4.6 - 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
Maya 2015 - Professional 3D modeling and...
Maya is an award-winning software and powerful, integrated 3D modeling, animation, visual effects, and rendering solution. Because Maya is based on an open architecture, all your work can be scripted... Read more
Evernote 6.0.1 - Create searchable notes...
Evernote allows you to easily capture information in any environment using whatever device or platform you find most convenient, and makes this information accessible and searchable at anytime, from... Read more

Latest Forum Discussions

See All

RuPaul’s Drag Race: Dragopolis 2.0 is C...
RuPaul’s Drag Race: Dragopolis 2.0 is Coming to iOS December 4th Posted by Jessica Fisher on November 24th, 2014 [ permalink ] So Much Drama | Read more »
Crimson Keyboard (Utilities)
Crimson Keyboard 1.0 Device: iOS iPhone Category: Utilities Price: $1.99, Version: 1.0 (iTunes) Description: Introducing a faster way to type. Crimson Keyboard adapts to your writing style and provides smart, personal and contextual... | Read more »
The Sandbox EDU Review
The Sandbox EDU Review By Nadia Oxford on November 24th, 2014 Our Rating: :: COME PLAY IN THE SANDBOX AGAINUniversal App - Designed for iPhone and iPad Like its predecessor, The Sandbox EDU offers lots for players to see, do, and... | Read more »
Taichi Panda Hits iOS in December
Taichi Panda Hits iOS in December Posted by Jessica Fisher on November 24th, 2014 [ permalink ] Snail Games has released the first official game play trailer for  | Read more »
Five Apps to Make Your Thanksgiving Plan...
Thanksgiving is nearly upon us! You know what that means? Eating too much turkey, watching the Big Game, and spending time with family (whether you like it or not). Oh, and that scary Black Friday thing, but we won’t talk about that here. For those... | Read more »
Kingdom Rush Origins HD Review
Kingdom Rush Origins HD Review By Jennifer Allen on November 24th, 2014 Our Rating: :: JUST AS GOOD AS BEFOREiPad Only App - Designed for the iPad It’s more of the same again, but that’s really no bad thing at all.   | Read more »
Skylanders, Show Off How You Fight Kaos...
Skylanders, Show Off How You Fight Kaos to Win Cool Prizes Posted by Jessica Fisher on November 24th, 2014 [ permalink ] iPad Only App - Designed for the iPad | Read more »
Mark of the Dragon – Tips, Tricks, and S...
Calling All Dragon Riders: | Read more »
Playdek has Annouced a Delicious Thanksg...
Playdek has Annouced a Delicious Thanksgiving Sale Posted by Jessica Fisher on November 24th, 2014 [ permalink ] Playdek, makers of | Read more »
Pair Solitaire Review
Pair Solitaire Review By Jennifer Allen on November 24th, 2014 Our Rating: :: ADDICTIVE. SO ADDICTIVEUniversal App - Designed for iPhone and iPad Welcome to your new ‘five more minutes, oh no, why is it dark outside’ addiction.   | Read more »

Price Scanner via MacPrices.net

Jumptuit Launches One-Tap Windows 8.1 iTunes...
Jumptuit has launched Windows 8.1 support for One-Tap iTunes Sync. with which Windows 8.1 users can now easily sync their iTunes libraries with Microsoft OneDrive. Jumptuit provides easy access from... Read more
CEA Study Finds More People Recycling Electro...
A new study by the Consumer Electronics Association (CEA) finds that electronics recycling receives the continued and growing support of consumers. According to the CEA,s Recycling and Reuse Study,... Read more
15″ 2.2GHz Retina MacBook Pro on sale for $17...
 B&H Photo has the 2014 15″ 2.2GHz Retina MacBook Pro on sale today for $1749. Shipping is free, and B&H charges NY sales tax only. B&H will also include free copies of Parallels Desktop... Read more
27-inch 3.5GHz 5K iMac in stock today and on...
 B&H Photo has the new 27″ 3.5GHz 5K iMac in stock today and on sale for $2299 including free shipping plus NY sales tax only. Their price is $200 off MSRP, and it’s the lowest price available... Read more
21-inch 1.4GHz iMac on sale for $979, save $1...
B&H Photo has the new 21″ 1.4GHz iMac on sale for $979.99 including free shipping plus NY sales tax only. Their price is $120 off MSRP. B&H will also include free copies of Parallels Desktop... Read more
13-inch 1.4GHz/256GB MacBook Air on sale for...
B&H Photo has lowered their price on the 13″ 1.4GHz/256GB MacBook Air to $1059.99 including free shipping plus NY sales tax only. Their price is $140 off MSRP, and it’s the lowest price for this... Read more
Save up to $400 with Apple refurbished 2014 1...
The Apple Store has restocked Apple Certified Refurbished 2014 15″ Retina MacBook Pros for up to $400 off the cost of new models. An Apple one-year warranty is included with each model, and shipping... Read more
New 13-inch 1.4GHz MacBook Air on sale for $8...
 Adorama has the 2014 13″ 1.4GHz/128GB MacBook Air on sale for $899.99 including free shipping plus NY & NJ tax only. Their price is $100 off MSRP. B&H Photo has the 13″ 1.4GHz/128GB MacBook... Read more
Apple Expected to Reverse Nine-Month Tablet S...
Apple and Samsung combined accounted for 62 percent of the nearly 36 million branded tablets shipped in 3Q 2014, according to early vendor shipment share estimates from market intelligence firm ABI... Read more
Stratos: 30 Percent of US Smartphone Owners t...
Stratos, Inc., creator of the Bluetooth Connected Card Platform, has announced results from its 2014 Holiday Mobile Payments Survey. The consumer survey found that nearly one out of three (30 percent... Read more

Jobs Board

*Apple* Retail - Multiple Positions (US) - A...
Sales Specialist - Retail Customer Service and Sales Transform Apple Store visitors into loyal Apple customers. When customers enter the store, you're also the 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
*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
*Apple* Solutions Consultant (ASC)- Retail S...
**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, *Apple* Financial Services...
**Job Summary** Apple Financial Services (AFS) offers consumers, businesses and educational institutions ways to finance Apple purchases. We work with national and Read more
All contents are Copyright 1984-2011 by Xplain Corporation. All rights reserved. Theme designed by Icreon.