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...

 

Community Search:
MacTech Search:

Software Updates via MacUpdate

Microsoft Remote Desktop 8.0.34 - Connec...
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
Data Rescue 4.2.3 - Powerful hard drive...
Use Data Rescue to recover: crashed, corrupted or non-mounting hard drive deleted, damaged, or lost files reformatted or erased hard drive One powerful new feature found in Data Rescue 4 is... Read more
Viber 6.2.0 - Send messages and make cal...
Viber lets you send free messages and make free calls to other Viber users, on any device and network, in any country! Viber syncs your contacts, messages and call history with your mobile device, so... Read more
Lyn 1.7.2 - Lightweight image browser an...
Lyn is a fast, lightweight image browser and viewer designed for photographers, graphic artists, and Web designers. Featuring an extremely versatile and aesthetically pleasing interface, it delivers... Read more
Lyn 1.7.2 - Lightweight image browser an...
Lyn is a fast, lightweight image browser and viewer designed for photographers, graphic artists, and Web designers. Featuring an extremely versatile and aesthetically pleasing interface, it delivers... Read more
Tunnelblick 3.6.7beta02 - GUI for OpenVP...
Tunnelblick is a free, open source graphic user interface for OpenVPN on OS X. It provides easy control of OpenVPN client and/or server connections. It comes as a ready-to-use application with all... Read more
jAlbum Pro 13.4 - Organize your digital...
jAlbum Pro has all the features you love in jAlbum, but comes with a commercial license. You can create gorgeous custom photo galleries for the Web without writing a line of code! Beginner-friendly... Read more
calibre 2.65.1 - Complete e-book library...
Calibre is a complete e-book library manager. Organize your collection, convert your books to multiple formats, and sync with all of your devices. Let Calibre be your multi-tasking digital librarian... Read more
jAlbum 13.4 - Create custom photo galler...
With jAlbum, you can create gorgeous custom photo galleries for the Web without writing a line of code! Beginner-friendly, with pro results - Simply drag and drop photos into groups, choose a design... Read more
Backblaze 4.2.0.966 - Online backup serv...
Backblaze is an online backup service designed from the ground-up for the Mac. With unlimited storage available for $5 per month, as well as a free 15-day trial, peace of mind is within reach with... Read more

5 mobile games that let you explore spac...
No Man's Sky hasn't exactly turned out to be everything it was promised. Though its core concept of exploring an unimaginably vast universe of different planets is an intriguing one, the execution has left many PS4 and PC gamers feeling like they... | Read more »
Mummy madness in new action game Tomb He...
Hot on the tail of Bump Hero, ZPlay is giving gamers another reason to get screen bashing with a brand new release. Tomb Heroes is a challenging action game in which you battle enemies in various tombs around the world. You can select from nine... | Read more »
Siralim 2 (RPG / Roguelike) (Games)
Siralim 2 (RPG / Roguelike) 1.0 Device: iOS Universal Category: Games Price: $4.99, Version: 1.0 (iTunes) Description: Siralim 2 is an old-school monster catching RPG. Summon and customize hundreds of creatures to fight for you as... | Read more »
Clean Text (Productivity)
Clean Text 1.0 Device: iOS Universal Category: Productivity Price: $3.99, Version: 1.0 (iTunes) Description: | Read more »
Gemini - A Journey of Two Stars (Games)
Gemini - A Journey of Two Stars 1.0.1 Device: iOS Universal Category: Games Price: $2.99, Version: 1.0.1 (iTunes) Description: *** SPECIAL LAUNCH SALE: $2.99 (25% off) *** "A mesmerizing and unexpectedly emotional journey." -- Los... | Read more »
How to get four NFL superstars for your...
Even though you're probably well on your way to building a top notch squad for the new season in Madden NFL Mobile, let's say you could beef it up by adding Rob Gronkowski, Antonio Brown, Von Miller, and Todd Gurley to your roster. That's... | Read more »
Cartoon Network Superstar Soccer: Goal!!...
Cartoon Network Superstar Soccer: Goal!!! – Multiplayer Sports Game Starring Your Favorite Characters 1.0 Device: iOS Universal Category: Games Price: $2.99, Version: 1.0 (iTunes) Description: Become a soccer superstar with your... | Read more »
NFL Huddle: What's new in Topps NFL...
Can you smell that? It's the scent of pigskin in the air, which either means that cliches be damned, pigs are flying in your neck of the woods, or the new NFL season is right around the corner. [Read more] | Read more »
FarmVille: Tropic Escape tips, tricks, a...
Maybe farming is passé in mobile games now. Ah, but farming -- and doing a lot of a other things too -- in an island paradise might be a little different. At least you can work on your tan and sip some pina coladas while tending to your crops. [... | Read more »
Become the King of Avalon in FunPlus’ la...
King Arthur is dead. Considering the legend dates back to the 5th century, it would be surprising if he wasn’t. But in the context of real-time MMO game King of Avalon: Dragon Warfare, Arthur’s death plunges the kingdom into chaos. Evil sorceress... | Read more »

Price Scanner via MacPrices.net

9-inch 32GB iPad Pros on sale for $70 off MSR...
B&H Photo has 9″ 32GB WiFi Apple iPad Pros on sale for $70 off MSRP, each including free shipping. B&H charges sales tax in NY only: - 9″ Space Gray 32GB WiFi iPad Pro: $529 $70 off MSRP - 9... Read more
Mac minis on sale for up to $140 off MSRP
Adorama has Mac minis on sale for up to $100 off MSRP including free shipping plus NY & NJ sales tax only: - 1.4GHz Mac mini: $449 $50 off MSRP - 2.6GHz Mac mini: $649 $50 off MSRP Amazon has the... Read more
Back To School with OtterBox Essentials
Back to school means back to an environment that is tough on tech. OtterBox has the back to school essentials you need to keep tech safe from drops, bumps, scratches and hallway havoc. Check out the... Read more
VRS Design Releases New iPhone 7 Plus Case Li...
With a device as large and costly as the iPhone 7 Plus, it is primal instinct to protect it from potential damage. According to a study by SquareTrade in 2012, iPhone damages cost Americans roughly $... Read more
MacBook Airs on sale for up to $101 off MSRP
Amazon has 11″ and 13″ MacBook Airs on sale for up to $101 off MSRP for a limited time. Shipping is free: - 11″ 1.6GHz/128GB MacBook Air (model MJVM2LL/A): $798 $101 off MSRP - 11″ 1.6GHz/256GB... Read more
Apple certified refurbished iPad mini 4s avai...
Apple has certified refurbished iPad mini 4s now available for up to $120 off the cost of new models. An Apple one-year warranty is included with each iPad, and shipping is free. The following models... Read more
Apple price trackers, updated continuously
Scan our Apple Price Trackers for the latest information on sales, bundles, and availability on systems from Apple’s authorized internet/catalog resellers. We update the trackers continuously: - 15″... Read more
Global Tablet Shipments Projected to Increase...
Digitimes’ Jim Hsiao reports that global tablet shipments will increase by 16.3 percent sequentially to reach nearly 47 million units in 2016′s third quarter, but that volume will still be down over... Read more
Apple’s 2016 Back to School promotion: Free B...
Purchase a new Mac or iPad using Apple’s Education Store and take up to $300 off MSRP. All teachers, students, and staff of any educational institution qualify for the discount. Shipping is free, and... Read more
Apple refurbished iPad Air 2s available start...
Apple has Certified Refurbished iPad Air 2 available starting at $339. Apple’s one-year warranty is included with each model, and shipping is free: - 128GB Wi-Fi iPad Air 2: $499 - 64GB Wi-Fi iPad... Read more

Jobs Board

*Apple* Solutions Consultant - Apple (United...
Apple Solutions ConsultantJob Number: 51218534Pleasant Hill, California, United StatesPosted: Aug. 18, 2016Weekly Hours: 40.00Job SummaryAs an Apple Solutions Read more
*Apple* Solutions Consultant - Apple (United...
# Apple Solutions Consultant Job Number: 51443201 Mishawaka, Indiana, United States Posted: Aug. 25, 2016 Weekly Hours: 40.00 **Job Summary** As an Apple Read more
*Apple* Solutions Consultant - Apple (United...
# Apple Solutions Consultant Job Number: 51218354 Fredericksburg, Virginia, United States Posted: Aug. 18, 2016 Weekly Hours: 40.00 **Job Summary** As an Apple Read more
*Apple* Retail - Multiple Positions Birmingh...
Job Description: Sales Specialist - Retail Customer Service and Sales Transform Apple Store visitors into loyal Apple customers. When customers enter the store, Read more
SW Engineer *Apple* TV - Apple Inc. (United...
The Apple TV team is looking for excellent software engineers with experience in hardware, media management, media playback, content delivery and a passion for Read more
All contents are Copyright 1984-2011 by Xplain Corporation. All rights reserved. Theme designed by Icreon.