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

Capo 3.2 - Slow down and learn to play y...
Capo lets you slow down your favorite songs so you can hear the notes and learn how they are played. With Capo, you can quickly tab out your songs atop a highly-detailed OpenCL-powered spectrogram... Read more
OmniOutliner 4.2.3 - Organize your ideas...
OmniOutliner is a flexible program for creating, collecting, and organizing information. Give your creativity a kick start by using an application that's actually designed to help you think. It's... Read more
pwSafe 4.0.1 - Secure password managemen...
pwSafe provides simple and secure password management across devices and computers. pwSafe uses iCloud to keep your password databases backed-up and synced between Macs and iOS devices. It is... Read more
WALTR 1.5.4 - Drag-and-drop any media fi...
WALTR is designed to make it easy to upload and convert any music or video file to an iPad or iPhone format for native playback. It supports a huge variety of media file types, including MP3, MP4,... Read more
Audio Hijack 3.1 - Record and enhance au...
Audio Hijack (was 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... Read more
PopChar 7.1 - Floating window shows avai...
We're also selling a 5-license family pack for only $25.99! PopChar helps you get the most out of your font collection. With its crystal-clear interface, PopChar X provides a frustration-free way to... Read more
BBEdit 11.1.1 - Powerful text and HTML e...
BBEdit is the leading professional HTML and text editor for the Mac. Specifically crafted in response to the needs of Web authors and software developers, this award-winning product provides a... Read more
Picasa 3.9.139 - Organize, edit, and sha...
Picasa and Picasa Web Albums allows you to organize, edit, and upload your photos to the Web from your computer in quick, simple steps. Arrange your photos into folders and albums and erase their... Read more
Mac DVDRipper Pro 5.0.5 - Copy, backup,...
Mac DVDRipper Pro is the DVD backup solution that lets you protect your DVDs from scratches, save your batteries by reading your movies from your hard disk, manage your collection with just a few... Read more
NetShade 6.2 - Browse privately using an...
This promotion is for NetShade and 1 year of Proxy and VPN services NetShade is an anonymous proxy and VPN app+service for Mac. Unblock your Internet through NetShade's high-speed proxy and VPN... Read more

Block Fortress has a Big New Update for...
Block Fortress is a survival-style game that's as fun as it is blocky. It's also just gotten a rather sizeable update that adds a lot more cool stuff. [Read more] | Read more »
Simple and Surreal Star Base Sim rymdkap...
I really like rymdkapsel. Not just because I'm a sucker for games that are cleverly simple or highly stylisitc, but because it's fun and challenging. Actually it's extremely challenging, which is why I was excited to learn that it's getting a couple... | Read more »
Check out the anticipated Angel Stone in...
Fincon has finally revealed Angel Stone in action in the first ever official gameplay trailer for the anticipated hack and slasher. Angel Stone is set in a post-apocalyptic world in which humanity is in danger of being wiped out by the demonic... | Read more »
Moleskine Timepage is an All-New Calenda...
Moleskine Timepage is a bit of a departure for the notebook manufacturer (since it has little to do with notebooks), but it certainly carries their simple and elegant style quite well. [Read more] | Read more »
Jog on Over and Check Out the New Runtas...
Runtastic has put out a fair number of apps to help you sleep, track excercise, and train various parts of your body. Now it's time for your legs to have their own time in the spotlight with Runtastic Leg Trainer. [Read more] | Read more »
It's Lights Out in the Upcoming Pla...
Ember’s Journey is a stark puzzle platformer with a twist: the entire game is played in darkness. The only light you can see by is the one emanating from your own character. [Read more] | Read more »
MooVee - Your Movies Guru (Entertainmen...
MooVee - Your Movies Guru 1.0 Device: iOS iPhone Category: Entertainment Price: $1.99, Version: 1.0 (iTunes) Description: MooVee helps you effortlessly manage your movies, on your iPhone. | Read more »
Geometry Wars 3: Dimensions (Games)
Geometry Wars 3: Dimensions 1.0.0 Device: iOS Universal Category: Games Price: $4.99, Version: 1.0.0 (iTunes) Description: Enjoy the next chapter in the award-winning Geometry Wars franchise and enjoy stunning, console-quality... | Read more »
CHAOS RINGS Ⅲ (Games)
CHAOS RINGS Ⅲ 1.0.0 Device: iOS Universal Category: Games Price: $19.99, Version: 1.0.0 (iTunes) Description: The newest addition to the popular smartphone RPG series is finally here! ・CHAOS RINGS Overview | Read more »
The Popular Insight Series of Travel Gui...
Getting around in a country when you can't understand the primary language can be tough. Fortunately there are several options available to help wold travellers with the important stuff like giving directions to a cab driver or asking where the... | Read more »

Price Scanner via MacPrices.net

Apple restocks refurbished Mac minis for up t...
The Apple Store has restocked Apple Certified Refurbished 2014 Mac minis, with models available starting at $419. Apple’s one-year warranty is included with each mini, and shipping is free: - 1.4GHz... Read more
13-inch 2.4GHz Retina MacBook Pro (refurbishe...
The Apple Store has 2013 Apple Certified Refurbished 13″ 2.4GHz/128GB Retina MacBook Pros available for $879–$320 off original MSRP. Apple’s one-year warranty is standard, and shipping is free: - 13... Read more
Apple refurbished iPad Air 2s now available f...
The Apple Store is now offering Apple Certified Refurbished iPad Air 2s for up to $140 off the price of new models. Apple’s one-year warranty is included with each model, and shipping is free: -... Read more
MacBook Airs on sale for up to $80 off MSRP
Save up to $80 on the purchase of a new 2015 13″ or 11″ 1.6GHz MacBook Air at the following resellers. Shipping is free with each model: 11" 128GB MSRP $899 11" 256GB... Read more
Free Glide Live Video Messaging App Brings Ne...
Glide, an Israeli startup whose popular live video messenger has attracted more than 15 million users, has released significant updates to its free iOS app. Glide for iOS now gives users more control... Read more
Top Markets Saturation To Slow Global Smartph...
According to a new mobile phone forecast from the International Data Corporation (IDC) Worldwide Quarterly Mobile Phone Tracker, smartphone shipments are expected to grow 11.3% in 2015 — down from 27... Read more
Apple’s Education discount saves up to $300 o...
Purchase a new Mac or iPad at The Apple Store for Education and take up to $300 off MSRP. All teachers, students, and staff of any educational institution qualify for the discount. Shipping is free,... Read more
13-inch 2.5GHz MacBook Pro (refurbished) avai...
The Apple Store has Apple Certified Refurbished 13″ 2.5GHz MacBook Pros available for $829, or $270 off the cost of new models. Apple’s one-year warranty is standard, and shipping is free: - 13″ 2.... Read more
Apple refurbished 2014 13-inch Retina MacBook...
The Apple Store has Apple Certified Refurbished 2014 13″ Retina MacBook Pros available for up to $400 off original MSRP, starting at $979. An Apple one-year warranty is included with each model, and... Read more
What Would the ideal Apple Productivity Platf...
For the past four years I’ve kept a foot in both the Mac and iPad camps respectively. my daily computing hours divided about 50/50 between the two devices with remarkable consistency. However, there’... Read more

Jobs Board

*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
Program Manager, *Apple* Community Support...
**Job Summary** Apple Support Communities ( discussions. apple .com) helps customers get the most from their Apple products and services by providing access to Read more
Senior Data Scientist, *Apple* Retail - Onl...
**Job Summary** Apple Retail - Online sells Apple products to customers around the world. In addition to selling Apple products with unique services such as iPad Read more
*Apple* Solutions Consultant - Retail Sales...
**Job Summary** As an Apple Solutions Consultant (ASC) you are the link between our customers and our products. Your role is to drive the Apple business in a retail Read more
*Apple* Watch SW Application Project Manager...
**Job Summary** The Apple Watch software team is looking for an Application Engineering Project Manager to work on new projects for Apple . The successful candidate Read more
All contents are Copyright 1984-2011 by Xplain Corporation. All rights reserved. Theme designed by Icreon.