Constructor in applet?
hi.....
Can we do provide constructor in an applet for initialization or can applet support constructor?
regards.
What?
Applets need to have a no-arg constructor, and they also have an init() method and a start() method. There's some documentation online, probably within the tutorials on java.sun.com as well, that describe the applet lifecycle. You should read it.
Similar Messages
-
Why applets are not having constructors?
hi,
could anyone please explain ,why do we need to use init() method instead of constructor to initialize the applets.why applets are not having constructors?.
thanks in advance
SanthoshSure u CAN have constructors for applets. Event though you havnt wrote it, its always there... There cant be a class without a constructor......
The point is that its a standard that the applets init will be caled by the browser the first time.....but still you can have a constructor. -
Sorry if i sound foolish how to run an applet through a java application
I am into java from last one month ank keep on exploring it in the want to
recently i created a application cum applet in the same class like
applet is doing its own task and there is a main method in the code
that does entirly different task lets assume displaying *'s on the dos prompt the program is getting complied and belive it its running as desired
but the only problem that i m facing if i use appletviewer Myclass.java
only the appletprog is displayed
and if i run java Myclass than only dos task is done
may be it is sounding foolish for most of you but if i can get a way
which will help me in excecuting only one of it and both of them run succesfully
it tryied different ways to do it but was not succesful
please do not get irreated if its bizzered but if you really have a solution for it .i will appreciate it
thanking youYes you can run an Applet from an application. The magic bit is providing an AppletContext and AppletStub!
Here's how you start it:
wpa = new WayPointsApplet(this);
new AppletWrapper(wpa, 380, 320);Here's the class definition: (includes code for my application that can be ignored.
// Define a wrapper class for the applet
class AppletWrapper extends Frame implements AppletStub, AppletContext {
Applet applet;
// Constructor
AppletWrapper(Applet a, int x, int y) {
applet = a;
setTitle(a.getClass().getName());
setSize(x, y);
Dimension ss = Toolkit.getDefaultToolkit().getScreenSize();
setLocation((ss.width-x)/2, (ss.height-y)/2);
add(a, "Center");
a.setStub(this);
// Trap window closing
addWindowListener(new WindowAdapter() {
public void windowClosing(WindowEvent we) {
// Test if Write left undone before exiting???
if(WayPoints.wpa != null) {
if(!WayPoints.wpa.okToExit())
return; // Ignore
applet.stop();
applet.destroy();
if(WayPoints.debug || WayPointDefs.plot_debug) {
SaveStdOutput.stop();
System.exit(0); // EXIT Program
}); // end WindowListener
a.init();
show();
a.start();
} // end constructor
// AppletStub methods
public boolean isActive() { return true; }
public URL getDocumentBase() { return null; }
public URL getCodeBase() {
return WayPoints.currDir;
public String getParameter(String name) {
if (name.equalsIgnoreCase("DEBUG")) {
if (WayPoints.debug)
return "YES";
else
return "NO";
if(name.equals("PLOTDEBUG"))
return (WayPointDefs.plot_debug ? "YES" : "NO");
if (name.equalsIgnoreCase("SERVER"))
return "NO";
return "";
public AppletContext getAppletContext() { return this; }
public void appletResize(int width, int height) {}
// AppletContext methods
public AudioClip getAudioClip(URL url) { return null; }
public Image getImage(URL url) { return null; }
public Applet getApplet(String name) { return null; }
public Enumeration getApplets() { return null; }
public void showDocument(URL url) {}
public void showDocument(URL url, String target) {}
public void showStatus(String status) {}
} // end class AppletWrapper -
how can I open a Dialog in an Applet,
all Dialog constructors requires a JFrame or Dialog owner,
is there a constructor for Applet?U can get a parent frame "handle" like this:
Component frame = this;
while(!(frame instanceof Frame))
frame = frame.getParent(); -
Revision: 20505
Revision: 20505
Author: [email protected]
Date: 2011-03-01 07:31:55 -0800 (Tue, 01 Mar 2011)
Log Message:
Bug: Watson #2818669 - AbstractAmfInput uses System.getProperty in Constructor leading to AccessControlException when using in Applet
QA: Yes
Doc: No
Checkintests: Didn't run - the change was to wrap the System.getProperty in a try/catch that would have caused the SecurityException, so no real functionality change that could affect the check-in tests.
Modified Paths:
blazeds/trunk/modules/core/src/flex/messaging/io/amf/AbstractAmfInput.java -
Exception 6A80 while setting Triple DES key inside the applet constructor
In the applet definition part, I am having these definition:
public static final byte DEFAULT_PERSO_KEY_SET_REFERENCE = (byte) 0x81;
public static final byte[] DEFAULT_PERSO_KEY_SET_ENC = {
(byte) 0x52, (byte) 0x57, (byte) 0x4d, (byte) 0x41,
(byte) 0x43, (byte) 0x45, (byte) 0x43, (byte) 0x48,
(byte) 0x41, (byte) 0x4e, (byte) 0x54, (byte) 0x49,
(byte) 0x4c, (byte) 0x4c, (byte) 0x4f, (byte) 0x4e
public static final byte[] DEFAULT_PERSO_KEY_SET_MAC = {
(byte) 0x52, (byte) 0x57, (byte) 0x45, (byte) 0x4e,
(byte) 0x43, (byte) 0x45, (byte) 0x43, (byte) 0x48,
(byte) 0x41, (byte) 0x4e, (byte) 0x54, (byte) 0x49,
(byte) 0x4c, (byte) 0x4c, (byte) 0x4f, (byte) 0x4e
public Key keyEnc;
public Key keyMac;In the applet constructor I am having these lines of code:
keyEnc = (DESKey) KeyBuilder.buildKey(KeyBuilder.TYPE_DES, KeyBuilder.LENGTH_DES3_2KEY,
false);
keyMac = (DESKey) KeyBuilder.buildKey(KeyBuilder.TYPE_DES, KeyBuilder.LENGTH_DES3_2KEY,
false);
((DESKey) keyMac).setKey(DEFAULT_PERSO_KEY_SET_MAC, (short) 0);
((DESKey) keyEnc).setKey(DEFAULT_PERSO_KEY_SET_ENC, (short) 0);On line when the MAC is setting, the next exception is thrown:
Status: Wrong data
jcshell: Error code: 6a80 (Wrong data)
jcshell: Wrong response APDU: 6A80
Unexpected error; aborting execution>
Status: Wrong data
jcshell: Error code: 6a80 (Wrong data)
jcshell: Wrong response APDU: 6A80
Unexpected error; aborting execution
>
usually unhandled exceptions do not look like this. If you catch the exception you can try to specify the reason. May be the problem in parity bits of des keys, though this error is not listed in possible exceptions of setKey method. -
ERROR:The applet Tennisball does not have a public constructor Tennisball()
hi all...sorry...i encountered this java error msg with the following code.....n the error msg tat was generated is that i do not have a public constructor which i already have...can some1 please enlighten me..??
import java.applet.*;
import java.awt.*;
public class Tennisball
double x, y, oldx, oldy, xinc, yinc, v=2.0;
int i,e,west,north,east,south,ry,rs,score,rx;
int choice, zone;
AudioClip ballout;
boolean running,toggle,enough;
Color ballcolor;
Tennis t;
Color bgColor = Color.black;
public Tennisball(int w, int n, int e, int s, AudioClip bo)
west=w;
east=e;
south=s;
north=n;
ballout = bo;
//this.t = t;
xinc=1.7*v;
yinc=0.7*v;
public void getRacketPosition(int racket_y)
ry=racket_y;
rs=ry;
public void newBall()
ballcolor=Color.yellow;
x=20;
y=(int)(Math.random()*100+50);
int angle=(int)(Math.random()*8+1);
if(angle==1)yinc=-0.7*v;
if(angle==2)yinc=-0.5*v;
if(angle==3)yinc=-0.4*v;
if(angle==4)yinc=-0.3*v;
if(angle==5)yinc=0.3*v;
if(angle==6)yinc=0.4*v;
if(angle==7)yinc=0.5*v;
if(angle==8)yinc=0.7*v;
toggle=false;
running=true;
enough=false;
e=0;
public void move()
if(running)
if(!toggle)
oldx=x;
oldy=y;
x+=xinc*v;
y+=yinc*v;
if(x<west && xinc<0)
int angle=(int)(Math.random()*8+1);
if(angle==1)yinc=-0.7*v;
if(angle==2)yinc=-0.5*v;
if(angle==3)yinc=-0.4*v;
if(angle==4)yinc=-0.3*v;
if(angle==5)yinc=0.3*v;
if(angle==6)yinc=0.4*v;
if(angle==7)yinc=0.5*v;
if(angle==8)yinc=0.7*v;
xinc=-xinc;
t.playClick();
else if(x>east-10)
x=east-10;
toggle=true;
running=false;
score++;
t.playBallout();
else if(y<north || y>south)
if(y<north&&yinc<0)
yinc=-yinc;
if(y>south&&yinc>0)
yinc=-yinc;
t.playClick();
else if(x>425 && xinc>0 && y>ry && y<rs+25)
if(y<ry+3)zone=1;
else if(y>=ry+3&&y<ry+6)zone=2;
else if(y>=ry+6&&y<ry+9)zone=3;
else if(y>=ry+9&&y<ry+12)zone=4;
else if(y>=ry+12&&y<ry+15)zone=5;
else if(y>=ry+15&&y<ry+18)zone=6;
else if(y>=ry+18&&y<ry+21)zone=7;
else if(y>=ry+21)zone=8;
if(zone==1)yinc=-0.7*v;
if(zone==2)yinc=-0.5*v;
if(zone==3)yinc=-0.4*v;
if(zone==4)yinc=-0.3*v;
if(zone==5)yinc=0.3*v;
if(zone==6)yinc=0.4*v;
if(zone==7)yinc=0.5*v;
if(zone==8)yinc=0.7*v;
xinc=-xinc;
t.playClick();
public void toggle()
int i=t.j;
if(!enough)
if(i>-1&&i<11)ballcolor=Color.yellow;
if(i>10&&i<20){ballcolor=bgColor;e++;}
if (e>35){ballcolor=bgColor;enough=true;}
public void paint(Graphics g)
if(toggle)toggle();
g.setColor(ballcolor);
g.fillOval((int)x,(int)y,10,10);
}I thought I should point out a few things
The rule is that every class should have a no
argument constructor that you need to specify
explicitly if you have overloaded the default one.
One of the reaons for that is the following:This is not true, there are many classes that do not have a no argument constructor (For example Integer). Integer is a perfect example of why you would not want a no argument constructor, having an Integer with no value is pointless (theres nothing you can do with it).
public class A {
private final int a ;
public A(int b) {
this.a = b ;
}Now you realize that the variable
n
is getting initialized in the constructor. I see no variable n in the constructor but I take it you mean a
Now if you
refer to
n
somewhere else in you code you get a compile error because
n
might not have been initialized.This is not true, only local variables can cause a
variable (a variable) might not have been initialized
this is because all member fields are initialised with their default valuse. For example all pointers are intitialised to null, ints are intitialised to 0, booleans to false and so on.
>
So you need this:
public class A {
private final int a ;
public A(int b) {
this.a = b ;
public A() {
this(0) ; /* Calls the above constructor with some
default parameter. */
/* You can add some more code below but not above
this(0) */
Of course you know you are never calling the default
constructor but it's still there so you need to
ensure that the variables get initialized if some one
calls it!
As above classes can have no argument constructors
Just add this to your code for example:
public Tennisball() {
this(0, 0, 0, 0, null) ;
} Hope that helped you out!
Thanks,
Nikolas.
PS any duke dollars would be much appreciated as i'm
very poor at the moment :-)I dont mean to be offensive just thought I should clarify these points
Michael -
The applet FtpExample does not have a public constructor FtpExample()
Hi
Get this from my Jbuilder, but I got an constructor. What's the problem ?
import ftp.*;
import java.io.*;
import java.applet.*;
class FtpExample implements FtpObserver, Runnable
Thread thread;
FtpBean ftp;
long num_of_bytes = 0;
public FtpExample()
// Create a new FtpBean object.
ftp = new FtpBean();
try {
jbInit();
} catch (Exception ex) {
ex.printStackTrace();
// Connect to a ftp server.
public void connect()
try
ftp.ftpConnect("xxxxxxxxxxxx", "xxxxxxx", "xxxxxxx");
} catch(Exception e)
System.out.println(e);
and more...
.I thought I should point out a few things
The rule is that every class should have a no
argument constructor that you need to specify
explicitly if you have overloaded the default one.
One of the reaons for that is the following:This is not true, there are many classes that do not have a no argument constructor (For example Integer). Integer is a perfect example of why you would not want a no argument constructor, having an Integer with no value is pointless (theres nothing you can do with it).
public class A {
private final int a ;
public A(int b) {
this.a = b ;
}Now you realize that the variable
n
is getting initialized in the constructor. I see no variable n in the constructor but I take it you mean a
Now if you
refer to
n
somewhere else in you code you get a compile error because
n
might not have been initialized.This is not true, only local variables can cause a
variable (a variable) might not have been initialized
this is because all member fields are initialised with their default valuse. For example all pointers are intitialised to null, ints are intitialised to 0, booleans to false and so on.
>
So you need this:
public class A {
private final int a ;
public A(int b) {
this.a = b ;
public A() {
this(0) ; /* Calls the above constructor with some
default parameter. */
/* You can add some more code below but not above
this(0) */
Of course you know you are never calling the default
constructor but it's still there so you need to
ensure that the variables get initialized if some one
calls it!
As above classes can have no argument constructors
Just add this to your code for example:
public Tennisball() {
this(0, 0, 0, 0, null) ;
} Hope that helped you out!
Thanks,
Nikolas.
PS any duke dollars would be much appreciated as i'm
very poor at the moment :-)I dont mean to be offensive just thought I should clarify these points
Michael -
Applet - JavaPurse does not have a public constructor
Hello,
I'm starting playing with Javacard and I tried to compile a demo of Java purse Applet.
I can compile it withou problem but once I try to start it with JBuilder 2006 I get the following error :
The applet com.sun.javacard.samples.JavaPurse.JavaPurse does not have a public constructor com.sun.javacard.samples.JavaPurse.JavaPurse()
Here is a part of my code
public class JavaPurse extends javacard.framework.Applet {
protected JavaPurse(byte[] bArray, short bOffset, byte bLength) {
public static void install(byte[] bArray, short bOffset, byte bLength) {
new JavaPurse(bArray, bOffset, bLength);
Does anyone of you know why JBuilder is displaying this error message?
Thanks in advance fo you reply.
Alain.I don't think that's the error message; there is no class "java.awt.Applet". Are you sure it doesn't say "java.applet.Applet"?
In any event, I don't know about javacard, but I suspect that javacard applets are not interchangeable with browser applets. My guess is that when JBuilder tries to build an applet, it's thinking about browser applets. Therefore it expects your applet to be a subclass of java.applet.Applet.
I don't know how JBuilder works, but perhaps you can try using normal compilation instead of whatever JBuilder provides for applets. -
Problem with threads within applet
Hello,
I got an applet, inside this applet I have a singleton, inside this singleton I have a thread.
this thread is running in endless loop.
he is doing something and go to sleep on and on.
the problem is,
when I refresh my IE6 browser I see more than 1 thread.
for debug matter, I did the following things:
inside the thread, sysout every time he goes to sleep.
sysout in the singleton constructor.
sysout in the singleton destructor.
the output goes like this:
when refresh the page, the singleton constructor loading but not every refresh, sometimes I see the constructor output and sometimes I dont.
The thread inside the singleton is giving me the same output, sometime I see more than one thread at a time and sometimes I dont.
The destructor never works (no output there).
I don't understand what is going on.
someone can please shed some light?
thanks.
btw. I am working with JRE 1.1
this is very old and big applet and I can't convert it to something new.Ooops. sorry!
I did.
public void start() {
public void stop() {
public void destroy() {
try {
resetAll();
Configuration.closeConnection();
QuoteItem.closeConnection();
} finally {
try {
super.finalize();
} catch (Throwable e) {
e.printStackTrace();
} -
Using getter/setter for returing a string variable to display on an Applet
have two classes called, class A and class testA.
class A contains an instance variable called title and one getter & setter method. class A as follow.
public class A extends Applet implements Runnable, KeyListener
//Use setter and getter of the instance variable
private String title;
public void init()
ASpriteFactory spriteFactory = ASpriteFactory.getSingleton();
// Find the size of the screen .
Dimension theDimension = getSize();
width = theDimension.width;
height = theDimension.height;
//Create new ship
ship = spriteFactory.createNewShip();
fwdThruster = spriteFactory.createForwardThruster();
revThruster = spriteFactory.createReverseThruster();
ufo = spriteFactory.createUfo();
missile = spriteFactory.createMissile();
generateStars();
generatePhotons();
generateAsteroids();
generateExplosions();
initializeFonts();
initializeGameData();
//Example from Instructor
//setMyControlPanel( new MyControlPanel(this) );
// new for JDK 1.2.2
addKeyListener(this);
requestFocus();
public void update(Graphics theGraphics)
// Create the offscreen graphics context, if no good one exists.
if (offGraphics == null || width != offDimension.width || height != offDimension.height)
// This better be the same as when the game was started
offDimension = getSize();
offImage = createImage(offDimension.width, offDimension.height);
offGraphics = offImage.getGraphics();
offGraphics.setFont(font);
displayStars();
displayPhotons();
displayMissile();
displayAsteroids();
displayUfo();
//displayShip();
//Load the game with different color of the space ship
displayNewShip();
displayExplosions();
displayStatus();
displayInfoScreen();
// Copy the off screen buffer to the screen.
theGraphics.drawImage(offImage, 0, 0, this);
private void displayInfoScreen()
String message;
if (!playing)
offGraphics.setColor(Color.white);
offGraphics.drawString("\'A\' to Change Font Attribute", 25, 35);
offGraphics.drawString(getTitle(), (width - fontMetrics.stringWidth(message)) / 2, height / 2
- fontHeight);
message = "The Training Mission";
offGraphics.drawString(message, (width - fontMetrics.stringWidth(message)) / 2, height / 2);
message = "Name of Author";
offGraphics.drawString(message, (width - fontMetrics.stringWidth(message)) / 2, height / 2
+ fontHeight);
message = "Original Copyright 1998-1999 by Mike Hall";
offGraphics.drawString(message, (width - fontMetrics.stringWidth(message)) / 2, height / 2
+ (fontHeight * 2));
if (!loaded)
message = "Loading sounds...";
int barWidth = 4 * fontWidth + fontMetrics.stringWidth(message);
int barHeight = fontHeight;
int startX = (width - barWidth) / 2;
int startY = 3 * height / 4 - fontMetrics.getMaxAscent();
offGraphics.setColor(Color.black);
offGraphics.fillRect(startX, startY, barWidth, barHeight);
offGraphics.setColor(Color.gray);
if (clipTotal > 0)
offGraphics.fillRect(startX, startY, (barWidth * clipsLoaded / clipTotal), barHeight);
offGraphics.setColor(Color.white);
offGraphics.drawRect(startX, startY, barWidth, barHeight);
offGraphics
.drawString(message, startX + 2 * fontWidth, startY + fontMetrics.getMaxAscent());
else
message = "Game Over";
offGraphics.drawString(message, (width - fontMetrics.stringWidth(message)) / 2, height / 4);
message = "'S' to Start";
offGraphics.drawString(message, (width - fontMetrics.stringWidth(message)) / 2, height / 4
+ fontHeight);
else if (paused)
offGraphics.setColor(Color.white);
message = "Game Paused";
offGraphics.drawString(message, (width - fontMetrics.stringWidth(message)) / 2, height / 4);
public String getTitle() {
System.out.print(title);
return title;
public void setTitle(String title) {
this.title = title;
}displayInfoScreen method in class A calls out for getTitle( ) to be displayed on an applet as an initial display string for the application.
The instance variable title is set by setTitle method which is called out in class testA as follow,
public class testA extends TestCase
* testASprite constructor comment.
* @param name
* java.lang.String
public testA(String name)
super(name);
* Insert the method's description here.
* @param args
* java.lang.String[]
public static void main(String[] args)
junit.textui.TestRunner.run(suite());
// need to figure out how to get rid of the frame in this test
System.exit(0);
public static Test suite()
return new TestSuite(testA.class);
* Basic create and simple checks
public void testCreate()
A theGame = new A();
assertNotNull("game was null!", theGame);
* Basic create and simple checks
public void testInit()
A theGame = new A();
Frame gameFrame = new Frame("THE GAME");
gameFrame.add(theGame);
int width = 640;
int height = 480;
gameFrame.setSize(width, height);
// must pack to get graphics peer
gameFrame.pack();
theGame.resize(width, height);
theGame.setTitle("TEST THE GAME");
theGame.init();
assertEquals("ASprite width not set", A.width, width);
gameFrame.dispose();
gameFrame.remove(theGame);
}Basically, class testA invokes the init( ) method in class A and start the applet application. However, it displays a white blank display. If I change the getTitle( ) in the displayInfoScreen method to a fixed string, it works fine. Did I forget anything as far as using getter & setter method? Do I have to specify some type of handle to sync between setter and getter between two classes? Any feedback will be greatly appreciated.
Thanks.Your class A extends runnable which leads me to believe that this is a multi-threaded application. In that case, title may or may not be a shared variable. Who knows? It's impossible to tell from what you posted.
Anyway, what is happening is that your applet is being painted by the JFrame before setTitle is called. After that, who knows what's happening. It's a complicated application. I suspect that if you called setTitle before you added the applet to the frame, it would work. -
Hi everyone.I need to convert graphics from JFrame to Japplet. I am using a class which contains the main method the main method runs the constructor of my class and the constructor creates a new object which is a class that extends to Jframe.I need to make this program to run in an Internet Explorer.Any ideas Please help me guys It is impossible to change the whole program. Thanx in advance.
Your JFrame extended class functionality should be put into the JApplet's
functionality. Probably mostly in the init method.
You could launch JFrames from within an Applet. But I'm not sure why
you wouldn't just migrate everything your JFrame does. -
Problem converting a (working) Java program into an applet
When I'm trying to access an Image through a call to :
mediaTracker = new MediaTracker(this);
backGroundImage = getImage(getDocumentBase(), "background.gif");
mediaTracker.addImage(backGroundImage, 0);
I'm getting a nullPointerException as a result of the call to getDocumentBase() :
C:\Chantier\Java\BallsApplet
AppletViewer testBallsApplet.htmljava.lang.NullPointerException
at java.applet.Applet.getDocumentBase(Applet.java:125)
at Balls.<init>(Balls.java:84)
at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstruct
orAccessorImpl.java:39)
at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingC
onstructorAccessorImpl.java:27)
at java.lang.reflect.Constructor.newInstance(Constructor.java:274)
at java.lang.Class.newInstance0(Class.java:296)
at java.lang.Class.newInstance(Class.java:249)
at sun.applet.AppletPanel.createApplet(AppletPanel.java:548)
at sun.applet.AppletPanel.runLoader(AppletPanel.java:477)
at sun.applet.AppletPanel.run(AppletPanel.java:290)
at java.lang.Thread.run(Thread.java:536)
It seems very weird to me... :-/
(all the .gif files are in the same directory than the .class files)
The problem appears with AppletViewer trying to open an HTML file
containing :
<HTML>
<APPLET CODE="Balls.class" WIDTH=300 HEIGHT=211>
</APPLET>
</HTML>
(I tried unsuccessfully the CODEBASE and ARCHIVE attributes, with and without putting the .gif and .class into a .jar file)
I can't find the solution by myself, so, I'd be very glad if someone could help
me with this... Thank you very much in advance ! :-)
You'll find below the source of a small game that I wrote and debugged (without
problem) and that I'm now (unsuccessfully) trying to convert into an Applet :
import java.applet.Applet;
import java.awt.*;
import java.awt.event.*;
import java.util.*;
import java.net.URL;
public class Balls extends java.applet.Applet implements Runnable, KeyListener
private Image offScreenImage;
private Image backGroundImage;
private Image[] gifImages = new Image[6];
private Image PressStart ;
private Sprite pressStartSprite = null ;
private Image YouLose ;
private Sprite YouLoseSprite = null ;
private Image NextStage ;
private Sprite NextStageSprite = null ;
private Image GamePaused ;
private Sprite GamePausedSprite = null ;
//offscreen graphics context
private Graphics offScreenGraphicsCtx;
private Thread animationThread;
private MediaTracker mediaTracker;
private SpriteManager spriteManager;
//Animation display rate, 12fps
private int animationDelay = 83;
private Random rand = new Random(System.currentTimeMillis());
private int message = 0 ; // 0 = no message (normal playing phase)
// 1 = press space to start
// 2 = press space for next level
// 3 = game PAUSED, press space to unpause
// 4 = You LOSE
public static void main(String[] args)
try
new Balls() ;
catch (java.net.MalformedURLException e)
System.out.println(e);
}//end main
public void start()
//Create and start animation thread
animationThread = new Thread(this);
animationThread.start();
public void init()
try
new Balls() ;
catch (java.net.MalformedURLException e)
System.out.println(e);
public Balls() throws java.net.MalformedURLException
{//constructor
// Load and track the images
mediaTracker = new MediaTracker(this);
backGroundImage = getImage(getDocumentBase(), "background.gif");
mediaTracker.addImage(backGroundImage, 0);
PressStart = getImage(getDocumentBase(), "press_start.gif");
mediaTracker.addImage(PressStart, 0);
NextStage = getImage(getDocumentBase(), "stage_complete.gif");
mediaTracker.addImage(NextStage, 0);
GamePaused = getImage(getDocumentBase(), "game_paused.gif");
mediaTracker.addImage(GamePaused, 0);
YouLose = getImage(getDocumentBase(), "you_lose.gif");
mediaTracker.addImage(YouLose, 0);
//Get and track 6 images to use
// for sprites
gifImages[0] = getImage(getDocumentBase(), "blueball.gif");
mediaTracker.addImage(gifImages[0], 0);
gifImages[1] = getImage(getDocumentBase(), "redball.gif");
mediaTracker.addImage(gifImages[1], 0);
gifImages[2] = getImage(getDocumentBase(), "greenball.gif");
mediaTracker.addImage(gifImages[2], 0);
gifImages[3] = getImage(getDocumentBase(), "yellowball.gif");
mediaTracker.addImage(gifImages[3], 0);
gifImages[4] = getImage(getDocumentBase(), "purpleball.gif");
mediaTracker.addImage(gifImages[4], 0);
gifImages[5] = getImage(getDocumentBase(), "orangeball.gif");
mediaTracker.addImage(gifImages[5], 0);
//Block and wait for all images to
// be loaded
try {
mediaTracker.waitForID(0);
}catch (InterruptedException e) {
System.out.println(e);
}//end catch
//Base the Frame size on the size
// of the background image.
//These getter methods return -1 if
// the size is not yet known.
//Insets will be used later to
// limit the graphics area to the
// client area of the Frame.
int width = backGroundImage.getWidth(this);
int height = backGroundImage.getHeight(this);
//While not likely, it may be
// possible that the size isn't
// known yet. Do the following
// just in case.
//Wait until size is known
while(width == -1 || height == -1)
System.out.println("Waiting for image");
width = backGroundImage.getWidth(this);
height = backGroundImage.getHeight(this);
}//end while loop
//Display the frame
setSize(width,height);
setVisible(true);
//setTitle("Balls");
//Anonymous inner class window
// listener to terminate the
// program.
this.addWindowListener
(new WindowAdapter()
{public void windowClosing(WindowEvent e){System.exit(0);}});
// Add a key listener for keyboard management
this.addKeyListener(this);
}//end constructor
public void run()
Point center_place = new Point(
backGroundImage.getWidth(this)/2-PressStart.getWidth(this)/2,
backGroundImage.getHeight(this)/2-PressStart.getHeight(this)/2) ;
pressStartSprite = new Sprite(this, PressStart, center_place, new Point(0, 0),true);
center_place = new Point(
backGroundImage.getWidth(this)/2-NextStage.getWidth(this)/2,
backGroundImage.getHeight(this)/2-NextStage.getHeight(this)/2) ;
NextStageSprite = new Sprite(this, NextStage, center_place, new Point(0, 0),true);
center_place = new Point(
backGroundImage.getWidth(this)/2-GamePaused.getWidth(this)/2,
backGroundImage.getHeight(this)/2-GamePaused.getHeight(this)/2) ;
GamePausedSprite = new Sprite(this, GamePaused, center_place, new Point(0, 0),true);
center_place = new Point(
backGroundImage.getWidth(this)/2-YouLose.getWidth(this)/2,
backGroundImage.getHeight(this)/2-YouLose.getHeight(this)/2) ;
YouLoseSprite = new Sprite(this, YouLose, center_place, new Point(0, 0),true);
BackgroundImage bgimage = new BackgroundImage(this, backGroundImage) ;
for (;;) // infinite loop
long time = System.currentTimeMillis();
message = 1 ; // "press start to begin"
while (message != 0)
repaint() ;
try
time += animationDelay;
Thread.sleep(Math.max(0,time - System.currentTimeMillis()));
catch (InterruptedException e)
System.out.println(e);
}//end catch
boolean you_lose = false ;
for (int max_speed = 7 ; !you_lose && max_speed < 15 ; max_speed++)
for (int difficulty = 2 ; !you_lose && difficulty < 14 ; difficulty++)
boolean unfinished_stage = true ;
spriteManager = new SpriteManager(bgimage);
spriteManager.setParameters(difficulty, max_speed) ;
//Create 15 sprites from 6 gif
// files.
for (int cnt = 0; cnt < 15; cnt++)
if (cnt == 0)
Point position = new Point(
backGroundImage.getWidth(this)/2-gifImages[0].getWidth(this)/2,
backGroundImage.getHeight(this)/2-gifImages[0].getHeight(this)/2) ;
spriteManager.addSprite(makeSprite(position, 0, false));
else
Point position = spriteManager.
getEmptyPosition(new Dimension(gifImages[0].getWidth(this),
gifImages[0].getHeight(this)));
if (cnt < difficulty)
spriteManager.addSprite(makeSprite(position, 1, true));
else
spriteManager.addSprite(makeSprite(position, 2, true));
}//end for loop
time = System.currentTimeMillis();
while (!spriteManager.getFinishedStage() && !spriteManager.getGameOver())
// Loop, sleep, and update sprite
// positions once each 83
// milliseconds
spriteManager.update();
repaint();
try
time += animationDelay;
Thread.sleep(Math.max(0,time - System.currentTimeMillis()));
catch (InterruptedException e)
System.out.println(e);
}//end catch
}//end while loop
if (spriteManager.getGameOver())
message = 4 ;
while (message != 0)
spriteManager.update();
repaint();
try
time += animationDelay;
Thread.sleep(Math.max(0,time - System.currentTimeMillis()));
catch (InterruptedException e)
System.out.println(e);
}//end catch
you_lose = true ;
if (spriteManager.getFinishedStage())
message = 2 ;
while (message != 0)
spriteManager.update();
repaint();
try
time += animationDelay;
Thread.sleep(Math.max(0,time - System.currentTimeMillis()));
catch (InterruptedException e)
System.out.println(e);
}//end catch
} // end for difficulty loop
} // end for max_speed
} // end infinite loop
}//end run method
private Sprite makeSprite(Point position, int imageIndex, boolean wind)
return new Sprite(
this,
gifImages[imageIndex],
position,
new Point(rand.nextInt() % 5,
rand.nextInt() % 5),
wind);
}//end makeSprite()
//Overridden graphics update method
// on the Frame
public void update(Graphics g)
//Create the offscreen graphics
// context
if (offScreenGraphicsCtx == null)
offScreenImage = createImage(getSize().width,
getSize().height);
offScreenGraphicsCtx = offScreenImage.getGraphics();
}//end if
if (message == 0)
// Draw the sprites offscreen
spriteManager.drawScene(offScreenGraphicsCtx);
else if (message == 1)
pressStartSprite.drawSpriteImage(offScreenGraphicsCtx);
else if (message == 2)
NextStageSprite.drawSpriteImage(offScreenGraphicsCtx);
else if (message == 3)
GamePausedSprite.drawSpriteImage(offScreenGraphicsCtx);
else if (message == 4)
YouLoseSprite.drawSpriteImage(offScreenGraphicsCtx);
// Draw the scene onto the screen
if(offScreenImage != null)
g.drawImage(offScreenImage, 0, 0, this);
}//end if
}//end overridden update method
//Overridden paint method on the
// Frame
public void paint(Graphics g)
//Nothing required here. All
// drawing is done in the update
// method above.
}//end overridden paint method
// Methods to handle Keyboard event
public void keyPressed(KeyEvent evt)
int key = evt.getKeyCode(); // Keyboard code for the pressed key.
if (key == KeyEvent.VK_SPACE)
if (message != 0)
message = 0 ;
else
message = 3 ;
if (key == KeyEvent.VK_LEFT)
if (spriteManager != null)
spriteManager.goLeft() ;
else if (key == KeyEvent.VK_RIGHT)
if (spriteManager != null)
spriteManager.goRight() ;
else if (key == KeyEvent.VK_UP)
if (spriteManager != null)
spriteManager.goUp() ;
else if (key == KeyEvent.VK_DOWN)
if (spriteManager != null)
spriteManager.goDown() ;
if (spriteManager != null)
spriteManager.setMessage(message) ;
public void keyReleased(KeyEvent evt)
public void keyTyped(KeyEvent e)
char key = e.getKeyChar() ;
//~ if (key == 's')
//~ stop = true ;
//~ else if (key == 'c')
//~ stop = false ;
//~ spriteManager.setStop(stop) ;
}//end class Balls
//===================================//
class BackgroundImage
private Image image;
private Component component;
private Dimension size;
public BackgroundImage(
Component component,
Image image)
this.component = component;
size = component.getSize();
this.image = image;
}//end construtor
public Dimension getSize(){
return size;
}//end getSize()
public Image getImage(){
return image;
}//end getImage()
public void setImage(Image image){
this.image = image;
}//end setImage()
public void drawBackgroundImage(Graphics g)
g.drawImage(image, 0, 0, component);
}//end drawBackgroundImage()
}//end class BackgroundImage
//===========================
class SpriteManager extends Vector
private BackgroundImage backgroundImage;
private boolean finished_stage = false ;
private boolean game_over = false ;
private int difficulty ;
private int max_speed ;
public boolean getFinishedStage()
finished_stage = true ;
for (int cnt = difficulty ; cnt < size(); cnt++)
Sprite sprite = (Sprite)elementAt(cnt);
if (!sprite.getEaten())
finished_stage = false ;
return finished_stage ;
public boolean getGameOver() {return game_over ;}
public void setParameters(int diff, int speed)
difficulty = diff ;
max_speed = speed ;
finished_stage = false ;
game_over = false ;
Sprite sprite;
for (int cnt = 0;cnt < size(); cnt++)
sprite = (Sprite)elementAt(cnt);
sprite.setSpeed(max_speed) ;
public SpriteManager(BackgroundImage backgroundImage)
this.backgroundImage = backgroundImage ;
}//end constructor
public Point getEmptyPosition(Dimension spriteSize)
Rectangle trialSpaceOccupied = new Rectangle(0, 0,
spriteSize.width,
spriteSize.height);
Random rand = new Random(System.currentTimeMillis());
boolean empty = false;
int numTries = 0;
// Search for an empty position
while (!empty && numTries++ < 100)
// Get a trial position
trialSpaceOccupied.x =
Math.abs(rand.nextInt() %
backgroundImage.
getSize().width);
trialSpaceOccupied.y =
Math.abs(rand.nextInt() %
backgroundImage.
getSize().height);
// Iterate through existing
// sprites, checking if position
// is empty
boolean collision = false;
for(int cnt = 0;cnt < size(); cnt++)
Rectangle testSpaceOccupied = ((Sprite)elementAt(cnt)).getSpaceOccupied();
if (trialSpaceOccupied.intersects(testSpaceOccupied))
collision = true;
}//end if
}//end for loop
empty = !collision;
}//end while loop
return new Point(trialSpaceOccupied.x, trialSpaceOccupied.y);
}//end getEmptyPosition()
public void update()
Sprite sprite;
// treat special case of sprite #0 (the player)
sprite = (Sprite)elementAt(0);
sprite.updatePosition() ;
int hitIndex = testForCollision(sprite);
if (hitIndex != -1)
if (hitIndex < difficulty)
{ // if player collides with an hunter (red ball), he loose
sprite.setEaten() ;
game_over = true ;
else
// if player collides with an hunted (green ball), he eats the green
((Sprite)elementAt(hitIndex)).setEaten() ;
//Iterate through sprite list
for (int cnt = 1;cnt < size(); cnt++)
sprite = (Sprite)elementAt(cnt);
//Update a sprite's position
sprite.updatePosition();
//Test for collision. Positive
// result indicates a collision
hitIndex = testForCollision(sprite);
if (hitIndex >= 0)
//a collision has occurred
bounceOffSprite(cnt,hitIndex);
}//end if
}//end for loop
}//end update
public void setMessage(int message)
Sprite sprite;
//Iterate through sprite list
for (int cnt = 0;cnt < size(); cnt++)
sprite = (Sprite)elementAt(cnt);
//Update a sprite's stop status
sprite.setMessage(message);
}//end for loop
}//end update
public void goLeft()
Sprite sprite = (Sprite)elementAt(0);
sprite.goLeft() ;
public void goRight()
Sprite sprite = (Sprite)elementAt(0);
sprite.goRight() ;
public void goUp()
Sprite sprite = (Sprite)elementAt(0);
sprite.goUp() ;
public void goDown()
Sprite sprite = (Sprite)elementAt(0);
sprite.goDown() ;
private int testForCollision(Sprite testSprite)
//Check for collision with other
// sprites
Sprite sprite;
for (int cnt = 0;cnt < size(); cnt++)
sprite = (Sprite)elementAt(cnt);
if (sprite == testSprite)
//don't check self
continue;
//Invoke testCollision method
// of Sprite class to perform
// the actual test.
if (testSprite.testCollision(sprite))
//Return index of colliding
// sprite
return cnt;
}//end for loop
return -1;//No collision detected
}//end testForCollision()
private void bounceOffSprite(int oneHitIndex, int otherHitIndex)
//Swap motion vectors for
// bounce algorithm
Sprite oneSprite = (Sprite)elementAt(oneHitIndex);
Sprite otherSprite = (Sprite)elementAt(otherHitIndex);
Point swap = oneSprite.getMotionVector();
oneSprite.setMotionVector(otherSprite.getMotionVector());
otherSprite.setMotionVector(swap);
}//end bounceOffSprite()
public void drawScene(Graphics g)
//Draw the background and erase
// sprites from graphics area
//Disable the following statement
// for an interesting effect.
backgroundImage.drawBackgroundImage(g);
//Iterate through sprites, drawing
// each sprite
for (int cnt = 0;cnt < size(); cnt++)
((Sprite)elementAt(cnt)).drawSpriteImage(g);
}//end drawScene()
public void addSprite(Sprite sprite)
addElement(sprite);
}//end addSprite()
}//end class SpriteManager
//===================================//
class Sprite
private Component component;
private Image image;
private Rectangle spaceOccupied;
private Point motionVector;
private Rectangle bounds;
private Random rand;
private int message = 0 ; // number of message currently displayed (0 means "no message" = normal game)
private int max_speed = 7 ;
private boolean eaten = false ; // when a green sprite is eaten, it is no longer displayed on screen
private boolean wind = true ;
private boolean go_left = false ;
private boolean go_right = false ;
private boolean go_up = false ;
private boolean go_down = false ;
public Sprite(Component component,
Image image,
Point position,
Point motionVector,
boolean Wind
//Seed a random number generator
// for this sprite with the sprite
// position.
rand = new Random(position.x);
this.component = component;
this.image = image;
setSpaceOccupied(new Rectangle(
position.x,
position.y,
image.getWidth(component),
image.getHeight(component)));
this.motionVector = motionVector;
this.wind = Wind ;
//Compute edges of usable graphics
// area in the Frame.
int topBanner = ((Container)component).getInsets().top;
int bottomBorder = ((Container)component).getInsets().bottom;
int leftBorder = ((Container)component).getInsets().left;
int rightBorder = ((Container)component).getInsets().right;
bounds = new Rectangle( 0 + leftBorder, 0 + topBanner
, component.getSize().width - (leftBorder + rightBorder)
, component.getSize().height - (topBanner + bottomBorder));
}//end constructor
public void setMessage(int message_number)
message = message_number ;
public void setSpeed(int speed)
max_speed = speed ;
public void goLeft()
go_left = true ;
public void goRight()
go_right = true ;
public void goUp()
go_up = true ;
public void goDown()
go_down = true ;
public void setEaten()
eaten = true ;
setSpaceOccupied(new Rectangle(4000,4000,0,0)) ;
public boolean getEaten()
return eaten ;
public Rectangle getSpaceOccupied()
return spaceOccupied;
}//end getSpaceOccupied()
void setSpaceOccupied(Rectangle spaceOccupied)
this.spaceOccupied = spaceOccupied;
}//setSpaceOccupied()
public void setSpaceOccupied(
Point position){
spaceOccupied.setLocation(
position.x, position.y);
}//setSpaceOccupied()
public Point getMotionVector(){
return motionVector;
}//end getMotionVector()
public void setMotionVector(
Point motionVector){
this.motionVector = motionVector;
}//end setMotionVector()
public void setBounds(Rectangle bounds)
this.bounds = bounds;
}//end setBounds()
public void updatePosition()
Point position = new Point(spaceOccupied.x, spaceOccupied.y);
if (message != 0)
return ;
//Insert random behavior. During
// each update, a sprite has about
// one chance in 10 of making a
// random change to its
// motionVector. When a change
// occurs, the motionVector
// coordinate values are forced to
// fall between -7 and 7. This
// puts a cap on the maximum speed
// for a sprite.
if (!wind)
if (go_left)
motionVector.x -= 2 ;
if (motionVector.x < -15)
motionVector.x = -14 ;
go_left = false ;
if (go_right)
motionVector.x += 2 ;
if (motionVector.x > 15)
motionVector.x = 14 ;
go_right = false ;
if (go_up)
motionVector.y -= 2 ;
if (motionVector.y < -15)
motionVector.y = -14 ;
go_up = false ;
if (go_down)
motionVector.y += 2 ;
if (motionVector.y > 15)
motionVector.y = 14 ;
go_down = false ;
else if(rand.nextInt() % 7 == 0)
Point randomOffset =
new Point(rand.nextInt() % 3,
rand.nextInt() % 3);
motionVector.x += randomOffset.x;
if(motionVector.x >= max_speed)
motionVector.x -= max_speed;
if(motionVector.x <= -max_speed)
motionVector.x += max_speed ;
motionVector.y += randomOffset.y;
if(motionVector.y >= max_speed)
motionVector.y -= max_speed;
if(motionVector.y <= -max_speed)
motionVector.y += max_speed;
}//end if
//Move the sprite on the screen
position.translate(motionVector.x, motionVector.y);
//Bounce off the walls
boolean bounceRequired = false;
Point tempMotionVector = new Point(
motionVector.x,
motionVector.y);
//Handle walls in x-dimension
if (position.x < bounds.x)
bounceRequired = true;
position.x = bounds.x;
//reverse direction in x
tempMotionVector.x = -tempMotionVector.x;
else if ((position.x + spaceOccupied.width) > (bounds.x + bounds.width))
bounceRequired = true;
position.x = bounds.x +
bounds.width -
spaceOccupied.width;
//reverse direction in x
tempMotionVector.x =
-tempMotionVector.x;
}//end else if
//Handle walls in y-dimension
if (position.y < bounds.y)
bounceRequired = true;
position.y = bounds.y;
tempMotionVector.y = -tempMotionVector.y;
else if ((position.y + spaceOccupied.height)
> (bounds.y + bounds.height))
bounceRequired = true;
position.y = bounds.y +
bounds.height -
spaceOccupied.height;
tempMotionVector.y =
-tempMotionVector.y;
}//end else if
if(bounceRequired)
//save new motionVector
setMotionVector(
tempMotionVector);
//update spaceOccupied
setSpaceOccupied(position);
}//end updatePosition()
public void drawSpriteImage(Graphics g)
if (!eaten)
g.drawImage(image,
spaceOccupied.x,
spaceOccupied.y,
component);
}//end drawSpriteImage()
public boolean testCollision(Sprite testSprite)
//Check for collision with
// another sprite
if (testSprite != this)
return spaceOccupied.intersects(
testSprite.getSpaceOccupied());
}//end if
return false;
}//end testCollision
}//end Sprite class
//===================================//
Thanks for your help...Sorry,
Can you tell me how do you solve it because I have got the same problem.
Can you indicate me the topic where did you find solution.
Thank in advance. -
Please help, Applet and JInternalFrame
Hi,
I have EXHAUSTEDresearch but to no avail on how to make the internal frame title ... closing button visible
Currently it just covers up the entire area with the JInternalFrame
The folwing is the code form the applet class
//JDesktopPane desktop = new JDesktopPane();
JDesktopPane desktop = new JDesktopPane();
SectionE obj = new SectionE();
//desktop.add(obj);
desktop.add(obj);
setContentPane(desktop);
desktop.setDragMode(JDesktopPane.OUTLINE_DRAG_MODE);
//setVisible(true);
The internal frame is made from a class whic extends JInternalFrame and only has the following constructor
public SectionE ()
super("Document #",
true, //resizable
true, //closable
false,
true);
setVisible(true);
try {
setSelected(true);
} catch (java.beans.PropertyVetoException k) {k.printStackTrace();}
}obj.setBounds(100,100,100,100);
-
How do I convert this Applet to launch from a JFrame instead??
A simple program where the user can sketch curves and shapes in a
variety of colors on a variety of background colors. The user selects
a drawing color form a pop-up menu at the top of the
applet. If the user clicks "Set Background", the background
color is set to the current drawing color and the drawing
area is filled with that color. If the user clicks "Clear",
the drawing area is just filled with the current background color.
The user selects the shape to draw from another pop-up menu at the
top of the applet. The user can draw free-hand curves, straight
lines, and one of six different types of shapes.
The user's drawing is saved in an off-screen image, which is
used to refresh the screen when repainting. The picture is
lost if the applet changes size, however.
This file defines two classes, SimplePaint3,class, and
class, SimplePaint3$Display.class.
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
public class SimplePaint3 extends JApplet {
// The main applet class simply sets up the applet. Most of the
// work is done in the Display class.
JComboBox colorChoice, figureChoice; // Pop-up menus, defined as instance
// variables so that the Display
// class can see them.
public void init() {
setBackground(Color.gray);
getContentPane().setBackground(Color.gray);
Display canvas = new Display(); // The drawing area.
getContentPane().add(canvas,BorderLayout.CENTER);
JPanel buttonBar = new JPanel(); // A panel to hold the buttons.
buttonBar.setBackground(Color.gray);
getContentPane().add(buttonBar, BorderLayout.SOUTH);
JPanel choiceBar = new JPanel(); // A panel to hole the pop-up menus
choiceBar.setBackground(Color.gray);
getContentPane().add(choiceBar, BorderLayout.NORTH);
JButton fill = new JButton("Set Background"); // The first button.
fill.addActionListener(canvas);
buttonBar.add(fill);
JButton clear = new JButton("Clear"); // The second button.
clear.addActionListener(canvas);
buttonBar.add(clear);
colorChoice = new JComboBox(); // The pop-up menu of colors.
colorChoice.addItem("Black");
colorChoice.addItem("Red");
colorChoice.addItem("Green");
colorChoice.addItem("Blue");
colorChoice.addItem("Cyan");
colorChoice.addItem("Magenta");
colorChoice.addItem("Yellow");
colorChoice.addItem("White");
colorChoice.setBackground(Color.white);
choiceBar.add(colorChoice);
figureChoice = new JComboBox(); // The pop-up menu of shapes.
figureChoice.addItem("Curve");
figureChoice.addItem("Straight Line");
figureChoice.addItem("Rectangle");
figureChoice.addItem("Oval");
figureChoice.addItem("RoundRect");
figureChoice.addItem("Filled Rectangle");
figureChoice.addItem("Filled Oval");
figureChoice.addItem("Filled RoundRect");
figureChoice.setBackground(Color.white);
choiceBar.add(figureChoice);
} // end init()
public Insets getInsets() {
// Specify how wide a border to leave around the edges of the applet.
return new Insets(3,3,3,3);
private class Display extends JPanel
implements MouseListener, MouseMotionListener, ActionListener {
// Nested class Display represents the drawing surface of the
// applet. It lets the user use the mouse to draw colored curves
// and shapes. The current color is specified by the pop-up menu
// colorChoice. The current shape is specified by another pop-up menu,
// figureChoice. (These are instance variables in the main class.)
// The panel also listens for action events from buttons
// named "Clear" and "Set Background". The "Clear" button fills
// the panel with the current background color. The "Set Background"
// button sets the background color to the current drawing color and
// then clears. These buttons are set up in the main class.
private final static int
BLACK = 0,
RED = 1, // Some constants to make
GREEN = 2, // the code more readable.
BLUE = 3, // These numbers code for
CYAN = 4, // the different drawing colors.
MAGENTA = 5,
YELLOW = 6,
WHITE = 7;
private final static int
CURVE = 0,
LINE = 1,
RECT = 2, // Some constants that code
OVAL = 3, // for the different types of
ROUNDRECT = 4, // figure the program can draw.
FILLED_RECT = 5,
FILLED_OVAL = 6,
FILLED_ROUNDRECT = 7;
/* Some variables used for backing up the contents of the panel. */
Image OSI; // The off-screen image (created in checkOSI()).
int widthOfOSI, heightOfOSI; // Current width and height of OSI. These
// are checked against the size of the applet,
// to detect any change in the panel's size.
// If the size has changed, a new OSI is created.
// The picture in the off-screen image is lost
// when that happens.
/* The following variables are used when the user is sketching a
curve while dragging a mouse. */
private int mouseX, mouseY; // The location of the mouse.
private int prevX, prevY; // The previous location of the mouse.
private int startX, startY; // The starting position of the mouse.
// (Not used for drawing curves.)
private boolean dragging; // This is set to true when the user is drawing.
private int figure; // What type of figure is being drawn. This is
// specified by the figureChoice menu.
private Graphics dragGraphics; // A graphics context for the off-screen image,
// to be used while a drag is in progress.
private Color dragColor; // The color that is used for the figure that is
// being drawn.
Display() {
// Constructor. When this component is first created, it is set to
// listen for mouse events and mouse motion events from
// itself. The initial background color is white.
addMouseListener(this);
addMouseMotionListener(this);
setBackground(Color.white);
private void drawFigure(Graphics g, int shape, int x1, int y1, int x2, int y2) {
// This method is called to do ALL drawing in this applet!
// Draws a shape in the graphics context g.
// The shape paramter tells what kind of shape to draw. This
// can be LINE, RECT, OVAL, ROUNTRECT, FILLED_RECT,
// FILLED_OVAL, or FILLED_ROUNDRECT. (Note that a CURVE is
// drawn by drawing multiple LINES, so the shape parameter is
// never equal to CURVE.) For a LINE, a line is drawn from
// the point (x1,y1) to (x2,y2). For other shapes, the
// points (x1,y1) and (x2,y2) give two corners of the shape
// (or of a rectangle that contains the shape).
if (shape == LINE) {
// For a line, just draw the line between the two points.
g.drawLine(x1,y1,x2,y2);
return;
int x, y; // Top left corner of rectangle that contains the figure.
int w, h; // Width and height of rectangle that contains the figure.
if (x1 >= x2) { // x2 is left edge
x = x2;
w = x1 - x2;
else { // x1 is left edge
x = x1;
w = x2 - x1;
if (y1 >= y2) { // y2 is top edge
y = y2;
h = y1 - y2;
else { // y1 is top edge.
y = y1;
h = y2 - y1;
switch (shape) { // Draw the appropriate figure.
case RECT:
g.drawRect(x, y, w, h);
break;
case OVAL:
g.drawOval(x, y, w, h);
break;
case ROUNDRECT:
g.drawRoundRect(x, y, w, h, 20, 20);
break;
case FILLED_RECT:
g.fillRect(x, y, w, h);
break;
case FILLED_OVAL:
g.fillOval(x, y, w, h);
break;
case FILLED_ROUNDRECT:
g.fillRoundRect(x, y, w, h, 20, 20);
break;
private void repaintRect(int x1, int y1, int x2, int y2) {
// Call repaint on a rectangle that contains the points (x1,y1)
// and (x2,y2). (Add a 1-pixel border along right and bottom
// edges to allow for the pen overhang when drawing a line.)
int x, y; // top left corner of rectangle that contains the figure
int w, h; // width and height of rectangle that contains the figure
if (x2 >= x1) { // x1 is left edge
x = x1;
w = x2 - x1;
else { // x2 is left edge
x = x2;
w = x1 - x2;
if (y2 >= y1) { // y1 is top edge
y = y1;
h = y2 - y1;
else { // y2 is top edge.
y = y2;
h = y1 - y2;
repaint(x,y,w+1,h+1);
private void checkOSI() {
// This method is responsible for creating the off-screen image.
// It should be called before using the OSI. It will make a new OSI if
// the size of the panel changes.
if (OSI == null || widthOfOSI != getSize().width || heightOfOSI != getSize().height) {
// Create the OSI, or make a new one if panel size has changed.
OSI = null; // (If OSI already exists, this frees up the memory.)
OSI = createImage(getSize().width, getSize().height);
widthOfOSI = getSize().width;
heightOfOSI = getSize().height;
Graphics OSG = OSI.getGraphics(); // Graphics context for drawing to OSI.
OSG.setColor(getBackground());
OSG.fillRect(0, 0, widthOfOSI, heightOfOSI);
OSG.dispose();
public void paintComponent(Graphics g) {
// Copy the off-screen image to the screen,
// after checking to make sure it exists. Then,
// if a shape other than CURVE is being drawn,
// draw it on top of the image from the OSI.
checkOSI();
g.drawImage(OSI, 0, 0, this);
if (dragging && figure != CURVE) {
g.setColor(dragColor);
drawFigure(g,figure,startX,startY,mouseX,mouseY);
public void actionPerformed(ActionEvent evt) {
// Respond when the user clicks on a button. The
// command must be either "Clear" or "Set Background".
String command = evt.getActionCommand();
checkOSI();
if (command.equals("Set Background")) {
// Set background color before clearing.
// Change the selected color so it is different
// from the background color.
setBackground(getCurrentColor());
if (colorChoice.getSelectedIndex() == BLACK)
colorChoice.setSelectedIndex(WHITE);
else
colorChoice.setSelectedIndex(BLACK);
Graphics g = OSI.getGraphics();
g.setColor(getBackground());
g.fillRect(0,0,getSize().width,getSize().height);
g.dispose();
repaint();
private Color getCurrentColor() {
// Check the colorChoice menu to find the currently
// selected color, and return the appropriate color
// object.
int currentColor = colorChoice.getSelectedIndex();
switch (currentColor) {
case BLACK:
return Color.black;
case RED:
return Color.red;
case GREEN:
return Color.green;
case BLUE:
return Color.blue;
case CYAN:
return Color.cyan;
case MAGENTA:
return Color.magenta;
case YELLOW:
return Color.yellow;
default:
return Color.white;
public void mousePressed(MouseEvent evt) {
// This is called when the user presses the mouse on the
// panel. This begins a draw operation in which the user
// sketches a curve or draws a shape. (Note that curves
// are handled differently from other shapes. For CURVE,
// a new segment of the curve is drawn each time the user
// moves the mouse. For the other shapes, a "rubber band
// cursor" is used. That is, the figure is drawn between
// the starting point and the current mouse location.)
if (dragging == true) // Ignore mouse presses that occur
return; // when user is already drawing a curve.
// (This can happen if the user presses
// two mouse buttons at the same time.)
prevX = startX = evt.getX(); // Save mouse coordinates.
prevY = startY = evt.getY();
figure = figureChoice.getSelectedIndex();
dragColor = getCurrentColor();
dragGraphics = OSI.getGraphics();
dragGraphics.setColor(dragColor);
dragging = true; // Start drawing.
} // end mousePressed()
public void mouseReleased(MouseEvent evt) {
// Called whenever the user releases the mouse button.
// If the user was drawing a shape, we make the shape
// permanent by drawing it to the off-screen image.
if (dragging == false)
return; // Nothing to do because the user isn't drawing.
dragging = false;
mouseX = evt.getX();
mouseY = evt.getY();
if (figure == CURVE) {
// A CURVE is drawn as a series of LINEs
drawFigure(dragGraphics,LINE,prevX,prevY,mouseX,mouseY);
repaintRect(prevX,prevY,mouseX,mouseY);
else if (figure == LINE) {
repaintRect(startX,startY,prevX,prevY);
if (mouseX != startX || mouseY != startY) {
// Draw the line only if it has non-zero length.
drawFigure(dragGraphics,figure,startX,startY,mouseX,mouseY);
repaintRect(startX,startY,mouseX,mouseY);
else {
repaintRect(startX,startY,prevX,prevY);
if (mouseX != startX && mouseY != startY) {
// Draw the shape only if both its height
// and width are both non-zero.
drawFigure(dragGraphics,figure,startX,startY,mouseX,mouseY);
repaintRect(startX,startY,mouseX,mouseY);
dragGraphics.dispose();
dragGraphics = null;
public void mouseDragged(MouseEvent evt) {
// Called whenever the user moves the mouse while a mouse button
// is down. If the user is drawing a curve, draw a segment of
// the curve on the off-screen image, and repaint the part
// of the panel that contains the new line segment. Otherwise,
// just call repaint and let paintComponent() draw the shape on
// top of the picture in the off-screen image.
if (dragging == false)
return; // Nothing to do because the user isn't drawing.
mouseX = evt.getX(); // x-coordinate of mouse.
mouseY = evt.getY(); // y=coordinate of mouse.
if (figure == CURVE) {
// A CURVE is drawn as a series of LINEs.
drawFigure(dragGraphics,LINE,prevX,prevY,mouseX,mouseY);
repaintRect(prevX,prevY,mouseX,mouseY);
else {
// Repaint two rectangles: The one that contains the previous
// version of the figure, and the one that will contain the
// new version. The first repaint is necessary to restore
// the picture from the off-screen image in that rectangle.
repaintRect(startX,startY,prevX,prevY);
repaintRect(startX,startY,mouseX,mouseY);
prevX = mouseX; // Save coords for the next call to mouseDragged or mouseReleased.
prevY = mouseY;
} // end mouseDragged.
public void mouseEntered(MouseEvent evt) { } // Some empty routines.
public void mouseExited(MouseEvent evt) { } // (Required by the MouseListener
public void mouseClicked(MouseEvent evt) { } // and MouseMotionListener
public void mouseMoved(MouseEvent evt) { } // interfaces).
} // end nested class Display
} // end class SimplePaint3Im quite the novice, how exactly do I go about doing that. What I did was to put both in diff files but I got errors saying that they cant find colorChoice, figureChoice in the Display class.
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
public class Simple extends JFrame implements Display{
// The main applet class simply sets up the applet. Most of the
// work is done in the Display class.
JComboBox colorChoice, figureChoice; // Pop-up menus, defined as instance
// variables so that the Display
// class can see them.
public void init() {
setBackground(Color.gray);
getContentPane().setBackground(Color.gray);
Display canvas = new Display(); // The drawing area.
getContentPane().add(canvas,BorderLayout.CENTER);
JPanel buttonBar = new JPanel(); // A panel to hold the buttons.
buttonBar.setBackground(Color.gray);
getContentPane().add(buttonBar, BorderLayout.SOUTH);
JPanel choiceBar = new JPanel(); // A panel to hole the pop-up menus
choiceBar.setBackground(Color.gray);
getContentPane().add(choiceBar, BorderLayout.NORTH);
JButton fill = new JButton("Set Background"); // The first button.
fill.addActionListener(canvas);
buttonBar.add(fill);
JButton clear = new JButton("Clear"); // The second button.
clear.addActionListener(canvas);
buttonBar.add(clear);
colorChoice = new JComboBox(); // The pop-up menu of colors.
colorChoice.addItem("Black");
colorChoice.addItem("Red");
colorChoice.addItem("Green");
colorChoice.addItem("Blue");
colorChoice.addItem("Cyan");
colorChoice.addItem("Magenta");
colorChoice.addItem("Yellow");
colorChoice.addItem("White");
colorChoice.setBackground(Color.white);
choiceBar.add(colorChoice);
figureChoice = new JComboBox(); // The pop-up menu of shapes.
figureChoice.addItem("Curve");
figureChoice.addItem("Straight Line");
figureChoice.addItem("Rectangle");
figureChoice.addItem("Oval");
figureChoice.addItem("RoundRect");
figureChoice.addItem("Filled Rectangle");
figureChoice.addItem("Filled Oval");
figureChoice.addItem("Filled RoundRect");
figureChoice.setBackground(Color.white);
choiceBar.add(figureChoice);
} // end init()
} // end class SimplePaint3
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
class Display extends JPanel
implements MouseListener, MouseMotionListener, ActionListener {
// Nested class Display represents the drawing surface of the
// applet. It lets the user use the mouse to draw colored curves
// and shapes. The current color is specified by the pop-up menu
// colorChoice. The current shape is specified by another pop-up menu,
// figureChoice. (These are instance variables in the main class.)
// The panel also listens for action events from buttons
// named "Clear" and "Set Background". The "Clear" button fills
// the panel with the current background color. The "Set Background"
// button sets the background color to the current drawing color and
// then clears. These buttons are set up in the main class.
private final static int
BLACK = 0,
RED = 1, // Some constants to make
GREEN = 2, // the code more readable.
BLUE = 3, // These numbers code for
CYAN = 4, // the different drawing colors.
MAGENTA = 5,
YELLOW = 6,
WHITE = 7;
private final static int
CURVE = 0,
LINE = 1,
RECT = 2, // Some constants that code
OVAL = 3, // for the different types of
ROUNDRECT = 4, // figure the program can draw.
FILLED_RECT = 5,
FILLED_OVAL = 6,
FILLED_ROUNDRECT = 7;
/* Some variables used for backing up the contents of the panel. */
Image OSI; // The off-screen image (created in checkOSI()).
int widthOfOSI, heightOfOSI; // Current width and height of OSI. These
// are checked against the size of the applet,
// to detect any change in the panel's size.
// If the size has changed, a new OSI is created.
// The picture in the off-screen image is lost
// when that happens.
/* The following variables are used when the user is sketching a
curve while dragging a mouse. */
private int mouseX, mouseY; // The location of the mouse.
private int prevX, prevY; // The previous location of the mouse.
private int startX, startY; // The starting position of the mouse.
// (Not used for drawing curves.)
private boolean dragging; // This is set to true when the user is drawing.
private int figure; // What type of figure is being drawn. This is
// specified by the figureChoice menu.
private Graphics dragGraphics; // A graphics context for the off-screen image,
// to be used while a drag is in progress.
private Color dragColor; // The color that is used for the figure that is
// being drawn.
Display() {
// Constructor. When this component is first created, it is set to
// listen for mouse events and mouse motion events from
// itself. The initial background color is white.
addMouseListener(this);
addMouseMotionListener(this);
setBackground(Color.white);
private void drawFigure(Graphics g, int shape, int x1, int y1, int x2, int y2) {
// This method is called to do ALL drawing in this applet!
// Draws a shape in the graphics context g.
// The shape paramter tells what kind of shape to draw. This
// can be LINE, RECT, OVAL, ROUNTRECT, FILLED_RECT,
// FILLED_OVAL, or FILLED_ROUNDRECT. (Note that a CURVE is
// drawn by drawing multiple LINES, so the shape parameter is
// never equal to CURVE.) For a LINE, a line is drawn from
// the point (x1,y1) to (x2,y2). For other shapes, the
// points (x1,y1) and (x2,y2) give two corners of the shape
// (or of a rectangle that contains the shape).
if (shape == LINE) {
// For a line, just draw the line between the two points.
g.drawLine(x1,y1,x2,y2);
return;
int x, y; // Top left corner of rectangle that contains the figure.
int w, h; // Width and height of rectangle that contains the figure.
if (x1 >= x2) { // x2 is left edge
x = x2;
w = x1 - x2;
else { // x1 is left edge
x = x1;
w = x2 - x1;
if (y1 >= y2) { // y2 is top edge
y = y2;
h = y1 - y2;
else { // y1 is top edge.
y = y1;
h = y2 - y1;
switch (shape) { // Draw the appropriate figure.
case RECT:
g.drawRect(x, y, w, h);
break;
case OVAL:
g.drawOval(x, y, w, h);
break;
case ROUNDRECT:
g.drawRoundRect(x, y, w, h, 20, 20);
break;
case FILLED_RECT:
g.fillRect(x, y, w, h);
break;
case FILLED_OVAL:
g.fillOval(x, y, w, h);
break;
case FILLED_ROUNDRECT:
g.fillRoundRect(x, y, w, h, 20, 20);
break;
private void repaintRect(int x1, int y1, int x2, int y2) {
// Call repaint on a rectangle that contains the points (x1,y1)
// and (x2,y2). (Add a 1-pixel border along right and bottom
// edges to allow for the pen overhang when drawing a line.)
int x, y; // top left corner of rectangle that contains the figure
int w, h; // width and height of rectangle that contains the figure
if (x2 >= x1) { // x1 is left edge
x = x1;
w = x2 - x1;
else { // x2 is left edge
x = x2;
w = x1 - x2;
if (y2 >= y1) { // y1 is top edge
y = y1;
h = y2 - y1;
else { // y2 is top edge.
y = y2;
h = y1 - y2;
repaint(x,y,w+1,h+1);
private void checkOSI() {
// This method is responsible for creating the off-screen image.
// It should be called before using the OSI. It will make a new OSI if
// the size of the panel changes.
if (OSI == null || widthOfOSI != getSize().width || heightOfOSI != getSize().height) {
// Create the OSI, or make a new one if panel size has changed.
OSI = null; // (If OSI already exists, this frees up the memory.)
OSI = createImage(getSize().width, getSize().height);
widthOfOSI = getSize().width;
heightOfOSI = getSize().height;
Graphics OSG = OSI.getGraphics(); // Graphics context for drawing to OSI.
OSG.setColor(getBackground());
OSG.fillRect(0, 0, widthOfOSI, heightOfOSI);
OSG.dispose();
public void paintComponent(Graphics g) {
// Copy the off-screen image to the screen,
// after checking to make sure it exists. Then,
// if a shape other than CURVE is being drawn,
// draw it on top of the image from the OSI.
checkOSI();
g.drawImage(OSI, 0, 0, this);
if (dragging && figure != CURVE) {
g.setColor(dragColor);
drawFigure(g,figure,startX,startY,mouseX,mouseY);
public void actionPerformed(ActionEvent evt) {
// Respond when the user clicks on a button. The
// command must be either "Clear" or "Set Background".
String command = evt.getActionCommand();
checkOSI();
if (command.equals("Set Background")) {
// Set background color before clearing.
// Change the selected color so it is different
// from the background color.
setBackground(getCurrentColor());
if (colorChoice.getSelectedIndex() == BLACK)
colorChoice.setSelectedIndex(WHITE);
else
colorChoice.setSelectedIndex(BLACK);
Graphics g = OSI.getGraphics();
g.setColor(getBackground());
g.fillRect(0,0,getSize().width,getSize().height);
g.dispose();
repaint();
private Color getCurrentColor() {
// Check the colorChoice menu to find the currently
// selected color, and return the appropriate color
// object.
int currentColor = colorChoice.getSelectedIndex();
switch (currentColor) {
case BLACK:
return Color.black;
case RED:
return Color.red;
case GREEN:
return Color.green;
case BLUE:
return Color.blue;
case CYAN:
return Color.cyan;
case MAGENTA:
return Color.magenta;
case YELLOW:
return Color.yellow;
default:
return Color.white;
public void mousePressed(MouseEvent evt) {
// This is called when the user presses the mouse on the
// panel. This begins a draw operation in which the user
// sketches a curve or draws a shape. (Note that curves
// are handled differently from other shapes. For CURVE,
// a new segment of the curve is drawn each time the user
// moves the mouse. For the other shapes, a "rubber band
// cursor" is used. That is, the figure is drawn between
// the starting point and the current mouse location.)
if (dragging == true) // Ignore mouse presses that occur
return; // when user is already drawing a curve.
// (This can happen if the user presses
// two mouse buttons at the same time.)
prevX = startX = evt.getX(); // Save mouse coordinates.
prevY = startY = evt.getY();
figure = figureChoice.getSelectedIndex();
dragColor = getCurrentColor();
dragGraphics = OSI.getGraphics();
dragGraphics.setColor(dragColor);
dragging = true; // Start drawing.
} // end mousePressed()
public void mouseReleased(MouseEvent evt) {
// Called whenever the user releases the mouse button.
// If the user was drawing a shape, we make the shape
// permanent by drawing it to the off-screen image.
if (dragging == false)
return; // Nothing to do because the user isn't drawing.
dragging = false;
mouseX = evt.getX();
mouseY = evt.getY();
if (figure == CURVE) {
// A CURVE is drawn as a series of LINEs
drawFigure(dragGraphics,LINE,prevX,prevY,mouseX,mouseY);
repaintRect(prevX,prevY,mouseX,mouseY);
else if (figure == LINE) {
repaintRect(startX,startY,prevX,prevY);
if (mouseX != startX || mouseY != startY) {
// Draw the line only if it has non-zero length.
drawFigure(dragGraphics,figure,startX,startY,mouseX,mouseY);
repaintRect(startX,startY,mouseX,mouseY);
else {
repaintRect(startX,startY,prevX,prevY);
if (mouseX != startX && mouseY != startY) {
// Draw the shape only if both its height
// and width are both non-zero.
drawFigure(dragGraphics,figure,startX,startY,mouseX,mouseY);
repaintRect(startX,startY,mouseX,mouseY);
dragGraphics.dispose();
dragGraphics = null;
public void mouseDragged(MouseEvent evt) {
// Called whenever the user moves the mouse while a mouse button
// is down. If the user is drawing a curve, draw a segment of
// the curve on the off-screen image, and repaint the part
// of the panel that contains the new line segment. Otherwise,
// just call repaint and let paintComponent() draw the shape on
// top of the picture in the off-screen image.
if (dragging == false)
return; // Nothing to do because the user isn't drawing.
mouseX = evt.getX(); // x-coordinate of mouse.
mouseY = evt.getY(); // y=coordinate of mouse.
if (figure == CURVE) {
// A CURVE is drawn as a series of LINEs.
drawFigure(dragGraphics,LINE,prevX,prevY,mouseX,mouseY);
repaintRect(prevX,prevY,mouseX,mouseY);
else {
// Repaint two rectangles: The one that contains the previous
// version of the figure, and the one that will contain the
// new version. The first repaint is necessary to restore
// the picture from the off-screen image in that rectangle.
repaintRect(startX,startY,prevX,prevY);
repaintRect(startX,startY,mouseX,mouseY);
prevX = mouseX; // Save coords for the next call to mouseDragged or mouseReleased.
prevY = mouseY;
} // end mouseDragged.
public void mouseEntered(MouseEvent evt) { } // Some empty routines.
public void mouseExited(MouseEvent evt) { } // (Required by the MouseListener
public void mouseClicked(MouseEvent evt) { } // and MouseMotionListener
public void mouseMoved(MouseEvent evt) { } // interfaces).
} // end nested class Display
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