adding a second trail
How can I do it?
/**
**/
import java.awt.*;
import java.applet.Applet;
import java.net.URL;
import java.util.ArrayList;
import java.awt.event.*;
publicclass QASSextends Applet
{
publicfinalstaticint DELAY = 500;/* the thread delay is in milliseconds so we can see what happens */
private Thread thr;/* this thread runs the queen*/
publicvoid init ()
{
/* Labels and titles */
Label lblTitle =new Label ("A Knights Path", Label.CENTER);
lblTitle.setFont (new Font ("Arial", Font.BOLD, 25));
add (lblTitle);
Label lblTitle2 =new Label ("Press the button to Start", Label.CENTER);
lblTitle.setFont (new Font ("Arial", Font.BOLD, 10));
add (lblTitle2);
/*create a chessboard that draws lines as to where the queen has been on her travels*/
final ChessBoard chessbo =new ChessBoard (this);
add (chessbo);/* adds to the applet as we go */
/* This creates a button for the users to get the Queen to move */
final Choice ch =new Choice ();
ch.add ("");
ch.add ("");
/* creates a button so that the user can start the applet */
final Button btn =new Button ("Press here to make the Knight move");
// this creates the buttons action listener
ActionListener al;
al =new ActionListener ()
{
publicvoid actionPerformed (ActionEvent e)
{
Runnable r;
r =new Runnable ()
{
int [] boardPositions1 =
{
7, 47, 43, 27, 29, 21, 17, 57
/* i have an array list where the top left square is
/* position 1 and so on, flowing from left to right,
/* down to 64 in the bottom right square*/
};
publicvoid run ()
{
chessbo.reset ();
// thr != null is the check which stops the applet if the user moves away from the webpage it is on.
for (int i = 0; i < boardPositions1.length &&
thr !=null; i++)
{
chessbo.moveQueen (boardPositions1 [i]);
try
{
Thread.sleep (DELAY);
}
catch (InterruptedException e2)
{
}
}
ch.setEnabled (true);
btn.setEnabled (true);
}
};
ch.setEnabled (false);
btn.setEnabled (false);
thr =new Thread (r);
thr.start ();
}
};
btn.addActionListener (al);
// Add the Button object to the applet's Panel container.
add (btn);
}
// Stop the applet.
publicvoid stop ()
{
/* this Stops the applet if the page focus is lost */
thr =null;
}
}
finalclass ChessBoardextends Canvas
{
privatefinalstatic Color SQUARECOLOR =new Color (99, 99, 99);// Color of black squares in RGB notation
privatefinalstaticint SQUAREDIM = 30;// Chessboard Square Dimension
privatefinalstaticint BOARDDIM = 8 * SQUAREDIM + 2;// Chessboard Dimension which includes the black outline
privateint xboard;// Left coordinate of chessboard top-left corner
privateint yboard;// Top coordinate of chessboard top-left corner
privateint bwidth;// The board width
privateint bheight;// The board height
private Image imagebuffer;// Image buffer
private Graphics imGra;// Graphics context & image buffer
private Image imQueen;// Queen's image
privateint queenWidth;// Queen image width
privateint queenHeight;// Queen image height
private ArrayList trail;// Coordinates of the Queen's trail
privateint xcord;// right co-ordinate of queen origin (bottom right)
privateint ycord;// bottom co-ordinate of queen origin (bottom right)
// getImage and getDocumentBase methods are now called
Applet appl;
//this constructs chessbaord
ChessBoard (Applet appl)
{
bwidth = BOARDDIM+1;
bheight = BOARDDIM+1;
// centre the chessboard
xboard = (bwidth - BOARDDIM) / 2 + 1;
yboard = (bheight - BOARDDIM) / 2 + 1;
// makes sure image loads before its height and width are taken
MediaTracker mdtrac =new MediaTracker (this);
// Load queen's image.
imQueen = appl.getImage (appl.getDocumentBase (),"queentrans.gif");
mdtrac.addImage (imQueen, 0);
try
{
mdtrac.waitForID (0);
}
catch (InterruptedException e){}
// height and width are taken
queenWidth = imQueen.getWidth (appl);
queenHeight = imQueen.getHeight (appl);
xcord = xboard + (SQUAREDIM - queenWidth) / 2 + 1;
ycord = yboard + (SQUAREDIM - queenHeight) / 2 + 1;
// this holds the trail of the queen as she moves across the board
trail =new ArrayList ();
// Saves the applet reference for later use
this.appl = appl;
}
publicvoid addNotify ()
{
// creates canvas peer
super.addNotify ();
// Creates the image buffer.
imagebuffer = createImage (bwidth, bheight);
// Retrieve graphics context
imGra = imagebuffer.getGraphics ();
}
// This method is called when positioning the components
public Dimension getPreferredSize ()
{
returnnew Dimension (bwidth, bheight);
}
publicvoid moveQueen (int boardPosition)
{
int rebasedBoardPosition = boardPosition-1;
int col = rebasedBoardPosition % 8;
int row = rebasedBoardPosition / 8;
xcord = xboard + col * SQUAREDIM + (SQUAREDIM - queenWidth) / 2 + 1;
ycord = yboard + row * SQUAREDIM + (SQUAREDIM - queenHeight) / 2 + 1;
trail.add (new Point (xcord + queenWidth / 2, ycord + queenHeight / 2));
repaint ();
}
// chessboard and then queen are painted
publicvoid paint (Graphics graph)
{
// Paints the chessboard
paintChessBoard (imGra, xboard, yboard);
// Paints the queem
paintQueen (imGra, xcord, ycord);
// Paints the queen's trail behind her
paintTrail (imGra);
// Draws the contents of the image buffer
graph.drawImage (imagebuffer, 0, 0,this);
}
// Paints the chessboard (x, y) is the upper-left corner of the chess board
void paintChessBoard (Graphics graph,int x,int y)
{
// Paints the chessboard outline
graph.setColor (Color.black);
graph.drawRect (x, y, 8 * SQUAREDIM + 1, 8 * SQUAREDIM + 1);
// Paints the checks
for (int row = 0; row < 8; row++)
{
graph.setColor (((row & 1) != 0) ? SQUARECOLOR : Color.red);
for (int col = 0; col < 8; col++)
{
graph.fillRect (x + 1 + col * SQUAREDIM, y + 1 + row * SQUAREDIM,
SQUAREDIM, SQUAREDIM);
graph.setColor ((graph.getColor () == SQUARECOLOR) ? Color.red :
SQUARECOLOR);
}
}
}
// Paint the queen (x, y) is the upper-left corner of the chessboard
void paintQueen (Graphics graph,int x,int y)
{
graph.drawImage (imQueen, x, y, appl);
}
// Paint the queen's trail behind her
void paintTrail (Graphics graph)
{
graph.setColor (Color.black);
int len = trail.size ();
if (len == 0)
return;
Point poi = (Point) trail.get (0);
int xcord = poi.x;
int ycord = poi.y;
for (int i = 1; i < len; i++)
{
poi = (Point) trail.get (i);
graph.drawLine (xcord, ycord, poi.x, poi.y);
xcord = poi.x;
ycord = poi.y;
}
}
// clear the Array list to reset the applet
publicvoid reset ()
{
trail.clear ();
}
}
