Java Reference
In-Depth Information
public void
paint(Graphics g)
{
super
.paint(g);
Graphics2D g2 = (Graphics2D) g ;
g2 . setColor (Color .RED) ;
for
(Square r : squares)
{
r . draw(g2 , xImage , oImage) ;
}
}
...
The method is similar to the
paintComponent
method. However, since an applet is not
a
JPanel
,the
paint
method needs to be called. An object of type
JApplet
has a default
panel that does not need to be created. The
paint
method is called to draw on it. Our
implementation starts by clearing the window by calling
super.paint(g)
. Then we set the
brush color to red and we draw the squares. Note that it is the responsibility of each square
to display both its boarders and the image inside it (when present).
Next, let us examine the inner
MousePressed
class.
public class
TicTacToe
extends
JApplet
{
class
MyMouseListener
extends
MouseAdapter
{
public void
mousePressed (MouseEvent e )
{
for
(Square r : squares)
{
if
(r . contains(e. getPoint ()))
{
if
(! r . hasValue() )
{
r . placeCharacter(
'x'
);
repaint () ;
if
( isGameOver () )
{
return
;
computerMove () ;
repaint () ;
if
( isGameOver () )
{
return
;
}
}
}
}
}
}
...
}
The method iterates over all the squares of the board. The expression
e.getPoint()
returns the coordinates of where the mouse was pressed. If these coordinates are inside a
square, then we interpret this as the player trying to put an
X
in the square. Note that the
contains
method checks if a point is inside a rectangle. If the square already has value,
then we do not need to do anything. Otherwise, the program places an
X
in the square
and repaints the canvas. If the game is over, then the method terminates. Otherwise, the
computer makes a move and the program checks again if the game is over.
Next, let us start developing the logic of the
isGameOver
and
computerMove
methods.
The first method checks to see if there is a line by the player or the computer. The second
method determines the best possible move for the computer. We will start by creating
several auxiliary methods.
public boolean
isLine(
int
i,
int
j,
int
k,
char
c)
{
return
(squares . get( i ) . isCharacter(c)
