Java Reference
In-Depth Information
This is large enough to accommodate our stars. If you
compile and run the applet, you should see the
AppletViewer
window shown here.
How It Works
The
Star
class has a
GeneralPath
object,
p
, as a member. The constructor sets the coordinates of the
start
point from the arguments, and calls the
createStar()
method that creates the path for the
star. The first line is drawn relative to the
start
point that is set by the call to
moveTo()
for
p
. For
each subsequent line, we retrieve the current position by calling
getCurrentPoint()
for
p
and
drawing the line relative to that. The last line to complete the star is drawn by calling
closePath()
.
We always need a
Shape
reference to draw a
Star
object, so we have included a
getShape()
method in the class that simply returns a reference to the current
GeneralPath
object as type
Shape
.
The
atLocation()
method recreates the path at the new position specified by the arguments and
returns a reference to it.
The
StarApplet
class draws stars on a component defined by the inner class
StarPane
. We draw the
stars using the
paint()
method for the
StarPane
object, which is a member of the
StarApplet
class. Each star is drawn in the nested loop with the position specified by (
x
,
y)
. The
y
coordinate
defines the vertical position of a row, so this is incremented by
delta
on each iteration of the outer
loop. The coordinate
x
is the position of a star within a row so this is incremented by
delta
on each
iteration of the inner loop.
Filling Shapes
Once you know how to create and draw a shape, filling it is easy. You just call the
fill()
method for
the
Graphics2D
object and pass a reference of type
Shape
to it. This works for any shape but for
sensible results the boundary should be closed.
Let's try it out by modifying the applet example that displayed stars.
Try It Out - Filling Stars
To fill the stars we just need to call the
fill()
method for each star in the
paint() m
ethod of the
StarPane
object. Modify the
paint()
method as follows:
public void paint(Graphics g) {
Graphics2D g2D = (Graphics2D)g;
Star star = new Star(0,0); // Create a star
