Java Reference
In-Depth Information
import java.util.Observable;
import java.awt.*; // For Graphics
class SketchView extends JComponent implements Observer {
public void paint(Graphics g) {
// Temporary code
Graphics2D g2D = (Graphics2D)g; // Get a Java 2D device context
g2D.setPaint(Color.RED); // Draw in red
g2D.draw3DRect(50, 50, 150, 100, true); // Draw a raised 3D rectangle
g2D.drawString("A nice 3D rectangle", 60, 100); // Draw some text
}
// Rest of the class as before...
}
If you recompile the file
SketchFrame.java
and run Sketcher, you can see what the
paint()
method produces. You should see the window shown here.
OK, it's not your traditional meaning of 3D. In this case, the edges of the rectangle are highlighted so
that that they appear to be beveled and lift from the top left hand corner (or the coordinate origin).
How It Works
The graphics context is passed as the argument to the
paint()
method as type
Graphics
(the base
class for
Graphics2D)
so to use the methods defined in the
Graphics2D
class we must first cast it to
that type. The
paint()
method has a parameter type of
Graphics
for compatibility reasons.
Once we have cast the graphics context, we then set the color in which we will draw by calling the
setPaint()
method for the
Graphics2D
object and passing the drawing color as an argument. All
subsequent drawing operations will now be in
Color.RED
. We can change this again later with another
call to
setPaint()
when we want to draw in a different color.
Next we call the
draw3DRect()
method defined in the
Graphics2D
class that draws a 3D rectangle.
The first two arguments are integers specifying the
x
and
y
coordinates of the top-left corner of the
rectangle to be drawn, relative to the user space origin of the component - in this case the top-left
corner of the view object in the content pane. The third and fourth arguments are the width and height
of the rectangle respectively, also in user coordinates.
