12.3 Drawing and Filling Shapes

Example 12-6 lists a GraphicsExample implementation that shows how various Shape objects can be defined, drawn, and filled. The example produces the output shown in Figure 12-4. Although the Java 2D API allows basic shapes to be drawn and filled using the methods demonstrated in Example 12-1, this example uses a different approach. It defines each shape as a Shape object, using various classes, mostly from java.awt.geom.

Each Shape is drawn using the draw( ) method of the Graphics2D class and filled using the fill( ) method. Note that each Shape object is defined with one corner at (or near) the origin, rather than at the location where it is displayed on the screen. This creates position-independent objects that can easily be reused. To draw the shapes at particular locations, the example uses the translate( ) method of Graphics2D to move the origin of the coordinate system. Finally, the call to setStroke( ) specifies that drawing be done with a two-pixel-wide line, while the call to setRenderingHint( ) requests that drawing be done using antialiasing.

Figure 12-4. Drawing and filling shapes with the Java 2D API

Example 12-6. Shapes.java

package je3.graphics;
import java.awt.*;
import java.awt.geom.*;
import java.awt.font.*;
import java.awt.image.*;

/** A demonstration of Java2D shapes */
public class Shapes implements GraphicsExample {
    static final int WIDTH = 725, HEIGHT = 250;    // Size of our example
    public String getName( ) {return "Shapes";}     // From GraphicsExample
    public int getWidth( ) { return WIDTH; }        // From GraphicsExample
    public int getHeight( ) { return HEIGHT; }      // From GraphicsExample

    Shape[  ] shapes = new Shape[  ] {
        // A straight line segment
        new Line2D.Float(0, 0, 100, 100),
        // A quadratic bezier curve.  Two end points and one control point
        new QuadCurve2D.Float(0, 0, 80, 15, 100, 100),
        // A cubic bezier curve.  Two end points and two control points
        new CubicCurve2D.Float(0, 0, 80, 15, 10, 90, 100, 100),
        // A 120 degree portion of an ellipse
        new Arc2D.Float(-30, 0, 100, 100, 60, -120, Arc2D.OPEN),
        // A 120 degree portion of an ellipse, closed with a chord
        new Arc2D.Float(-30, 0, 100, 100, 60, -120, Arc2D.CHORD),
        // A 120 degree pie slice of an ellipse
        new Arc2D.Float(-30, 0, 100, 100, 60, -120, Arc2D.PIE),
        // An ellipse
        new Ellipse2D.Float(0, 20, 100, 60),
        // A rectangle
        new Rectangle2D.Float(0, 20, 100, 60),
        // A rectangle with rounded corners
        new RoundRectangle2D.Float(0, 20, 100, 60, 15, 15),
        // A triangle
        new Polygon(new int[  ] { 0, 0, 100 }, new int[  ] {20, 80, 80}, 3),
        // A random polygon, initialized in code below
        null,
        // A spiral: an instance of a custom Shape implementation
        new Spiral(50, 50, 5, 0, 50, 4*Math.PI),
    };

    {   // Initialize the null shape above as a Polygon with random points
        Polygon p = new Polygon( );
        for(int i = 0; i < 10; i++) 
            p.addPoint((int)(100*Math.random( )), (int)(100*Math.random( )));
        shapes[10] = p;
    }

    // These are the labels for each of the shapes 
    String[  ] labels = new String[  ] {
        "Line2D", "QuadCurve2D", "CubicCurve2D", "Arc2D (OPEN)",
        "Arc2D (CHORD)", "Arc2D (PIE)", "Ellipse2D", "Rectangle2D",
        "RoundRectangle2D", "Polygon", "Polygon (random)", "Spiral"
    };

    /** Draw the example */
    public void draw(Graphics2D g, Component c) {
        // Set basic drawing attributes
        g.setFont(new Font("SansSerif", Font.PLAIN, 10));      // select font
        g.setStroke(new BasicStroke(2.0f));                    // 2 pixel lines
        g.setRenderingHint(RenderingHints.KEY_ANTIALIASING,    // antialiasing
                           RenderingHints.VALUE_ANTIALIAS_ON);
        g.translate(10, 10);                                   // margins

        // Loop through each shape
        for(int i = 0; i < shapes.length; i++) {
            g.setColor(Color.yellow);            // Set a color
            g.fill(shapes[i]);                   // Fill the shape with it
            g.setColor(Color.black);             // Switch to black
            g.draw(shapes[i]);                   // Outline the shape with it
            g.drawString(labels[i], 0, 110);     // Label the shape
            g.translate(120, 0);                 // Move over for next shape
            if (i % 6  == 5) g.translate(-6*120, 120);  // Move down after 6
        }
    }
}