You have already learned how to draw most of shapes represented in the java.awt.geom
package. To create more complicated geometry, such as polygons, polylines, or stars you use another class from this package, GeneralPath
.
This class implements the
Shape
interface and represents a geometric path constructed from lines, and quadratic and cubic curves. The three constructors in this class can create the
GeneralPath
object with the default winding rule (WIND_NON_ZERO
), the given winding rule (WIND_NON_ZERO
or WIND_EVEN_ODD
), or the specified initial coordinate capacity. The winding rule specifies how the interior of a path is determined.
public void Paint (Graphics g) { Graphics2D g2 = (Graphics2D) g; ... }
To create an empty GeneralPath
instance call new GeneralPath()
and then add segments to the shape by using the following methods:
moveTo(float x, float y)
– Moves the current point of the path to the given pointlineTo(float x, float y)
– Adds a line segment to the current pathquadTo(float ctrlx, float ctrly, float x2, floaty2)
– Adds a quadratic curve segment to the current pathcurveTo(float ctrlx1, float ctrly1, float ctrlx2, float ctrly2, float x3, floaty3)
– Adds a cubic curve segment to the current pathclosePath()
– Closes the current pathThe following example illustrates how to draw a polyline by using GeneralPath
:
// draw GeneralPath (polyline) int x2Points[] = {0, 100, 0, 100}; int y2Points[] = {0, 50, 50, 0}; GeneralPath polyline = new GeneralPath(GeneralPath.WIND_EVEN_ODD, x2Points.length); polyline.moveTo (x2Points[0], y2Points[0]); for (int index = 1; index < x2Points.length; index++) { polyline.lineTo(x2Points[index], y2Points[index]); }; g2.draw(polyline); |
This example illustrates how to draw a polygon by using GeneralPath
:
// draw GeneralPath (polygon) int x1Points[] = {0, 100, 0, 100}; int y1Points[] = {0, 50, 50, 0}; GeneralPath polygon = new GeneralPath(GeneralPath.WIND_EVEN_ODD, x1Points.length); polygon.moveTo(x1Points[0], y1Points[0]); for (int index = 1; index < x1Points.length; index++) { polygon.lineTo(x1Points[index], y1Points[index]); }; polygon.closePath(); g2.draw(polygon); |
Note that the only difference between two last code examples is the closePath()
method. This method makes a polygon from a polyline by drawing a straight line back to the coordinates of the last moveTo
.
To add a specific path to the end of your GeneralPath
object you use one of the append()
methods. The
ShapesDemo2D.java
code example contains additional implementations of arbitrary shapes.