stanford.androidlib.graphics

Class GPolygon

java.lang.Object

stanford.androidlib.graphics.GObject

stanford.androidlib.graphics.GPolygon

All Implemented Interfaces:

GFillable, GScalable

public class GPolygon
extends GObject
implements GFillable, GScalable

The GPolygon class is a graphical object whose appearance consists of a polygon.

Constructor Summary

Constructors

Constructor and Description
GPolygon() Constructs a new empty polygon at the origin.
GPolygon(float x, float y) Constructs a new empty polygon at (x, y).
GPolygon(GCanvas canvas) Constructs a new empty polygon at the origin.
GPolygon(GCanvas canvas, float x, float y) Constructs a new empty polygon at (x, y).
GPolygon(GCanvas canvas, GPoint[] points) Constructs a new polygon from the specified array of GPoint objects.
GPolygon(GPoint[] points) Constructs a new polygon from the specified array of GPoint objects.

Method Summary

Modifier and Type	Method and Description
GPolygon	addArc(float arcWidth, float arcHeight, float start, float sweep) Adds a series of edges to the polygon that simulates the arc specified by the parameters.
GPolygon	addEdge(float dx, float dy) Adds an edge to the polygon whose components are given by the displacements dx and dy from the last vertex.
GPolygon	addPolarEdge(float r, float theta) Adds an edge to the polygon specified in polar coordinates.
GPolygon	addVertex(float x, float y) Adds a vertex at (x, y) relative to the polygon origin.
protected GPolygon	clear() Calling this method deletes all vertices from the polygon and resets the scale and rotation factors to the their default values.
Object	clone() Overrides clone in Object to make sure that the vertex list is copied rather than shared.
boolean	contains(float x, float y) Checks to see whether a point is inside the object.
GRectangle	getBounds() Returns the bounding box of this object, which is defined to be the smallest rectangle that covers everything drawn by the figure.
GPoint	getCurrentPoint() Returns the coordinates of the last vertex added to the polygon, or null if the polygon is empty.
protected GPolygon	markAsComplete() Calling this method makes it illegal to add or remove vertices from the polygon.
void	paint(Canvas canvas) Implements the paint operation for this graphical object.
GPolygon	recenter() Recalculates the vertices of the polygon so that they are positioned relative to the geometric center of the object.
void	repaint() Overrides repaint in GObject to invalidate the cached polygon.
GPolygon	rotate(float theta) Rotates the polygon around its origin by the angle theta, measured in degrees.
GObject	scale(float sx, float sy) Scales the polygon by the scale factors sx and sy.

Methods inherited from class stanford.androidlib.graphics.GObject

addTo, addTo, addTo, contains, getBottomY, getCenterX, getCenterY, getColor, getFillColor, getGCanvas, getHeight, getLeftX, getLocation, getPaint, getRightX, getSize, getTopY, getWidth, getX, getY, intersects, isFilled, isVisible, moveBy, moveByPolar, moveTo, moveTo, moveTo, moveToPolar, remove, scale, sendBackward, sendForward, sendToBack, sendToFront, setBottomY, setBounds, setBounds, setBounds, setCanvas, setColor, setFillColor, setFilled, setGCanvas, setLocation, setLocation, setLocation, setPaint, setRightX, setSize, setSize, setVisible, setX, setY, toString, translate

Methods inherited from class java.lang.Object

equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

Methods inherited from interface stanford.androidlib.graphics.GFillable

getFillColor, isFilled, setFillColor, setFilled

Methods inherited from interface stanford.androidlib.graphics.GScalable

scale

Constructor Detail

GPolygon

public GPolygon()

Constructs a new empty polygon at the origin.

Usage:

GPolygon gpoly = new GPolygon();

GPolygon

public GPolygon(float x,
                float y)

Constructs a new empty polygon at (x, y).

Parameters:

x - The x-coordinate of the origin of the polygon

y - The y-coordinate of the origin of the polygon

Usage:

GPolygon gpoly = new GPolygon(x, y);

GPolygon

public GPolygon(GPoint[] points)

Constructs a new polygon from the specified array of GPoint objects. The polygon is automatically marked as complete.

Parameters:

points - An array of GPoint objects specifying the vertices

Usage:

GPolygon gpoly = new GPolygon(points);

GPolygon

public GPolygon(GCanvas canvas)

Constructs a new empty polygon at the origin.

Usage:

GPolygon gpoly = new GPolygon();

GPolygon

public GPolygon(GCanvas canvas,
                float x,
                float y)

Constructs a new empty polygon at (x, y).

Parameters:

x - The x-coordinate of the origin of the polygon

y - The y-coordinate of the origin of the polygon

Usage:

GPolygon gpoly = new GPolygon(x, y);

GPolygon

public GPolygon(GCanvas canvas,
                GPoint[] points)

Constructs a new polygon from the specified array of GPoint objects. The polygon is automatically marked as complete.

Parameters:

points - An array of GPoint objects specifying the vertices

Usage:

GPolygon gpoly = new GPolygon(points);

Method Detail

addVertex

public GPolygon addVertex(float x,
                          float y)

Adds a vertex at (x, y) relative to the polygon origin.

Parameters:

x - The x-coordinate of the vertex relative to the polygon origin

y - The y-coordinate of the vertex relative to the polygon origin

Usage:

gpoly.addVertex(x, y);

addEdge

public GPolygon addEdge(float dx,
                        float dy)

Adds an edge to the polygon whose components are given by the displacements dx and dy from the last vertex.

Parameters:

dx - The x displacement through which the edge moves

dy - The y displacement through which the edge moves

Usage:

gpoly.addEdge(dx, dy);

addPolarEdge

public final GPolygon addPolarEdge(float r,
                                   float theta)

Adds an edge to the polygon specified in polar coordinates. The length of the edge is given by r, and the edge extends in direction theta, measured in degrees counterclockwise from the +x axis.

Parameters:

r - The length of the edge

theta - The angle at which the edge extends measured in degrees

Usage:

gpoly.addPolarEdge(r, theta);

addArc

public GPolygon addArc(float arcWidth,
                       float arcHeight,
                       float start,
                       float sweep)

Adds a series of edges to the polygon that simulates the arc specified by the parameters. The x and y parameters for the arc bounding box are computed implicitly by figuring out what values would place the current vertex at the starting position.

Parameters:

arcWidth - The width of the oval from which the arc is taken

arcHeight - The height of the oval from which the arc is taken

start - The angle at which the arc begins

sweep - The extent of the arc

Usage:

gpoly.addArc(arcWidth, arcHeight, start, sweep);

getCurrentPoint

public GPoint getCurrentPoint()

Returns the coordinates of the last vertex added to the polygon, or null if the polygon is empty.

Returns:

The last vertex added to the polygon, or null if empty

Usage:

GPoint vertex = gpoly.getCurrentPoint();

scale

public GObject scale(float sx,
                     float sy)

Scales the polygon by the scale factors sx and sy.

Specified by:

scale in interface GScalable

Overrides:

scale in class GObject

Parameters:

sx - The factor used to scale all coordinates in the x direction

sy - The factor used to scale all coordinates in the y direction

Usage:

gpoly.scale(sx, sy);

rotate

public GPolygon rotate(float theta)

Rotates the polygon around its origin by the angle theta, measured in degrees.

Parameters:

theta - The angle of rotation in degrees counterclockwise

Usage:

gpoly.rotate(theta);

getBounds

public GRectangle getBounds()

Returns the bounding box of this object, which is defined to be the smallest rectangle that covers everything drawn by the figure.

Overrides:

getBounds in class GObject

Returns:

The bounding box for this object

Usage:

GRectangle bounds = gpoly.getBounds();

contains

public boolean contains(float x,
                        float y)

Checks to see whether a point is inside the object.

Overrides:

contains in class GObject

Parameters:

x - The x-coordinate of the point being tested

y - The y-coordinate of the point being tested

Returns:

true if the point (x, y) is inside the object, and false otherwise

Usage:

if (gpoly.contains(x, y)) . . .

paint

public void paint(Canvas canvas)

Implements the paint operation for this graphical object. This method is not called directly by clients.

Specified by:

paint in class GObject

Noshow:

recenter

public GPolygon recenter()

Recalculates the vertices of the polygon so that they are positioned relative to the geometric center of the object. This method allows clients to take a polygon drawn using mouse clicks on the screen and then to reformulate it so that it can be displayed relative to its center.

Usage:

gpoly.recenter();

clone

public Object clone()

Overrides clone in Object to make sure that the vertex list is copied rather than shared.

Overrides:

clone in class Object

Returns:

a clone of this instance.

See Also:

Cloneable

Noshow:

repaint

public void repaint()

Overrides repaint in GObject to invalidate the cached polygon.

Overrides:

repaint in class GObject

Noshow:

markAsComplete

protected GPolygon markAsComplete()

Calling this method makes it illegal to add or remove vertices from the polygon. Subclasses can invoke this method to protect the integrity of the structure from changes by the client.

clear

protected GPolygon clear()

Calling this method deletes all vertices from the polygon and resets the scale and rotation factors to the their default values. Subclasses can use this method to reconstruct a polygon.