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(GPoint[] points) Constructs a new polygon from the specified array of GPoint objects.

Method Summary

Modifier and Type	Method and Description
void	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.
void	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.
void	addPolarEdge(float r, float theta) Adds an edge to the polygon specified in polar coordinates.
void	addVertex(float x, float y) Adds a vertex at (x, y) relative to the polygon origin.
protected void	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.
Paint	getFillColor() Returns the color used to display the filled region of this object.
boolean	isFilled() Returns whether this object is filled.
protected void	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.
void	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.
void	rotate(float theta) Rotates the polygon around its origin by the angle theta, measured in degrees.
void	scale(float sf) Scales the object on the screen by the scale factor sf, which applies in both dimensions.
void	scale(float sx, float sy) Scales the polygon by the scale factors sx and sy.
void	setFillColor(Paint color) Sets the color used to display the filled region of this object.
void	setFilled(boolean fill) Sets whether this object is filled.

Methods inherited from class stanford.androidlib.graphics.GObject

contains, getBottomY, getCenterX, getCenterY, getColor, getGCanvas, getHeight, getLocation, getPaint, getRightX, getSize, getWidth, getX, getY, intersects, isVisible, moveBy, moveByPolar, moveTo, moveTo, moveToPolar, sendBackward, sendForward, sendToBack, sendToFront, setBottomY, setCanvas, setColor, setGCanvas, setLocation, setLocation, setPaint, setRightX, setVisible, setX, setY, toString, translate

Methods inherited from class java.lang.Object

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

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);

Method Detail

addVertex

public void 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 void 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 void 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 void 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 void scale(float sx,
                  float sy)

Scales the polygon by the scale factors sx and sy.

Specified by:

scale in interface GScalable

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);

scale

public final void scale(float sf)

Scales the object on the screen by the scale factor sf, which applies in both dimensions.

Specified by:

scale in interface GScalable

Parameters:

sf - The factor used to scale all coordinates in both dimensions

Usage:

gobj.scale(sf);

rotate

public void 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);

setFilled

public void setFilled(boolean fill)

Sets whether this object is filled.

Specified by:

setFilled in interface GFillable

Parameters:

fill - true if the object should be filled, false for an outline

Usage:

gobj.setFilled(fill);

isFilled

public boolean isFilled()

Returns whether this object is filled.

Specified by:

isFilled in interface GFillable

Returns:

The color used to display the object

Usage:

if (gobj.isFilled()) . . .

setFillColor

public void setFillColor(Paint color)

Sets the color used to display the filled region of this object.

Specified by:

setFillColor in interface GFillable

Parameters:

color - The color used to display the filled region of this object

Usage:

gobj.setFillColor(color);

getFillColor

public Paint getFillColor()

Returns the color used to display the filled region of this object. If none has been set, getFillColor returns the color of the object.

Specified by:

getFillColor in interface GFillable

Returns:

The color used to display the filled region of this object

Usage:

Color color = gobj.getFillColor();

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 void 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 void 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 void 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.