acm.graphics
Class GObject

java.lang.Object
  acm.graphics.GObject

Direct Known Subclasses:

GArc, GCompound, GImage, GLabel, GLine, GOval, GPen, GPolygon, GRect, GTurtle

public abstract class GObject
extends Object
implements Cloneable, Serializable

This class is the common superclass of all graphical objects that can be displayed on a GCanvas. Because it is an abstract class, you are not allowed to construct an object whose class is GObject directly. What you do instead is construct one of the concrete subclasses like GRect or GLine. The purpose of this class definition is to define methods that apply to all graphical objects regardless of their specific class.

The GObject class implements the Serializable interface by saving all of the internal state of the object. The parent, however, is saved only if the parent is a GCompound.

Method Summary

void	addActionListener(ActionListener listener) Adds an action listener to this graphical object.
void	addMouseListener(MouseListener listener) Adds a mouse listener to this graphical object.
void	addMouseMotionListener(MouseMotionListener listener) Adds a mouse motion listener to this graphical object.
boolean	contains(double x, double y) Checks to see whether a point is inside the object.
boolean	contains(GPoint pt) Checks to see whether a point is inside the object.
void	fireActionEvent(ActionEvent e) Triggers an action event for this graphical object.
void	fireActionEvent(String actionCommand) Triggers an action event for this graphical object with the specified action command.
GRectangle	getBounds() Returns the bounding box of this object, which is defined to be the smallest rectangle that covers everything drawn by the figure.
Color	getColor() Returns the color used to display this object.
double	getHeight() Returns the height of this object, which is defined to be the height of the bounding box.
GPoint	getLocation() Returns the location of this object as a GPoint.
GContainer	getParent() Returns the parent of this object, which is the canvas or compound object in which it is enclosed.
GDimension	getSize() Returns the size of the bounding box for this object.
double	getWidth() Returns the width of this object, which is defined to be the width of the bounding box.
double	getX() Returns the x-coordinate of the object.
double	getY() Returns the y-coordinate of the object.
boolean	isVisible() Checks to see whether this object is visible.
void	move(double dx, double dy) Moves the object on the screen using the displacements dx and dy.
void	movePolar(double r, double theta) Moves the object using displacements given in polar coordinates.
void	paint(Graphics g) All subclasses of GObject must define a paint method which allows the object to draw itself on the Graphics context passed in as the parameter g.
void	pause(double milliseconds) Delays the calling thread for the specified time, which is expressed in milliseconds.
void	removeActionListener(ActionListener listener) Removes an action listener from this graphical object.
void	removeMouseListener(MouseListener listener) Removes a mouse listener from this graphical object.
void	removeMouseMotionListener(MouseMotionListener listener) Removes a mouse motion listener from this graphical object.
void	sendBackward() Moves this object one step toward the back in the z dimension.
void	sendForward() Moves this object one step toward the front in the z dimension.
void	sendToBack() Moves this object to the back of the display in the z dimension.
void	sendToFront() Moves this object to the front of the display in the z dimension.
void	setColor(Color color) Sets the color used to display this object.
void	setLocation(double x, double y) Sets the location of this object to the point (x, y).
void	setVisible(boolean visible) Sets whether this object is visible.

Method Detail

public void addActionListener(ActionListener listener)

Adds an action listener to this graphical object.

Usage:

gobj.addActionListener(listener);

Parameter:

listener

Any object that implements the ActionListener interface

public void addMouseListener(MouseListener listener)

Adds a mouse listener to this graphical object.

Usage:

gobj.addMouseListener(listener);

Parameter:

listener

Any object that implements the MouseListener interface

public void addMouseMotionListener(MouseMotionListener listener)

Adds a mouse motion listener to this graphical object.

Usage:

gobj.addMouseMotionListener(listener);

Parameter:

listener

Any object that implements the MouseMotionListener interface

public boolean contains(double x, double y)

Checks to see whether a point is inside the object. By default, this method simply checks to see if the point is inside the bounding box. Many subclasses will need to override this to check whether the point is contained in the shape.

Usage:

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

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

public final boolean contains(GPoint pt)

Checks to see whether a point is inside the object.

Usage:

if (gobj.contains(pt)) . . .

Parameter:

pt	The point being tested

Returns:

true if the point is inside the object, and false otherwise

public void fireActionEvent(ActionEvent e)

Triggers an action event for this graphical object.

Usage:

gobj.fireActionEvent(e);

Parameter:

e	The ActionEvent to fire

public void fireActionEvent(String actionCommand)

Triggers an action event for this graphical object with the specified action command.

Usage:

gobj.fireActionEvent(actionCommand);

Parameter:

actionCommand

The action command to include in the event

public abstract GRectangle getBounds()

Returns the bounding box of this object, which is defined to be the smallest rectangle that covers everything drawn by the figure. The coordinates of this rectangle do not necessarily match the location returned by getLocation. Given a GLabel object, for example, getLocation returns the coordinates of the point on the baseline at which the string begins; getBounds, by contrast, returns a rectangle that covers the entire window area occupied by the string.

Usage:	GRectangle bounds = gobj.getBounds();
Returns:	The bounding box for this object

public Color getColor()

Returns the color used to display this object.

Usage:	Color color = gobj.getColor();
Returns:	The color used to display this object

public double getHeight()

Returns the height of this object, which is defined to be the height of the bounding box.

Usage:	double height = gobj.getHeight();
Returns:	The height of this object on the screen

public GPoint getLocation()

Returns the location of this object as a GPoint.

Usage:	GPoint pt = gobj.getLocation();
Returns:	The location of this object as a GPoint

public GContainer getParent()

Returns the parent of this object, which is the canvas or compound object in which it is enclosed.

Usage:	GContainer parent = gobj.getParent();
Returns:	The parent of this object

public GDimension getSize()

Returns the size of the bounding box for this object.

Usage:	GDimension size = gobj.getSize();
Returns:	The size of this object

public double getWidth()

Returns the width of this object, which is defined to be the width of the bounding box.

Usage:	double width = gobj.getWidth();
Returns:	The width of this object on the screen

public double getX()

Returns the x-coordinate of the object.

Usage:	double x = gobj.getX();
Returns:	The x-coordinate of the object

public double getY()

Returns the y-coordinate of the object.

Usage:	double y = gobj.getY();
Returns:	The y-coordinate of the object

public boolean isVisible()

Checks to see whether this object is visible.

Usage:	if (gobj.isVisible()) . . .
Returns:	true if the object is visible, otherwise false

public void move(double dx, double dy)

Moves the object on the screen using the displacements dx and dy.

Usage:

gobj.move(dx, dy);

Parameters:

dx	The distance to move the object in the x direction (positive is rightward)
dy	The distance to move the object in the y direction (positive is downward)

public final void movePolar(double r, double theta)

Moves the object using displacements given in polar coordinates. The parameter r specifies the distance to move and theta specifies the angle in which the motion occurs. The angle is measured in degrees increasing counterclockwise from the +x axis.

Usage:

gobj.movePolar(r, theta);

Parameters:

r	The distance to move
theta	The angle in which to move, measured in degrees increasing counterclockwise from the +x axis

public abstract void paint(Graphics g)

All subclasses of GObject must define a paint method which allows the object to draw itself on the Graphics context passed in as the parameter g.

Usage:

gobj.paint(g);

Parameter:

g	The graphics context into which the painting is done

public void pause(double milliseconds)

Delays the calling thread for the specified time, which is expressed in milliseconds. Unlike Thread.sleep, this method never throws an exception.

Usage:

gobj.pause(milliseconds);

Parameter:

milliseconds

The sleep time in milliseconds

public void removeActionListener(ActionListener listener)

Removes an action listener from this graphical object.

Usage:

gobj.removeActionListener(listener);

Parameter:

listener

The listener object to remove

public void removeMouseListener(MouseListener listener)

Removes a mouse listener from this graphical object.

Usage:

gobj.removeMouseListener(listener);

Parameter:

listener

The listener object to remove

public void removeMouseMotionListener(MouseMotionListener listener)

Removes a mouse motion listener from this graphical object.

Usage:

gobj.removeMouseMotionListener(listener);

Parameter:

listener

The listener object to remove

public void sendBackward()

Moves this object one step toward the back in the z dimension. If it was already at the back of the stack, nothing happens.

Usage:

gobj.sendBackward();

public void sendForward()

Moves this object one step toward the front in the z dimension. If it was already at the front of the stack, nothing happens.

Usage:

gobj.sendForward();

public void sendToBack()

Moves this object to the back of the display in the z dimension. By moving it to the back, this object will appear to be behind the other graphical objects on the display and may be obscured by other objects in front.

Usage:

gobj.sendToBack();

public void sendToFront()

Moves this object to the front of the display in the z dimension. By moving it to the front, this object will appear to be on top of the other graphical objects on the display and may hide any objects that are further back.

Usage:

gobj.sendToFront();

public void setColor(Color color)

Sets the color used to display this object.

Usage:

gobj.setColor(color);

Parameter:

color

The color used to display this object

public void setLocation(double x, double y)

Sets the location of this object to the point (x, y).

Usage:

gobj.setLocation(x, y);

Parameters:

x	The new x-coordinate for the object
y	The new y-coordinate for the object

public void setVisible(boolean visible)

Sets whether this object is visible.

Usage:

gobj.setVisible(visible);

Parameter:

visible

true to make the object visible, false to hide it