com.brunchboy.util.swing.relativelayout
Class AttributeType

java.lang.Object
  |
  +--com.brunchboy.util.swing.relativelayout.AttributeType

public abstract class AttributeType

extends Object

A typesafe enumeration of the types of attributes that can be associated with components within a RelativeLayout. This class is immutable, and thus may be safely shared without concern for threading behavior.

This is an abstract class; there is a concrete subclass for each defined attribute type. The concrete subclasses know how to derive their own value from other available attributes. This refinement is an illustration of how typesafe enumerations can grow into full-fledged, polymorphic tools.

Version:

$Id: AttributeType.java,v 1.2 2002/08/16 05:13:04 jim Exp $

Author:

James Elliott, jim@brunchboy.com

Field Summary

static AttributeType	BOTTOM Attribute type representing the bottom edge of a component.
static AttributeType	HEIGHT Attribute type representing the height of a component.
static AttributeType	HORIZONTAL_CENTER Attribute type representing the horizontal center of a component.
static AttributeType	LEFT Attribute type representing the left edge of a component.
static AttributeType	RIGHT Attribute type representing the right edge of a component.
static AttributeType	TOP Attribute type representing the top edge of a component.
static String	VERSION Provides access to the CVS version of this class.
static AttributeType	VERTICAL_CENTER Attribute type representing the vertical center of a component.
static AttributeType	WIDTH Attribute type representing the width of a component.

Constructor Summary

protected

AttributeType(String name, AttributeAxis axis) Protected constructor prevents instantiation of this class.

Method Summary

abstract int	deriveValue(ComponentSpecifications specs, boolean minimumSize) Compute the value of this attribute given other attributes from which it can be derived.
static Set	getAllTypes() Return the set of all known attribute types.
AttributeAxis	getAxis() Return the axis on which this attribute type is defined.
static Set	getAxisTypes(AttributeAxis axis) Return the set of attribute types associated with an axis.
static AttributeType	getInstance(String name) Static factory that looks up an attribute type by name.
String	getName() Return name of this attribute type.
String	toString() Provide a textual representation of the attribute type for debugging purposes.

Methods inherited from class java.lang.Object

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

Field Detail

VERSION

public static final String VERSION

Provides access to the CVS version of this class.

See Also:

Constant Field Values

LEFT

public static final AttributeType LEFT

Attribute type representing the left edge of a component.

RIGHT

public static final AttributeType RIGHT

Attribute type representing the right edge of a component.

HORIZONTAL_CENTER

public static final AttributeType HORIZONTAL_CENTER

Attribute type representing the horizontal center of a component.

WIDTH

public static final AttributeType WIDTH

Attribute type representing the width of a component.

TOP

public static final AttributeType TOP

Attribute type representing the top edge of a component.

BOTTOM

public static final AttributeType BOTTOM

Attribute type representing the bottom edge of a component.

VERTICAL_CENTER

public static final AttributeType VERTICAL_CENTER

Attribute type representing the vertical center of a component.

HEIGHT

public static final AttributeType HEIGHT

Attribute type representing the height of a component.

Constructor Detail

AttributeType

protected AttributeType(String name,
                        AttributeAxis axis)

Protected constructor prevents instantiation of this class. Also builds the sets per-Axis attributes at class-load time.

Parameters:

name - the name of the attribute type to create.

axis - the axis on which this attribute type is defined.

Throws:

NullPointerException - if either parameter is null.

Method Detail

getName

public String getName()

Return name of this attribute type.

Returns:

the name by which this type is known.

getAxis

public AttributeAxis getAxis()

Return the axis on which this attribute type is defined.

Returns:

the axis affected by this attribute type.

getInstance

public static AttributeType getInstance(String name)

Static factory that looks up an attribute type by name.

Parameters:

name - the name of the desired attribute type.

Returns:

the corresponding instance.

Throws:

NoSuchElementException - if the desired instance doesn't exist.

deriveValue

public abstract int deriveValue(ComponentSpecifications specs,
                                boolean minimumSize)

Compute the value of this attribute given other attributes from which it can be derived. Concrete subclasses must implement this method.

Parameters:

specs - source of other attributes for deriving this value.

minimumSize - indicates whether, should we need to query the component itself for sizing information, we should ask for the minimum size as opposed to the preferred size.

Returns:

the derived value, if possible.

Throws:

IllegalStateException - if there are not enough values from which to derive ours.

getAllTypes

public static Set getAllTypes()

Return the set of all known attribute types.

Returns:

the attributes which exist; these are the only instances of this class which will ever exist. Cannot be modified.

getAxisTypes

public static Set getAxisTypes(AttributeAxis axis)

Return the set of attribute types associated with an axis.

Parameters:

axis - the axis of interest.

Returns:

the attribute types which are defined on that axis. May be empty, but will never be null. Cannot be modified.

toString

public String toString()

Provide a textual representation of the attribute type for debugging purposes.

Overrides:

toString in class Object

Returns:

the description of this attribute type.