AccessibleContext represents the minimum information all accessible objects
return. This information includes the accessible name, description, role,
and state of the object, as well as information about its parent and
children. AccessibleContext also contains methods for
obtaining more specific accessibility information about a component.
If the component supports them, these methods will return an object that
implements one or more of the following interfaces:
- AccessibleAction
- the object can perform one or more actions.
This interface provides the standard mechanism for an assistive
technology to determine what those actions are and tell the object
to perform them. Any object that can be manipulated should
support this interface.
- AccessibleComponent
- the object has a graphical representation.
This interface provides the standard mechanism for an assistive
technology to determine and set the graphical representation of the
object. Any object that is rendered on the screen should support
this interface.
- AccessibleSelection
- the object allows its children to be
selected. This interface provides the standard mechanism for an
assistive technology to determine the currently selected children of the object
as well as modify its selection set. Any object that has children
that can be selected should support this interface.
- AccessibleText
- the object presents editable textual information
on the display. This interface provides the standard mechanism for
an assistive technology to access that text via its content, attributes,
and spatial location. Any object that contains editable text should
support this interface.
- AccessibleValue
- the object supports a numerical value. This
interface provides the standard mechanism for an assistive technology
to determine and set the current value of the object, as well as obtain its
minimum and maximum values. Any object that supports a numerical value
should support this interface.
Constant used to indicate that the supported set of actions
has changed. The old value in the PropertyChangeEvent will
be an Integer representing the old number of actions supported
and the new value will be an Integer representing the new
number of actions supported.
Constant used to determine when the active descendant of a component
has changed. The active descendant is used for objects such as
list, tree, and table, which may have transient children. When the
active descendant has changed, the old value of the property change
event will be the Accessible representing the previous active child, and
the new value will be the Accessible representing the current active
child.
Constant used to determine when the accessibleText caret has changed.
The old value in the PropertyChangeEvent will be an
integer representing the old caret position, and the new value will
be an integer representing the new/current caret position.
Constant used to determine when Accessible children are added/removed
from the object. If an Accessible child is being added, the old
value will be null and the new value will be the Accessible child. If an
Accessible child is being removed, the old value will be the Accessible
child, and the new value will be null.
PropertyChangeEvent which indicates that a change has occurred
in a component's bounds.
The oldValue is the old component bounds and the newValue is
the new component bounds.
Constant used to determine when the accessibleDescription property has
changed. The old value in the PropertyChangeEvent will be the
old accessibleDescription and the new value will be the new
accessibleDescription.
Constant used to indicate that a hypertext element has received focus.
The old value in the PropertyChangeEvent will be an Integer
representing the start index in the document of the previous element
that had focus and the new value will be an Integer representing
the start index in the document of the current element that has
focus. A value of -1 indicates that an element does not or did
not have focus.
PropertyChangeEvent which indicates that a significant change
has occurred to the children of a component like a tree or text.
This change notifies the event listener that it needs to
reacquire the state of the subcomponents. The oldValue is
null and the newValue is the component whose children have
become invalid.
Constant used to determine when the accessibleName property has
changed. The old value in the PropertyChangeEvent will be the old
accessibleName and the new value will be the new accessibleName.
Constant used to determine when the accessibleSelection has changed.
The old and new values in the PropertyChangeEvent are currently
reserved for future use.
Constant used to determine when the accessibleStateSet property has
changed. The old value will be the old AccessibleState and the new
value will be the new AccessibleState in the accessibleStateSet.
For example, if a component that supports the vertical and horizontal
states changes its orientation from vertical to horizontal, the old
value will be AccessibleState.VERTICAL and the new value will be
AccessibleState.HORIZONTAL. Please note that either value can also
be null. For example, when a component changes from being enabled
to disabled, the old value will be AccessibleState.ENABLED
and the new value will be null.
Constant used to indicate that the table caption has changed
The old value in the PropertyChangeEvent will be an Accessible
representing the previous table caption and the new value will
be an Accessible representing the new table caption.
Constant used to indicate that the column description has changed
The old value in the PropertyChangeEvent will be null and the
new value will be an Integer representing the column index.
Constant used to indicate that the column header has changed
The old value in the PropertyChangeEvent will be null and the
new value will be an AccessibleTableModelChange representing
the header change.
Constant used to indicate that table data has changed.
The old value in the PropertyChangeEvent will be null and the
new value will be an AccessibleTableModelChange representing
the table change.
Constant used to indicate that the row description has changed
The old value in the PropertyChangeEvent will be null and the
new value will be an Integer representing the row index.
Constant used to indicate that the row header has changed
The old value in the PropertyChangeEvent will be null and the
new value will be an AccessibleTableModelChange representing
the header change.
Constant used to indicate that the table summary has changed
The old value in the PropertyChangeEvent will be an Accessible
representing the previous table summary and the new value will
be an Accessible representing the new table summary.
PropertyChangeEvent which indicates that text attributes have changed.
For attribute insertion, the oldValue is null and the newValue
is an AccessibleAttributeSequence specifying the attributes that were
inserted.
For attribute deletion, the oldValue is an AccessibleAttributeSequence
specifying the attributes that were deleted and the newValue is null.
For attribute replacement, the oldValue is an AccessibleAttributeSequence
specifying the old attributes and the newValue is an
AccessibleAttributeSequence specifying the new attributes.
PropertyChangeEvent which indicates that text has changed.
For text insertion, the oldValue is null and the newValue
is an AccessibleTextSequence specifying the text that was
inserted.
For text deletion, the oldValue is an AccessibleTextSequence
specifying the text that was deleted and the newValue is null.
For text replacement, the oldValue is an AccessibleTextSequence
specifying the old text and the newValue is an AccessibleTextSequence
specifying the new text.
Constant used to determine when the accessibleValue property has
changed. The old value in the PropertyChangeEvent will be a Number
representing the old value and the new value will be a Number
representing the new value
Constant used to determine when the visual appearance of the object
has changed. The old and new values in the PropertyChangeEvent are
currently reserved for future use.
Adds a PropertyChangeListener to the listener list.
The listener is registered for all Accessible properties and will
be called when those properties change.
Indicates whether some other object is "equal to" this one.
The equals
method implements an equivalence relation
on non-null object references:
- It is reflexive: for any non-null reference value
x
, x.equals(x)
should return
true
.
- It is symmetric: for any non-null reference values
x
and y
, x.equals(y)
should return true
if and only if
y.equals(x)
returns true
.
- It is transitive: for any non-null reference values
x
, y
, and z
, if
x.equals(y)
returns true
and
y.equals(z)
returns true
, then
x.equals(z)
should return true
.
- It is consistent: for any non-null reference values
x
and y
, multiple invocations of
x.equals(y) consistently return true
or consistently return false
, provided no
information used in equals
comparisons on the
objects is modified.
- For any non-null reference value
x
,
x.equals(null)
should return false
.
The equals method for class Object
implements
the most discriminating possible equivalence relation on objects;
that is, for any non-null reference values x
and
y
, this method returns true
if and only
if x
and y
refer to the same object
(x == y
has the value true
).
Note that it is generally necessary to override the hashCode
method whenever this method is overridden, so as to maintain the
general contract for the hashCode method, which states
that equal objects must have equal hash codes.
Support for reporting bound property changes. If oldValue and
newValue are not equal and the PropertyChangeEvent listener list
is not empty, then fire a PropertyChange event to each listener.
In general, this is for use by the Accessible objects themselves
and should not be called by an application program.
Gets the AccessibleAction associated with this object that supports
one or more actions.
Returns the specified Accessible child of the object. The Accessible
children of an Accessible object are zero-based, so the first child
of an Accessible child is at index 0, the second child is at index 1,
and so on.
Returns the number of accessible children of the object.
Gets the AccessibleComponent associated with this object that has a
graphical representation.
Gets the accessibleDescription property of this object. The
accessibleDescription property of this object is a short localized
phrase describing the purpose of the object. For example, in the
case of a 'Cancel' button, the accessibleDescription could be
'Ignore changes and close dialog box.'
Gets the AccessibleEditableText associated with this object
presenting editable text on the display.
Gets the AccessibleIcons associated with an object that has
one or more associated icons
Gets the 0-based index of this object in its accessible parent.
Gets the accessibleName property of this object. The accessibleName
property of an object is a localized String that designates the purpose
of the object. For example, the accessibleName property of a label
or button might be the text of the label or button itself. In the
case of an object that doesn't display its name, the accessibleName
should still be set. For example, in the case of a text field used
to enter the name of a city, the accessibleName for the en_US locale
could be 'city.'
Gets the Accessible parent of this object.
Gets the AccessibleRelationSet associated with an object
Gets the role of this object. The role of the object is the generic
purpose or use of the class of this object. For example, the role
of a push button is AccessibleRole.PUSH_BUTTON. The roles in
AccessibleRole are provided so component developers can pick from
a set of predefined roles. This enables assistive technologies to
provide a consistent interface to various tweaked subclasses of
components (e.g., use AccessibleRole.PUSH_BUTTON for all components
that act like a push button) as well as distinguish between sublasses
that behave differently (e.g., AccessibleRole.CHECK_BOX for check boxes
and AccessibleRole.RADIO_BUTTON for radio buttons).
Note that the AccessibleRole class is also extensible, so
custom component developers can define their own AccessibleRole's
if the set of predefined roles is inadequate.
Gets the AccessibleSelection associated with this object which allows its
Accessible children to be selected.
Gets the state set of this object. The AccessibleStateSet of an object
is composed of a set of unique AccessibleStates. A change in the
AccessibleStateSet of an object will cause a PropertyChangeEvent to
be fired for the ACCESSIBLE_STATE_PROPERTY property.
Gets the AccessibleTable associated with an object
Gets the AccessibleText associated with this object presenting
text on the display.
Gets the AccessibleValue associated with this object that supports a
Numerical value.
Returns the runtime class of an object. That Class
object is the object that is locked by static synchronized
methods of the represented class.
Gets the locale of the component. If the component does not have a
locale, then the locale of its parent is returned.
Returns a hash code value for the object. This method is
supported for the benefit of hashtables such as those provided by
java.util.Hashtable
.
The general contract of hashCode
is:
- Whenever it is invoked on the same object more than once during
an execution of a Java application, the hashCode method
must consistently return the same integer, provided no information
used in equals comparisons on the object is modified.
This integer need not remain consistent from one execution of an
application to another execution of the same application.
- If two objects are equal according to the equals(Object)
method, then calling the
hashCode
method on each of
the two objects must produce the same integer result.
- It is not required that if two objects are unequal
according to the
method, then calling the hashCode method on each of the
two objects must produce distinct integer results. However, the
programmer should be aware that producing distinct integer results
for unequal objects may improve the performance of hashtables.
As much as is reasonably practical, the hashCode method defined by
class Object does return distinct integers for distinct
objects. (This is typically implemented by converting the internal
address of the object into an integer, but this implementation
technique is not required by the
JavaTM programming language.)
Wakes up a single thread that is waiting on this object's
monitor. If any threads are waiting on this object, one of them
is chosen to be awakened. The choice is arbitrary and occurs at
the discretion of the implementation. A thread waits on an object's
monitor by calling one of the
wait
methods.
The awakened thread will not be able to proceed until the current
thread relinquishes the lock on this object. The awakened thread will
compete in the usual manner with any other threads that might be
actively competing to synchronize on this object; for example, the
awakened thread enjoys no reliable privilege or disadvantage in being
the next thread to lock this object.
This method should only be called by a thread that is the owner
of this object's monitor. A thread becomes the owner of the
object's monitor in one of three ways:
- By executing a synchronized instance method of that object.
- By executing the body of a
synchronized
statement
that synchronizes on the object.
- For objects of type
Class,
by executing a
synchronized static method of that class.
Only one thread at a time can own an object's monitor.
Wakes up all threads that are waiting on this object's monitor. A
thread waits on an object's monitor by calling one of the
wait
methods.
The awakened threads will not be able to proceed until the current
thread relinquishes the lock on this object. The awakened threads
will compete in the usual manner with any other threads that might
be actively competing to synchronize on this object; for example,
the awakened threads enjoy no reliable privilege or disadvantage in
being the next thread to lock this object.
This method should only be called by a thread that is the owner
of this object's monitor. See the notify
method for a
description of the ways in which a thread can become the owner of
a monitor.
Removes a PropertyChangeListener from the listener list.
This removes a PropertyChangeListener that was registered
for all properties.
Sets the accessible description of this object. Changing the
name will cause a PropertyChangeEvent to be fired for the
ACCESSIBLE_DESCRIPTION_PROPERTY property.
Sets the localized accessible name of this object. Changing the
name will cause a PropertyChangeEvent to be fired for the
ACCESSIBLE_NAME_PROPERTY property.
Sets the Accessible parent of this object. This is meant to be used
only in the situations where the actual component's parent should
not be treated as the component's accessible parent and is a method
that should only be called by the parent of the accessible child.
Returns a string representation of the object. In general, the
toString
method returns a string that
"textually represents" this object. The result should
be a concise but informative representation that is easy for a
person to read.
It is recommended that all subclasses override this method.
The toString
method for class Object
returns a string consisting of the name of the class of which the
object is an instance, the at-sign character `@
', and
the unsigned hexadecimal representation of the hash code of the
object. In other words, this method returns a string equal to the
value of:
getClass().getName() + '@' + Integer.toHexString(hashCode())
Causes current thread to wait until another thread invokes the
method or the
method for this object.
In other words, this method behaves exactly as if it simply
performs the call
wait(0).
The current thread must own this object's monitor. The thread
releases ownership of this monitor and waits until another thread
notifies threads waiting on this object's monitor to wake up
either through a call to the notify
method or the
notifyAll
method. The thread then waits until it can
re-obtain ownership of the monitor and resumes execution.
As in the one argument version, interrupts and spurious wakeups are
possible, and this method should always be used in a loop:
synchronized (obj) {
while (<condition does not hold>)
obj.wait();
... // Perform action appropriate to condition
}
This method should only be called by a thread that is the owner
of this object's monitor. See the
notify
method for a
description of the ways in which a thread can become the owner of
a monitor.
Causes current thread to wait until either another thread invokes the
method or the
method for this object, or a
specified amount of time has elapsed.
The current thread must own this object's monitor.
This method causes the current thread (call it T) to
place itself in the wait set for this object and then to relinquish
any and all synchronization claims on this object. Thread T
becomes disabled for thread scheduling purposes and lies dormant
until one of four things happens:
- Some other thread invokes the notify method for this
object and thread T happens to be arbitrarily chosen as
the thread to be awakened.
- Some other thread invokes the notifyAll method for this
object.
- Some other thread interrupts
thread T.
- The specified amount of real time has elapsed, more or less. If
timeout is zero, however, then real time is not taken into
consideration and the thread simply waits until notified.
The thread
T is then removed from the wait set for this
object and re-enabled for thread scheduling. It then competes in the
usual manner with other threads for the right to synchronize on the
object; once it has gained control of the object, all its
synchronization claims on the object are restored to the status quo
ante - that is, to the situation as of the time that the
wait
method was invoked. Thread
T then returns from the
invocation of the
wait method. Thus, on return from the
wait method, the synchronization state of the object and of
thread
T is exactly as it was when the
wait method
was invoked.
A thread can also wake up without being notified, interrupted, or
timing out, a so-called spurious wakeup. While this will rarely
occur in practice, applications must guard against it by testing for
the condition that should have caused the thread to be awakened, and
continuing to wait if the condition is not satisfied. In other words,
waits should always occur in loops, like this one:
synchronized (obj) {
while (<condition does not hold>)
obj.wait(timeout);
... // Perform action appropriate to condition
}
(For more information on this topic, see Section 3.2.3 in Doug Lea's
"Concurrent Programming in Java (Second Edition)" (Addison-Wesley,
2000), or Item 50 in Joshua Bloch's "Effective Java Programming
Language Guide" (Addison-Wesley, 2001).
If the current thread is
interrupted
by another thread
while it is waiting, then an InterruptedException is thrown.
This exception is not thrown until the lock status of this object has
been restored as described above.
Note that the wait method, as it places the current thread
into the wait set for this object, unlocks only this object; any
other objects on which the current thread may be synchronized remain
locked while the thread waits.
This method should only be called by a thread that is the owner
of this object's monitor. See the notify
method for a
description of the ways in which a thread can become the owner of
a monitor.
Causes current thread to wait until another thread invokes the
method or the
method for this object, or
some other thread interrupts the current thread, or a certain
amount of real time has elapsed.
This method is similar to the wait
method of one
argument, but it allows finer control over the amount of time to
wait for a notification before giving up. The amount of real time,
measured in nanoseconds, is given by:
1000000*timeout+nanos
In all other respects, this method does the same thing as the
method
of one argument. In particular,
wait(0, 0) means the same thing as wait(0).
The current thread must own this object's monitor. The thread
releases ownership of this monitor and waits until either of the
following two conditions has occurred:
- Another thread notifies threads waiting on this object's monitor
to wake up either through a call to the
notify
method
or the notifyAll
method.
- The timeout period, specified by
timeout
milliseconds plus nanos
nanoseconds arguments, has
elapsed.
The thread then waits until it can re-obtain ownership of the
monitor and resumes execution.
As in the one argument version, interrupts and spurious wakeups are
possible, and this method should always be used in a loop:
synchronized (obj) {
while (<condition does not hold>)
obj.wait(timeout, nanos);
... // Perform action appropriate to condition
}
This method should only be called by a thread that is the owner
of this object's monitor. See the
notify
method for a
description of the ways in which a thread can become the owner of
a monitor.