Package org.eclipse.core.commands

Class AbstractHandler

java.lang.Object

org.eclipse.core.commands.common.EventManager

org.eclipse.core.commands.AbstractHandler

All Implemented Interfaces:

IHandler, IHandler2

Direct Known Subclasses:

AbstractHandler, AbstractHandlerWithState, ActionHandler, CollapseAllHandler, DebugCommandHandler, ExpandAllHandler, FileBufferOperationHandler, MarkerViewHandler, MergeActionHandler, NewPropertySheetHandler, ShowPerspectiveHandler, ShowViewHandler, TextZoomInHandler, TextZoomOutHandler

public abstract class AbstractHandler
extends EventManager
implements IHandler2

This class is a partial implementation of IHandler. This abstract implementation provides support for handler listeners. You should subclass from this method unless you want to implement your own listener support. Subclasses should call fireHandlerChanged(HandlerEvent)when the handler changes. Subclasses can also override isEnabled() and isHandled().

Since:

3.1

Constructor Summary

Constructors

Constructor	Description
AbstractHandler()

Method Summary

Modifier and Type	Method	Description
void	addHandlerListener(IHandlerListener handlerListener)	Registers an instance of IHandlerListener to listen for changes to properties of this instance.
void	dispose()	The default implementation does nothing.
protected void	fireHandlerChanged(HandlerEvent handlerEvent)	Fires an event to all registered listeners describing changes to this instance.
protected boolean	hasListeners()	Returns true iff there is one or more IHandlerListeners attached to this AbstractHandler.
boolean	isEnabled()	Whether this handler is capable of executing at this time.
boolean	isHandled()	Whether this handler is capable of handling delegated responsibilities at this time.
void	removeHandlerListener(IHandlerListener handlerListener)	Unregisters an instance of IHandlerListener listening for changes to properties of this instance.
protected void	setBaseEnabled(boolean state)	Allow the default isEnabled() to answer our enabled state.
void	setEnabled(Object evaluationContext)	Called by the framework to allow the handler to update its enabled state by extracting the same information available at execution time.

Methods inherited from class org.eclipse.core.commands.common.EventManager

addListenerObject, clearListeners, getListeners, isListenerAttached, removeListenerObject

Methods inherited from class java.lang.Object

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

Methods inherited from interface org.eclipse.core.commands.IHandler

execute

Constructor Detail

AbstractHandler

public AbstractHandler()

Method Detail

addHandlerListener

public void addHandlerListener(IHandlerListener handlerListener)

Description copied from interface: IHandler

Registers an instance of IHandlerListener to listen for changes to properties of this instance.

Specified by:

addHandlerListener in interface IHandler

Parameters:

handlerListener - the instance to register. Must not be null. If an attempt is made to register an instance which is already registered with this instance, no operation is performed.

dispose

public void dispose()

The default implementation does nothing. Subclasses who attach listeners to other objects are encouraged to detach them in this method.

Specified by:

dispose in interface IHandler

fireHandlerChanged

protected void fireHandlerChanged(HandlerEvent handlerEvent)

Fires an event to all registered listeners describing changes to this instance.

Subclasses may extend the definition of this method (i.e., if a different type of listener can be attached to a subclass). This is used primarily for support of AbstractHandler in org.eclipse.ui.workbench, and clients should be wary of overriding this behaviour. If this method is overridden, then the first line of the method should be "super.fireHandlerChanged(handlerEvent);".

Parameters:

handlerEvent - the event describing changes to this instance. Must not be null.

isEnabled

public boolean isEnabled()

Whether this handler is capable of executing at this time. Subclasses may override this method. If clients override this method they should also consider overriding setEnabled(Object) so they can be notified about framework execution contexts.

Specified by:

isEnabled in interface IHandler

Returns:

true

See Also:

setEnabled(Object), setBaseEnabled(boolean)

setBaseEnabled

protected void setBaseEnabled(boolean state)

Allow the default isEnabled() to answer our enabled state. It will fire a HandlerEvent if necessary. If clients use this method they should also consider overriding setEnabled(Object) so they can be notified about framework execution contexts.

Parameters:

state - the enabled state

Since:

3.4

setEnabled

public void setEnabled(Object evaluationContext)

Called by the framework to allow the handler to update its enabled state by extracting the same information available at execution time. Clients may override if they need to extract information from the application context.

Specified by:

setEnabled in interface IHandler2

Parameters:

evaluationContext - the application context. May be null

Since:

3.4

See Also:

setBaseEnabled(boolean)

isHandled

public boolean isHandled()

Whether this handler is capable of handling delegated responsibilities at this time. Subclasses may override this method.

Specified by:

isHandled in interface IHandler

Returns:

true

hasListeners

protected boolean hasListeners()

Returns true iff there is one or more IHandlerListeners attached to this AbstractHandler.

Subclasses may extend the definition of this method (i.e., if a different type of listener can be attached to a subclass). This is used primarily for support of AbstractHandler in org.eclipse.ui.workbench, and clients should be wary of overriding this behaviour. If this method is overridden, then the return value should include "super.hasListeners() ||".

Returns:

true iff there is one or more IHandlerListeners attached to this AbstractHandler

removeHandlerListener

public void removeHandlerListener(IHandlerListener handlerListener)

Description copied from interface: IHandler

Unregisters an instance of IHandlerListener listening for changes to properties of this instance.

Specified by:

removeHandlerListener in interface IHandler

Parameters:

handlerListener - the instance to unregister. Must not be null. If an attempt is made to unregister an instance which is not already registered with this instance, no operation is performed.