org.eclipse.gef.commands
Class AbstractCommand

java.lang.Object
  |
  +--org.eclipse.gef.commands.AbstractCommand

All Implemented Interfaces:

Command

Direct Known Subclasses:

CompoundCommand, UnexecutableCommand

public abstract class AbstractCommand

extends Object

implements Command

Fields inherited from interface org.eclipse.gef.commands.Command

copyright

Constructor Summary

AbstractCommand()

AbstractCommand(String label)

Method Summary

boolean	canExecute() This indicates whether the comamad is valid to execute.
boolean	canUndo() This returns whether the command can be undone.
Command	chain(Command command) This logically chains the given command to this command, by returning a command that represents the composition.
void	dispose() This is called to indicate that the command will never be used again.
void	execute() This will perform the command activity required for the effect.
Collection	getAffectedObjects() This returns the collection of things which this command wishes to present as the objects affected by the command.
String	getDebugLabel()
String	getDescription() This returns a string suitable to help describe the effect of this command.
String	getLabel() This returns a string suitable to represent the label that identifies this command.
Collection	getResult() This returns collection of things which this command wishes to present as it's result.
void	redo() This will again perform the command activity required to redo the effect after undoing the effect.
void	setDebugLabel(String label)
void	setDescription(String label)
void	setLabel(String label)
void	undo() This will perform the command activity required to undo the effects of a preceding execute (or redo).

Methods inherited from class java.lang.Object

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

Constructor Detail

AbstractCommand

public AbstractCommand()

AbstractCommand

public AbstractCommand(String label)

Method Detail

getAffectedObjects

public Collection getAffectedObjects()

Description copied from interface: Command

This returns the collection of things which this command wishes to present as the objects affected by the command. Typically should could be used as the selection that should be highlighted to best illustrate the effect of the command. The result of calling this before an execute, redo, or undo is undefined. The result may be different after an undo than it is after an execute or redo, but the result should be the same (equivalent) after either an execute or redo.

Specified by:

getAffectedObjects in interface Command

getDebugLabel

public String getDebugLabel()

getDescription

public String getDescription()

Description copied from interface: Command

This returns a string suitable to help describe the effect of this command.

Specified by:

getDescription in interface Command

getLabel

public String getLabel()

Description copied from interface: Command

This returns a string suitable to represent the label that identifies this command.

Specified by:

getLabel in interface Command

getResult

public final Collection getResult()

Description copied from interface: Command

This returns collection of things which this command wishes to present as it's result. The result of calling this before an execute or redo, or after an undo, is undefined.

Specified by:

getResult in interface Command

canExecute

public boolean canExecute()

Description copied from interface: Command

This indicates whether the comamad is valid to execute. The UnexecutableCommand.INSTANCE.canExecute() always returns false. This must be called before calling execute.

Specified by:

canExecute in interface Command

canUndo

public boolean canUndo()

Description copied from interface: Command

This returns whether the command can be undone. The result of calling this before execute is well defined, but the result of calling this before calling canExecute is undefined, i.e., a command that retuns false for canExecute may return true for canUndo, even though that is a contradiction.

Specified by:

canUndo in interface Command

chain

public Command chain(Command command)

Description copied from interface: Command

This logically chains the given command to this command, by returning a command that represents the composition. The resulting command may just be this, if this command is capabable of composition. Otherwise, it will be a new command created to compose the two.

Instead of the following pattern of usage

   Command result = x;
   if (condition) result = result.chain(y);
 

you should consider using a CompoundCommand and using CompoundCommand.unwrap() to optimize the result:

   CompoundCommand subcommands = new CompoundCommand();
   subcommands.append(x);
   if (condition) subcommands.append(y);
   Command result = subcommands.unwrap();
 

This gives you more control over how the compound command composes it's result and affected objects.

Specified by:

chain in interface Command

dispose

public void dispose()

Description copied from interface: Command

This is called to indicate that the command will never be used again. Calling any other method after this one has undefined results.

Specified by:

dispose in interface Command

execute

public void execute()

Description copied from interface: Command

This will perform the command activity required for the effect. The effect of calling execute when canExecute returns false, or when canExecute hasn't been called, is undefined.

Specified by:

execute in interface Command

redo

public void redo()

Description copied from interface: Command

This will again perform the command activity required to redo the effect after undoing the effect. The effect, if any, of calling redo before undo is called is undefined. Note that if you implement redo to call execute then any derived class will be restricted to by that decision also.

Specified by:

redo in interface Command

setDebugLabel

public void setDebugLabel(String label)

setDescription

public void setDescription(String label)

setLabel

public void setLabel(String label)

undo

public void undo()

Description copied from interface: Command

This will perform the command activity required to undo the effects of a preceding execute (or redo). The effect, if any, of calling undo before execute or redo have been called, or when canUndo returns false, is undefined.

Specified by:

undo in interface Command