Class CommandStack


  • public class CommandStack
    extends java.lang.Object
    An implementation of a command stack. A stack manages the executing, undoing, and redoing of Commands. Executed commands are pushed onto a a stack for undoing later. Commands which are undone are pushed onto a redo stack. Whenever a new command is executed, the redo stack is flushed.

    A CommandStack contains a dirty property. This property can be used to determine when persisting changes is required. The stack is dirty whenever the last executed or redone command is different than the command that was at the top of the undo stack when markSaveLocation() was last called. Initially, the undo stack is empty, and not dirty.

    • Field Detail

      • POST_EXECUTE

        public static final int POST_EXECUTE
        Constant indicating notification after a command has been executed.
        See Also:
        Constant Field Values
      • POST_REDO

        public static final int POST_REDO
        Constant indicating notification after a command has been redone.
        See Also:
        Constant Field Values
      • POST_UNDO

        public static final int POST_UNDO
        Constant indicating notification after a command has been undone.
        See Also:
        Constant Field Values
      • POST_FLUSH

        public static final int POST_FLUSH
        Constant indicating notification after flushing the stack.
        Since:
        3.11
        See Also:
        Constant Field Values
      • POST_MARK_SAVE

        public static final int POST_MARK_SAVE
        Constant indicating notification after marking the save location of the stack.
        Since:
        3.11
        See Also:
        Constant Field Values
      • POST_MASK

        public static final int POST_MASK
        A bit-mask indicating notification after the command stack has changed. This includes after a command has been undone, redone, or executed, as well as after it has been flushed or the save location has been marked.

        Usage

         if ((commandStackEvent.getDetail() & CommandStack.POST_MASK) != 0) {
                // Do something, like:
                stopBatchingChanges();
         }
         
      • PRE_EXECUTE

        public static final int PRE_EXECUTE
        Constant indicating notification prior to executing a command.
        See Also:
        Constant Field Values
      • PRE_REDO

        public static final int PRE_REDO
        Constant indicating notification prior to redoing a command.
        See Also:
        Constant Field Values
      • PRE_UNDO

        public static final int PRE_UNDO
        Constant indicating notification prior to undoing a command.
        See Also:
        Constant Field Values
      • PRE_FLUSH

        public static final int PRE_FLUSH
        Constant indicating notification prior to flushing the stack.
        Since:
        3.11
        See Also:
        Constant Field Values
      • PRE_MARK_SAVE

        public static final int PRE_MARK_SAVE
        Constant indicating notification prior to marking the save location of the stack.
        Since:
        3.11
        See Also:
        Constant Field Values
      • PRE_MASK

        public static final int PRE_MASK
        A bit-mask indicating notification before the command stack is changed. This includes before a command has been undone, redone, or executed, and before the stack is being flushed or the save location is marked.

        Usage

         if ((commandStackEvent.getDetail() & CommandStack.PRE_MASK) != 0) {
                // Do something, like:
                startBatchingChanges();
         }
         
        Since:
        3.7 Had package visibility before.
    • Constructor Detail

      • CommandStack

        public CommandStack()
        Constructs a new command stack. By default, there is no undo limit, and isDirty() will return false.
    • Method Detail

      • addCommandStackEventListener

        public void addCommandStackEventListener​(CommandStackEventListener listener)
        Appends the listener to the list of command stack listeners. Multiple adds result in multiple notifications.
        Parameters:
        listener - the event listener
        Since:
        3.1
      • canRedo

        public boolean canRedo()
        Returns:
        true if it is appropriate to call redo().
      • canUndo

        public boolean canUndo()
        Returns:
        true if undo() can be called
      • dispose

        public void dispose()
        This will dispose() all the commands in both the undo and redo stack. Both stacks will be empty afterwards.
      • execute

        public void execute​(Command command)
        Executes the specified Command if possible. Prior to executing the command, a CommandStackEvent for PRE_EXECUTE will be fired to event listeners. Similarly, after attempting to execute the command, an event for POST_EXECUTE will be fired. If the execution of the command completely normally, stack listeners will receive stackChanged notification.

        If the command is null or cannot be executed, nothing happens.

        Parameters:
        command - the Command to execute
        See Also:
        CommandStackEventListener
      • flush

        public void flush()
        Flushes the entire stack and resets the save location to zero. This method might be called when performing "revert to saved".
      • getCommands

        public java.lang.Object[] getCommands()
        Returns:
        an array containing all commands in the order they were executed
      • getRedoCommand

        public Command getRedoCommand()
        Peeks at the top of the redo stack. This is useful for describing to the User what will be redone. The returned Command has a label describing it.
        Returns:
        the top of the redo stack, which may be null
      • getUndoCommand

        public Command getUndoCommand()
        Peeks at the top of the undo stack. This is useful for describing to the User what will be undone. The returned Command has a label describing it.
        Returns:
        the top of the undo stack, which may be null
      • getUndoLimit

        public int getUndoLimit()
        Returns the undo limit. The undo limit is the maximum number of atomic operations that the User can undo. -1 is used to indicate no limit.
        Returns:
        the undo limit
      • isDirty

        public boolean isDirty()
        Returns true if the stack is dirty. The stack is dirty whenever the last executed or redone command is different than the command that was at the top of the undo stack when markSaveLocation() was last called.
        Returns:
        true if the stack is dirty
      • markSaveLocation

        public void markSaveLocation()
        Marks the last executed or redone Command as the point at which the changes were saved. Calculation of isDirty() will be based on this checkpoint.
      • notifyListeners

        protected void notifyListeners​(Command command,
                                       int state)
        Notifies command stack event listeners that the command stack has changed to the specified state.
        Parameters:
        command - the command
        state - the current stack state
        Since:
        3.2
      • redo

        public void redo()
        Calls redo on the Command at the top of the redo stack, and pushes that Command onto the undo stack. This method should only be called when canUndo() returns true.
      • removeCommandStackEventListener

        public void removeCommandStackEventListener​(CommandStackEventListener listener)
        Removes the first occurrence of the specified listener.
        Parameters:
        listener - the listener
      • removeCommandStackListener

        public void removeCommandStackListener​(CommandStackListener listener)
        Deprecated.
        Removes the first occurrence of the specified listener.
        Parameters:
        listener - the listener
      • setUndoLimit

        public void setUndoLimit​(int undoLimit)
        Sets the undo limit. The undo limit is the maximum number of atomic operations that the User can undo. -1 is used to indicate no limit.
        Parameters:
        undoLimit - the undo limit
      • undo

        public void undo()
        Undoes the most recently executed (or redone) Command. The Command is popped from the undo stack to and pushed onto the redo stack. This method should only be called when canUndo() returns true.