How to add Undo and Redo actions to JPanel

[Digen Mahara]

I am trying to make a paint application and want to add undo and redo functions to it how can I do this

I have used UndoManager class with TextComponents but really confused with Containers like JPanel where you actually draw images


Please Help !!!

[Campbell Ritchie]

Undo Manager appears only to work with text components.
How are you drawing your images? Do you have some sort of ImageComponent class or similar? Can you put ImageComponents into some sort of List and go back and forth along the List?

[Paul Clapham]

Campbell Ritchie wrote:Undo Manager appears only to work with text components.

Not at all. UndoManager can work with any kind of edits at all. It's just that you have to write a subclass of UndoableEdit which essentially stores the "before" and "after" states in such a way that the undo() and redo() methods modify the view appropriately. For example an edit for a checkbox might look like this (not all required methods implemented):

public class CheckboxEdit {
  private boolean oldValue, newValue;
  public CheckboxEdit(boolean oldValue, boolean newValue) {
    this.oldValue = oldValue;
    this.newValue = newValue;
  }
  public void undo() {
    checkbox.setSelected(oldValue);
  }
  public void redo() {
    checkbox.setSelected(newValue);
  }
}

[Campbell Ritchie]

I was mistaken, obviously. Sorry.