QuickTime for Java: A Developer's Notebook

Undoing an Edit

Critical to any kind of editing is the ability to back out of a change that had unintended or undesirable effects. Fortunately, controller-based cuts and pastes can be undone with some fairly simple calls.

How do I do that?

UndoableQTEditor builds on the original BasicQTEditor by adding an “undo” menu item. The doUndo( ) method it calls has an utterly trivial implementation:

public void doUndo( ) throws QTException {
  controller.undo( );
}

Note

Compile and run this example with ant run-ch03-undoableqteditor.

What just happened?

With a simple call to MovieController.undo() , the program gained the ability to undo a cut or paste, or any other destructive change made through the controller.

What about...

...multiple undoes? Or redoes? Ah, there’s the rub. Hit undo again and the cut or paste is redone, in effect undoing the undo.

Sadly, this is your dad’s “undo”...the undo from back in 1990, when a single level of undo was a pretty cool thing. Today, when users expect to perform multiple destructive actions with impunity, it’s not too impressive.