Hi, I have a few controls on my sketch. I didn't change any code in gui.pde (except places where editing is allowed). However, now when I try to open GUI Builder, it gives me this error:

I can only think of two possibilities:

1. The GUI was created with an earlier version of GUI Builder and you are attempting to edit it with a later version. GUI Builder uses serialisation to save a GUI design to a file, in most cases the design cannot be loaded by a leter version depending on the changes made between versions.
2. That you accidentally corrupted the comment-markes placed at the start and end of the event handlers in the gui tab. If this is a possibility then try the followiing - copy all the code in the gui tab and paste into some othet text editor - delete all the event handler methods - click (or open) the GUI Builder tool - then go back to the PDE. If all went well copy and paste the event handler code from the copy into the event handler methods (do not copy the whole method)

**update: if I add an options group, and then add Option controls, I don't get any error. 

BUT, if I add an options group, and click on the options group (just to rename or simply click on it) and then add the option controls, it gives error. I am surprised, I didn't even change anything. Only clicking on the OptionsGroup creates this problem?

You are surpised? I am amazed because no one has reported a similar problem and I was unable to reproduce the error? In fact what was the error message?

Please post your video to youtube and then paste a link here. The site required me to instal a codec and I only install files from sites I know or have researched (and I don't have time to research this one)

.mov files are Apple's QuickTime video CoDec.

That site doesn't require anything. You can just download it and play it offline.
I was able to play it even in my Lubuntu Linux OS!

If you don't have QuickTime CoDec installed or prefer not to install it system-wide,
you can use a video player like VLC which comes w/ its own CoDecs!

I was in a hurry when I visited the site and the download buttons wanted me to instal some codec. I am not familiar with this site and I am ultra-cautious when installing software from the Internet. I did not notice the smaller download button which downloaded just the movie until now. So I have downloaded and viewed the movie.

When you move from the GUI Builder tool window to the Processing window the current design is saved using serialisation and the content of the gui.pde file is re-generated. The error seems to be in the serialisation.

Using the current version of G4P (3.3) and GUI Builder (2.3) with Processing 2.0.1 I am unable to reproduce the error so there is not a lot I can do, but thanks for taking the time to make the movie.

I notice that you are using V2.2.2 of GUI Builder so perhaps it is time to get the latest versions of G4P and GUI Builder.

I read in a post that it is not a good idea to update from previous versions to the new GUI Builder

When you create a GUI with this tool it saves the design using Java serialisation but this has some limitations. It means that a design created with an earlier version ofGUI Builder cannot be read by a later version (giving you the sort of error you got above.

cannot that is not strictly true, in some cases GUI Builder can read GUIs created with earlier versions. It depends on what changes I have made to the code and what types control have been used in the design.

I could have used XML to save the design so there would always be backward compatability but there were two reasons why I used serialisation.

1. I anticipated the creation of the GUI would be a small part of a sketch and that once created it would not likely be edited. (At least for small sketches)
2. It would have involved a lot more work (for me) to have used XML.

I love this tool! And I will update it as soon as I am done with my current project.

The changes made in the latest version of GUI Builder would almost certainly mean that you are best to finish your GUI with the version you are using. BTW I love this tool as well

For the record, in case someday you will want to investigate the XML solution, quarks:
- Indeed, serialization in Java is simple and powerful... and brittle (that's why there is a serialVersionID constant): you can only deserialize an object with exactly the same class structure than used for serialization. Add a field (non static final, non transient, etc.) and you break the reading of previous values. So either you are stuck with your format, or must break previous saves.
- This serialization is done in binary, so it is near impossible to change the output. In projects where it is critical, you might need to keep the old class to read the values, convert to the new class and save in the new format.
- Using a simple textual format is only slightly better (somehow at the expense of file size, but it is rarely a problem): it can still be unable to load an old class. At least, for simple cases, you can imagine a script (XSLT, Perl, whatever) to do the transformation as a tool.
- A library like Xstream can help, because it is very flexible: you can declare fields as optional, recover from missing fields, have custom behavior in case of problems, etc.