GUIDE openingFnc called more than once

Hi, Is there somewhere I can put GUIDE initialization code that is guarantied to be called exactly once? I've found that openingFnc is called every time the GUI gets focus, and I'm not happy with the "set a flag to indicate you've done this before" hack.

[Guillaume]

I'm not happy with the "set a flag to indicate you've done this before"

Why not? That seems the easiest and simplest way to do what you want you want and is guaranteed to work.

I certainly wouldn't call it a hack.

[Yoni Sher]

Mostly because the flag doesn't exist on the first call, so it's "if ~(exist('flag') == 1)" which is not elegant.

Answer 1

[Jan]

Using a flag is perfect, but if ~(exist('flag') == 1) would be a very poor implementation. Remember that this would search in the complete Matlab path for the files 'flag.m', 'flag.mexw64', variables, Java classes, folders etc. also. This is slow and might not reflect what you need.

But adding a flag to the figure's ApplicationData is fine and secure:

flagIsSet = isappdata(FigureHandle, 'MyFlag');
setappdata(FigureHandle, 'MyFlag', true);

if flagIsSet
   % run your code, which should run once only
end

[Yoni Sher]

Thanks, this is helpful. I was indeed trying to avoid 'exist' because I knew it was inefficient, but I didn't remember why.

Answer 2

[Image Analyst]

The OpeningFcn is not called more than once for me. I've never noticed that and I've written hundreds of GUIs. I have a line at the end of my OpeningFcn that does:

% Print informational message so you can look in the command window and see the order of program flow.
fprintf('Now leaving myGuiName_OpeningFcn.\n');

I ran it. Cleared the command window, then went back to the GUI to put it in focus, and the line did not show up in the command window. So I can't reproduced. I could debug it if you attached the .m file and .fig file.

[Yoni Sher]

The problem I'm actually having is that I need to initialize hardware, and it's being initialized multiple times. I don't think the code will do you much good because I can't send you the hardware...

[Image Analyst]

How do you know it's being called multiple times? Did you put a fprintf() in the OpeningFcn like I did? Or did you put a breakpoint there?

[Yoni Sher]

I used a breakpoint, but even before that I knew it was being called multiple times because if the hardware is already initialized and someone tries to start it up again, all * breaks loose.

[Isaac Wolf]

I had been having the same issue, and I found out it was due to an "ishandle()" call I had in one of my other functions to make sure the GUI was still open.

Answer 3

[Walter Roberson]

The CreateFcn callback for the GUI will only be called once when the figure is loaded from the .fig file. Be warned that this will occur before the handles structure is created. The order of CreateFcn for the various components is not explicitly defined in the documentation.