Referencing GUI object in function

Totally new to MatLab and OO programming, but I do know C quite well.

Was given a MatLab app code with GUI to put some finishing touches on. I've successfully worked with the GUI, referenced objects, updated stuff on the GUI and code successfully for a week now, so basically I know my way around. What's stumping me is: I have a function that was created by the vendor, but it's buried in a dll so I can't change the parameters to pass from the GUI into the function directly.

What I'm doing: I created a Static Text object in the GUI with the tag ' _ storing_'. It sits inside a uipanel1, and that inside my only figure named Figure. I want to change the static text's item's text string when something code-wise happens.

Below is the basic premise and error thrown. I've seen where lots of people have asked the same type question, I've tried at least a dozen recommended code solutions to reference the GUI object inside the vendor function without success.

I get what's happening, the object is outside the scope of the function, I just can't seem to figure out the MatLab calls to allow me to how to pass the object's handle inside the function to update the text. Can someone help please?

    % --- NOT MY FUNCTION 
  function FrameCallback(sender,args)
  try
      if (thisExecutesOk)
           % ...some stuff happens. The item is initially not visible so I try to turn it on. This is where it throws an error...
          set(handles.storing,'visible','on');  % It jumps to 'catch' so the next line never gets called
          set(handles.storing,'string',strcat('Storing... ',num2str(getFrameCounter-1)));  % This works fine outside of the function
      end
    catch E
      msg = E;
  end

Error thrown is:

%

[Geoff Hayes]

Scott - if you assign a tag to your GUI and set the HandleVisibility property to on, then you may be able to reference that GUI from the callback (see https://www.mathworks.com/matlabcentral/answers/146215-pass-data-between-gui-s for details). Your code could be something like

 function FrameCallback(sender,args)
  try
      if (thisExecutesOk)
          hGui = findobj('Tag','Gui1');
          if ~isempty(hGui)
              handles = guidata(hGui);
              % etc.
          end
      end
   catch E
      msg = E;
   end

[Geoff Hayes]

Scott - how have you created the GUI? Programmatically or with GUIDE or with AppDesigner?

If using GUIDE and since your GUI tag is set to 'mainPanel', then what happens if you try

 hGui = findobj('Tag','mainPanel');

What does this return? (When called from within your function.) Is hGui empty or a handle to your figure/GUI? If the latter, what does

 handles = guidata(hGui);

return? Another empty object or a structure with handles to all UI controls of your GUI?

[Scott Rodriguez]

Got it, thanks! I was trying to use the Tag name as the parameter for 'Tag', but I see now 'Tag' specifies the property, and the following quote is the tag of the object. Tell it what it is you're about to tell it, then tell it what it is.

Need some fundamental training, but was just told to get it going and move on. Thanks~!

[Geoff Hayes]

right, you pass in pairs of elements to findobj: the property string name and the property value.

[Image Analyst]

But we still have the problem of getting GUI parameters/settings into "a function that was created by the vendor, but it's buried in a dll so I can't change the parameters". How is this DLL going to find out about the values if it doesn't let you set them?

[Geoff Hayes]

Maybe the function FrameCallback(sender,args) is called by the DLL (somehow)?

Answer 1

[Image Analyst]

I don't understand. Is FrameCallback(sender,args) your function or not, or if it's not your function but do you have the source code for it? It seems like you have it because you proposed some changed code for the inside of that function.

Anyway, what does that code have to do with some DLL that you're calling? If you're using loadlibrary() to load some vendor's DLL so that you can call it, then what does that have to do with FrameCallback()?

Anyway, it should work as long as you have a control called storing and you have access to handles. Either pass handles in to FrameCallback()

function handles = FrameCallback(handles, sender, args)

or try to find it using the code Geoff gave you. If you don't want to pass handles back out, you can call guidata() to update it instead.

Then you can use modern OOP syntax like this:

handles.storing.Visible = 'on';
handles.storing.String = sprintf('Storing %d.', getFrameCounter-1);

Anyway, I don't think any of that will help you with setting parameters internal to the DLL that are not exposed and you're not able to set by passing values into the DLL for them, because, as you say "it's buried in a dll so I can't change the parameters to pass". If the DLL is not willing to let you send in new values, then you are probably out of luck.

[Scott Rodriguez]

IA, thanks for the reply. I do have the code definition but do not have access to the declaration, so I can't change the parameter set to pass the GUI's handles. I assumed it was buried in one of the many dll's provided by Fluke, I could be wrong. This is an example of how the function is being called as a parameter of another Fluke-proprietary function inside the MatLab app:

Fluke.Thermography.IRAccess.Streaming.StreamSource.Instance.UnregisterFrameCallback(@FrameCallback);