How to have a function constantly execute in a Matlab Guide GUI?

I am trying to create the following GUI:

Monitor a textbox. If the input of the textbox changes, change the background color of another textbox for half a second, and then revert it back.

The way I thought about doing this is having a function that is constantly executing, checking in a while loop if the input of the textbox has changed. If it has changed, change the color of the textbox and wait half a second. Then change it back.

The problem is that I am not sure how to have a function that is always executing. All of the button functions and other things in the matlab gui guide only execute when they are pushed or pressed.

Answer 1

[Randy Acheson]

You can have a callback called regularly during the duration of a program by using the 'timer' object. Create a timer in the OpeningFcn of your GUIDE application, and assign it the callback you wish to call repeatedly. Here is an example:

function TestGUI_OpeningFcn(hObject, eventdata, handles, varargin)
% This function has no output args, see OutputFcn.
% hObject    handle to figure
% eventdata  reserved - to be defined in a future version of MATLAB
% handles    structure with handles and user data (see GUIDATA)
% varargin   command line arguments to untitled (see VARARGIN)

% Choose default command line output for untitled
handles.output = hObject;

t = timer();
t.Period = 2;
t.ExecutionMode = 'fixedRate';
t.TimerFcn = @TimerFcn; % Here is where you assign the callback function
handles.timer = t; % Put the timer object inside handles so that you can stop it later

start

(t)

% Update handles structure
guidata(hObject, handles);

Then, when you want to stop the timer, you can do so in any callback in your application with this line:

stop(handles.timer)

For an alternative approach, see this MATLAB Answers post:

https://www.mathworks.com/matlabcentral/answers/95584-how-can-i-make-the-text-that-i-enter-into-an-edit-text-box-update-dynamically

[Konvictus177]

Does this slow down the app? Does calling the function repeatedly with the timer object slow down other processes running in the app?