How to use Timer Callback in App Designer?

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Using the App Designer, I would like to use the Timer callback within a callback section of the code. However, I am unable to reference functions from within the app using the function handle. How do I go about this? 

Accepted Answer

MathWorks Support Team
MathWorks Support Team on 29 Jun 2017
In order to use the Timer Callback in App Designer, please follow the rules as follows-
1. Update the callback function signature to have four input arguments: 'app', 'obj', 'event', 'string_arg' as shown below:
function my_callback_fcn(app, obj, event, string_arg)
Note 'app' is the handle to the app object (this is necessary because the function is a method of the app), 'obj' is the handle to the timer, 'event' is the event data for the timer event, and 'string_arg' is the additional input argument specified by you.
2. Because the function my_callback_fcn is a method on the app object, you need to reference it using the 'app.' prefix.
To set the Timer object's properties like "t.StartFcn" and "t.StopFcn", please specify the callback function using the 'app.' prefix as shown below:
t.StartFcn = {@app.my_callback_fcn, 'my start message'};
t.StopFcn = {@app.my_callback_fcn, 'my stop message'};

More Answers (2)

mansour torabi
mansour torabi on 1 Oct 2021
Edited: mansour torabi on 1 Oct 2021
In App Designer:
In Properties section, define a Variable to hold time object:
properties (Access = public)
MyTimer = 0;
Inside startupFcn(app) (callback function when UI starts), config the timer object:
function startupFcn(app)
app.MyTimer = timer('Period',0.5,'ExecutionMode','fixedSpacing',...
'TasksToExecute', Inf);
app.MyTimer.TimerFcn = @app.TimerCallback; % Your Timer Callback
Inside methods section, Define TimerCallback function, like bellows:
methods (Access = public)
function TimerCallback(app, obj, event)
UpdateSomeUIcomponent(app, someValue)
Start the timer, for example, after some button clicked:
function YourButtonPushed(app, event)
You should, call stop(app.MyTimer); to stop the timer object, when your are done!

mk_lab on 29 Jun 2017
Hey! I am trying exactly the same.
What i already have:
app.checkStatusTimer = timer('StartDelay', 4, 'Period', 500e-3, 'TasksToExecute', Inf, 'ExecutionMode', 'fixedRate');
app.checkStatusTimer.TimerFcn = @(x,y)disp('Hello World!');
This works, every 500 ms 'Hello World!' is displayed. But I need to call a function instead, as described above.
Can you maybe give a code example? Or explain in a bit more detail what you mean with "Update the callback function signature"
Thanks in advance!!
Kevin J. Delaney
Kevin J. Delaney on 27 Mar 2018
Many thanks for posting this! Just what I needed. Kevin

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