MATLAB: How to get the timer object from within the timer’s callbacks, such as ‘TimerFcn’ and ‘StopFcn’

callbackfindfindtimergcbtMATLABtimertimerfcntimerfind

It would be convenient if I could locate the timer that is executing its callbacks from within the callback itself. For example, if I store handle graphics handles to the timer's 'UserData' property, I would like to be able to access them from within the timer's callbacks.

Best Answer

By default, the timer function callbacks pass the timer object as the first argument, and the event data associated with the callback as the second argument. Therefore, you always have access to the timer object from within its callback.

For more information and to see an example of how to define a timer callback, refer to the "Creating Callback Functions" section of the following URL:

 <http://www.mathworks.com/access/helpdesk/help/techdoc/index.html?/access/helpdesk/help/techdoc/matlab_prog/f9-39541.html>

Related Solutions

MATLAB: Run pushbutton automatically as soon as the GUI is visible without pressing the pushbutton

In the OpenFcn callback, create a timer object configured for a single execution, and have the callback for the timer object be a call to the name of the callback for the pushbutton, passing in the handle of the pushbutton, then [], and then the handles variable. But do it like this:

handles.push_timer = timer(... various arguments ...);
guidata(hObject, handles);   %store a copy of handles complete with the push_timer
handles.push_timer.TimerFcn = @(hObject, event) YourGUI_pushbutton1_Callback(handles.pushbutton1, [], handles);
start(handles.push_timer)

That is, do not set the TimerFcn callback to refer to handles until after you have already stored the timer object in handles. The timer() function permits you to configure TimerFcn as an option at the time you create the timer, but do not do that. If you do that, then the value of handles that makes it into the callback will not include the timer object and you would risk the timer being deleted before it gets used.

MATLAB: Varying timer’s period inside the TimerFcn

This page mentions an approach to vary the period of timer: https://stackoverflow.com/questions/15576682/matlab-change-repeating-timer-period

Here I show the method mentioned in the second answer. This example sets a random time period between 1 to 5 seconds after each callback of timer.

t = timer('StartDelay', 1, 'TimerFcn', @timerFcn, ...
    'StopFcn', @timerStopFcn, 'ExecutionMode', 'singleShot');
start(t);
function timerFcn(obj, ~)
    disp(obj.StartDelay)
end
function timerStopFcn(obj, ~)
    period = randi([1 5]);
    obj.StartDelay = period;
    start(obj);
end

Best Answer

Related Solutions

MATLAB: Run pushbutton automatically as soon as the GUI is visible without pressing the pushbutton

MATLAB: Varying timer’s period inside the TimerFcn

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