How to Create RT clock in my own GUI?

Hello,

I have the following code (it's upon GUI creation):

set(handles.time_caption,'String',datestr(now,13))
tmr = timer('Name','Reminder',                   ...
            'Period',1,                          ...  % Update the time every 1 seconds.
            'StartDelay',0,                      ...  % In seconds.
            'TasksToExecute',inf,                ...  % number of times to update
            'ExecutionMode','fixedSpacing',      ...
            'TimerFcn',{@updater_mg}); 
start(tmr);                                           % Start the timer object.

function [] = updater_mg(varargin)
    set(handles.time_caption , 'string' , datestr(now,13))
end

I receive the following error:

Error while evaluating TimerFcn for timer 'Reminder' 
Undefined variable "handles" or class "handles.time_caption".

I understand that when I'm "inside" the updater_mg function it doesn't recognize my handles struct from a layer above.

How can I overcome this?

Answer 1

[Jan]

If handles is unknown in the callback, provide it as input:

set(handles.time_caption,'String',datestr(now,13))
tmr = timer('Name','Reminder',                   ...
          'Period',1,                          ...  % Update the time every 1 seconds.
          'StartDelay',0,                      ...  % In seconds.
          'TasksToExecute',inf,                ...  % number of times to update
          'ExecutionMode','fixedSpacing',      ...
          'TimerFcn',{@updater_mg, handles});     % <== HERE

function updater_mg(TimerH, EventData, handles)   % <== AND HERE
  set(handles.time_caption , 'string' , datestr(now,13));
end

Add a security check:

function updater_mg(TimerH, EventData, handles)   % <== AND HERE
  if ishandle(handles.time_caption)
    set(handles.time_caption , 'string' , datestr(now,13));
  else
    disp('Timer for clock stopped: GUI was closed');
    stop(TimerH);
  end
end

[Mark Golberg]

great, thanks!!!

[Mark Golberg]

Just for my understanding, when defining time properties you wrote:

'TimerFcn',{@updater_mg, handles}

only one input variable - handles.

But, in the definition of the updater_mg function you wrote:

function updater_mg(TimerH, EventData, handles)

That's 3 inputs variables. Why is that? I mean, TimerH & EventData are not even being used.

And of course, if I try without them, I receive an error:

"not enough inputs"

[Jan]

Search in the documentation of Matlab for the term "callback":

docsearch callback

There you find the description, that all callbacks get two default inputs: The handle of the affected object and a description of the event. Therefore definining the callback with 1 output means, that it is called with 3 inputs. For 'TimerFcn', @updater_mg the callback would get 2 inputs.

[Mark Golberg]

Great, Thanks again.