timer error in guide

hello everybody.

I'm trying to implement a timer object om guide. the idiea is to invoke a function every couple of second.

the function monitor check ip data and renders the relevant cell in the table repetedly

I saw an example but somehow it doesnt work well I get the following error:

Error while evaluating TimerFcn for timer 'timer-10'

H must be the handle to a figure or figure descendent.

my code: function app_OpeningFcn(hObject, eventdata, handles, varargin) .

.

handles.timer = timer(... 'ExecutionMode', 'fixedSpacing', ... % Run timer repeatedly 'Period', 1, ... % Initial period is 1 sec. 'TimerFcn', {@uitable2_CellEditCallback,handles});

 *the function:*

function uitable2_CellEditCallback(hObject, eventdata, handles)

guidata(hObject)

str='wmic path Win32_PerfRawData_Tcpip_NetworkInterface Get BytesReceivedPersec';

[~,cmdout] = system(str);

cmdout=cmdout(24:end);len=(length(cmdout)-2)/23;

recv=cell(len,1);

for ii=0:len-1

    recv(ii+1)={cmdout(ii*23+1:ii*23+23)};

end

rate=cellfun(@(x) str2num(x),recv,'UniformOutput' , false);rate=[rate{:}]';

handles.current=rate(~rate(:)==0);lngth=length(handles.current);

handles.uitable2.Data(1:lngth,4)=num2cell(rate(~rate(:)==0));

guidata(hObject,handles)

I get the error message when I call this function:

function pushbutton6_Callback(hObject, eventdata, handles)

if strcmp(get(handles.timer, 'Running'), 'off')

    start(handles.timer);

end

I would appriciate any help,

Elad

Answer 1

[Steven Lord]

Quoting the relevant lines with formatting applied, your call to timer is:

handles.timer = timer(... 'ExecutionMode', 'fixedSpacing', ... % Run timer repeatedly
  'Period', 1, ... % Initial period is 1 sec.
  'TimerFcn', {@uitable2_CellEditCallback,handles});

By the way you specify your TimerFcn, uitable2_CellEditCallback will be called with the third argument a copy of the handles structure AS IT EXISTS AT THIS MOMENT. Any changes you make to the handles structure later on WILL NOT BE REFLECTED in the copy passed into your callback. [The emphasis on those two phrases is because I've seen a lot of people confused by this in the past, and it can be difficult to realize the cause of the problem.]

If this is your intention, you can use this approach; otherwise I would pass the handle to something fixed, where the handle will not change, into the TimerFcn and retrieve the handles structure using that handle. I would probably use the handle of the main figure in your GUI, as it's unlikely you're going to close that main figure without first stopping the timer.

Now on to the main issue. Your TimerFcn is, in part:

function uitable2_CellEditCallback(hObject, eventdata, handles)
guidata(hObject)

The first input to a TimerFcn is the handle to the timer itself.

 "When you create a callback function, the first two arguments must be a handle
 to the timer object and an event structure."

The guidata function expects you to pass a graphics object handle as its input, not a timer object. If you use my suggestion from above and pass the handle to your main GUI figure in as the third input, that GUI figure handle would make a fine input to guidata.

Answer 2

[Elad]

Hi Steven,

Thanks for the quick response.

you wrote: "When you create a callback function, the first two arguments must be a handle to the timer object and an event structure."

did you mean that my callback should look like

uitable2_CellEditCallback(timer_handel,eventdata)? is this syntax leagal?

now, I've specified my callback function uitable2_CellEditCallback as the timerFunc. when I hit start(handles.timer) what is being passed to uitable2_cellEditCallback? and what should I pass in order to make it work?

I need to change continually data stored in handles as my gui runs. and present it in a table.

can you write explicitly what should I pass? or how should I pass those arguments?

Thank you very much!

Elad

[Steven Lord]

When the timer object calls your TimerFcn, it will automatically pass the timer object and the event data into your TimerFcn. You must define your TimerFcn to accept at least two inputs plus any additional inputs that you want to pass in. See the examples on the documentation page to which I linked.