Timer not working in my programmatic app (not app designer)

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Brendan Hall
Brendan Hall el 29 de Sept. de 2023
Comentada: Voss el 29 de Sept. de 2023
I have a programmatic app where I'm trying to periodically and automatically update a plot. Whenever I use the start(timer_object) it produces a message "Dot indexing is not supported for variables of this type". Here's the app:

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Voss el 29 de Sept. de 2023
Editada: Voss el 29 de Sept. de 2023
First, line 25:
%update_timer = data.update_timer;
needs to be uncommented for that error to happen (otherwise you get a different error because "update_timer" is undefined).
Errors in timer callbacks can be tricky to debug because the error message doesn't tell you what line it happened on. To debug it, you can put a breakpoint on the first line of the TimerFcn (axTimerFcn) and step through until you get the error. When you do that, you'll find that this line (line 31)
fig = ancestor(src,"figure","toplevel");
gives fig as an empty array [], which causes the error on the next line when you try to access fig.UserData. fig is empty because timers don't exist inside a figure the way uicontrols do, so ancestor is not going to work for them. You could use timerfind or timerfindall to find your timer object, but I recommend restructuring your code so that the callbacks (the uibutton ButtonPushedFcn StartTimer and the TimerFcn axTimerFcn) are nested inside the main function timer_app_1. Then they'll easily have access to whatever they need and it will no longer be necessary to have to store anything in the figure's UserData. Something like this:
function timer_app_1
fig = uifigure('Position',[100 50 2400 3.5*430],'AutoResizeChildren','off');
grid = uigridlayout(fig, [3 3]);
ax = uiaxes(grid);
ax.Layout.Column = 2;
ax.Layout.Row = 2;
uibutton(grid,"Text","Start Timer","ButtonPushedFcn",@StartTimer);
update_timer = timer('ExecutionMode', 'fixedRate', ... % Run timer repeatedly
'Period', 1, ... % Period is 1 second
'BusyMode', 'queue',... % Queue timer callbacks when busy
'TimerFcn', @axTimerFcn);
function StartTimer(~,~)
function axTimerFcn(~,~)
if i==10
  3 comentarios
Voss el 29 de Sept. de 2023
You're welcome!

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Más respuestas (1)

Walter Roberson
Walter Roberson el 29 de Sept. de 2023
The first parameter passed to a timer is the timer object, and the second parameter is the event data.
You are trying to
fig = ancestor(src,"figure","toplevel");
which is assuming that the first parameter is a graphics object rather than a timer object.
The easiest workaround is to use
update_timer = timer('ExecutionMode', 'fixedRate', ... % Run timer repeatedly
'Period', 1, ... % Period is 1 second
'BusyMode', 'queue',... % Queue timer callbacks when busy
'TimerFcn', @(src,event)axTimerFcn(fig,event));
so that fig gets passed as the first parameter to the callback function.


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