Stop an infinite loop with a key

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Miguel Albuquerque
Miguel Albuquerque on 22 Jun 2022
Commented: Jan on 23 Jun 2022
Hey guys, I have this infinite loop and I want to exit the while loop and continue the code when I press the cancel button in the waitbar, but this button isnt working, what can I do?
% Start the module
dev.start();
fprintf('Start of LimeSDR\n');
tic;
start_time=datetime('now','Format','dd-MMM-uuuu HH:mm:ss.SSS');
hWaitbar = waitbar(0,'Receiving Samples', 'Name', 'Progress', ...
'CreateCancelBtn','setappdata(gcbf,''canceling'',1)');
setappdata(hWaitbar,'canceling',0);
while true
% Receive samples on RX1 channel
indRx1 = 1; % index of the last received sample
[samples1, ~, samplesLength1] = dev.receive(Fs*Ts,1);
bufferRx1(indRx1:indRx1+samplesLength1-1) = samples1;
TT=array2timetable(samples1,'SampleRate',Fs,'StartTime',start_time);
writetimetable(TT,'Timetable_Rx1.txt','Delimiter','bar');
type Timetable_Rx1.txt
pause(1);
if getappdata(hWaitbar,'canceling')
% Stop the if cancel button was pressed
disp('Stopped by user');
break;
end
delete(hWaitbar);
end
% Cleanup and shutdown by stopping the RX stream and having MATLAB delete the handle object.
dev.stop();
tempo_rececao=toc;
stop_time=datetime('now','Format','dd-MMM-uuuu HH:mm:ss.SSS');
clear dev;
fprintf('Stop of LimeSDR\n');

Accepted Answer

Jan
Jan on 22 Jun 2022
Edited: Jan on 22 Jun 2022
You delete the waitbar in the first iteration:
delete(hWaitbar);
Remove this line. or move it behind the loop.
I cannot imagine what you call "does not work", because if you delete the complete waitbar, there is no button to press at all. Maybe you have some orphaned waitbars from former trials?
  2 Comments
Jan
Jan on 23 Jun 2022
Explaining, what does not happen, is less useful thanto explain what is happening.
if getappdata(hWaitbar,'canceling')
Does this stop with an error, because there is no field "canceling" before you press the button?
Defining callbacks as CHAR vectors is not recommended. Such strings are evaluated in the base workspace. If you have redefined e.g. "gcbf" as a variable, the callback will fail. Prefer function handles:
hWaitbar = waitbar(0,'Receiving Samples', 'Name', 'Progress', ...
'CreateCancelBtn', @(h, e) setappdata(ancestor(h, 'figure'), canceling', 1));

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