How do I write a loop in MATLAB that continues until the user presses any key?

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I want to run a specific routine in a loop. However I want the user to be able to exit the loop and end the routine by pressing any key on the keyboard.

Accepted Answer

MathWorks Support Team
MathWorks Support Team on 5 Feb 2010
MATLAB does not have a function that scans for keyboard activity without interrupting the event stream.
However, if your program involves a figure window, you can utilize the ‘KeyPressFcn’ property. The 'KeyPressFcn' is called when a key is pressed with an active figure window. You can set this function to change the state of a flag that ends a loop. Copy the following functions to a MATLAB file, and execute the MATLAB file.
function myLoopingFcn()
global KEY_IS_PRESSED
KEY_IS_PRESSED = 0;
gcf
set(gcf, 'KeyPressFcn', @myKeyPressFcn)
while ~KEY_IS_PRESSED
drawnow
disp('looping...')
end
disp('loop ended')
function myKeyPressFcn(hObject, event)
global KEY_IS_PRESSED
KEY_IS_PRESSED = 1;
disp('key is pressed')
The code will display "looping" in the MATLAB Command Window until a key is pressed when the figure window is active.

More Answers (1)

Xingwang Yong
Xingwang Yong on 19 Aug 2021
A version uses nested function instead of global variable
function myLoopingFcn2()
KEY_IS_PRESSED = 0;
gcf
set(gcf, 'KeyPressFcn', @myKeyPressFcn)
while ~KEY_IS_PRESSED
drawnow
disp('looping...')
end
disp('loop ended')
function myKeyPressFcn(hObject, event)
KEY_IS_PRESSED = 1;
disp('key is pressed')
end
end

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