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

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.

Answer 1

[MathWorks Support Team]

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.

Answer 2

[Xingwang Yong]

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