How to close a figure used for keypress function?

Hi,

I'm using the KeyPressFnc to capture user-feedback in a small test. The use of KeyPressFnc requires to open a (dummy) figure. To complete the test (aka run the code clean from top to bottom) I have to close the figue. So far I have not found a way to close the figure after the user feedback was captured.

How do I close the figure (correctly), so I reach the end of the test and get my 'End of Test' statement?

function parent % outer function
disp('This is the outer function')
hkey = figure;
set(hkey,'KeyPressFcn',@UserFeedback);

disp('Make your choice: Press left or right arrow key')

waitfor(hkey);

UserFeedback

disp('End of Test')

    function UserFeedback(~,evnt) % inner function
       if strcmpi(evnt.Key,'leftarrow')
           disp('You chose option 1: leftarrow key.')
           close(hkey)
       elseif strcmpi(evnt.Key,'rightarrow')
           disp('You chose option 2: rightarrow key.')
           close(hkey)
       else
           disp('Invalid Key, please press left or right arrow key for evaluation.')
           return
       end

      disp('This was the inner function')
      
   end % inner function

end % outer function

[NbrOneProcastinator]

Simply delete the line after waitfor(hkey);

You cannot call UserFeedback here without any arguments. In general, why would you call UserFeedback here? The function has already been declared as KeyPressFunction of the figure further above.

[Jan]

@Brezelbayer: What is the problem with the shown code? Closing hkey looks correct, if hkey is a shared variable in a nested function. I'd prefer delete(hkey) but this might be a question of taste.

As W.J. said, it is unclear why you call UserFeedback() again.

[Brezelbayer]

Thanks! Deleting the call UserFeedback() solved the problem.

I was taught that if I have multiple nested functions the code looks more structured, if I call the functions first and define the functions at the end (see code below). Since in my case calling the function first was not purposeful, I guess I was simply mixing up something, because I'm still a Matlab beginner.

function outer_1()
% some initialization code
x = 2;
y = 4;
disp(sprintf('x=%d,y=%d',x,y));
% call inner_1:
inner_1()
    % a nested function
    function inner_1()
        disp('inner_1');
    end
    % another nested function
    function inner_2()
        disp('inner_2');
    end
end

Answer 1

[Benjamin Kraus]

As @W. J. stated, your code seems to run fine if you just remove the call to UserFeedback from after the call to waitfor.

Alternatively, have you tried the input function? It won't work if you need to capture left arrow and right arrow, but it does allow you to capture user input without needing to create a separate figure, or deal with KeyPressFcn or callbacks.

If you stick with your approach, you can clean-up your code a little by using the first input to UserFeedback, like this:

function askForUserFeedback % outer function
disp('This is the outer function')
hkey = figure;
set(hkey,'KeyPressFcn',@UserFeedback);
disp('Make your choice: Press left or right arrow key')
waitfor(hkey);
disp('End of Test')
    function UserFeedback(fig,evnt) % inner function
       if strcmpi(evnt.Key,'leftarrow')
           disp('You chose option 1: leftarrow key.')
           close(fig)
       elseif strcmpi(evnt.Key,'rightarrow')
           disp('You chose option 2: rightarrow key.')
           close(fig)
       else
           disp('Invalid Key, please press left or right arrow key for evaluation.')
           return
       end
      disp('This was the inner function')
   end % inner function
end % outer function