KeyPressFcn and WindowKeyPressFcn not working

I have a GUI (using the old figure, not uifigure). The figure has a KeyPressFcn to do some action.

So I have a pushbutton, and after clicking it I want to hide the button, so its callback turns off its visibility ('Visible', 'off').

When that happens, the KeyPressFcn (or WindowKeyPressFcn I also tried it) if the figure stops working. No matter what I do, I can't recover the focus.

So this is what I tried, and nothing worked, even with everything combined:

set(figHandle, 'CurrentObject', figHandle)
set(figHandle, 'CurrentObject', pushbuttonHandle)
figure(figHandle)
gco(figHandle)
gcf(figHandle)
figHandle.Visible = 'off'
figHandle.Visible = 'on'
drawnow

NOTHING WORKS.

Only way to make it work again is clicking the figure. But thats exactly what I DONT want to do. I must not click the figure after clicking the pushbutton, at least before the desired keypress.

However, if I enter debubg mode using breakpoints, then this works:

set(figHandle, 'CurrentObject', figHandle)
figure(figHandle)

But it does not work if not in debug mode. I don't understand this behaviour. I know removing visbility to objects have some strange side effects. But it should never remove permanently focus from a figure.

Why does it work in debugging mode, but not in normal mode?

Matlab R2020b

[Voss]

Rather than setting the pushbutton invisible in its callback, try setting its position to something outside the figure, e.g., [-10 -10 1 1], and see if that changes anything.

[André]

Its a possible option, maybe I will test it later.

I ended up using virtual mouse clicks using Java to recover the focus of the figure. I don't like such clumsy solutions, but thats the only way I figured out.

Answer 1

[Divyajyoti Nayak]

Hi @André,

From what I understand, you want the focus to come back to the parent figure after the button has been clicked, this should give the desired functionality. I could not find any direct function that restores focus to the figure like the ‘focus’ function which works for ‘uifigure’ but I did find a work around.

Here’s a sample code to help you out:

• Initial setup of the GUI

f = figure; 
f.KeyPressFcn = @keyPress; 
btn = uicontrol(f,'Style','pushbutton','String','Hide','Callback',@btnCallback); 

function btnCallback(src, event) 
    src.Visible = 'off'; 

• The ‘set’ function can be used to set the ‘enable’ property to ‘off’ which disables the button. This removes the focus from the button.

    set(src, 'Enable', 'off'); 

• ‘drawnow’ updates the figure bringing the focus back onto it

    drawnow update; 

• If the button is still needed, it can be enabled without losing focus from the figure using the ‘set’ function again:

    set(src, 'Enable', 'on'); 
end 

function keyPress(src,event) 
disp("key pressed"); 
end 

For more information on this workaround, you can check out this MATLAB Answer post:

https://www.mathworks.com/support/search.html/answers/33224-gui-figure-focus.html

[André]

Seems to do the trick. I was using Java to simulate mouse clicks and get focus, but it was far from perfect...