App Designer MATLAB: if-else condition not working

I am creating a GUI in App Designer (version: MATLAB R2022b).

I have a first function configured which allows users to Load an image in the GUI (important part of the code: I transform the value of another button on the app, the StatebuttonButton, to 1 at the end of the function exection):

function LoadimageButtonPushed(app, event)

[filename,filepath]=uigetfile({'*.jpg;*.tif;*.png;*.gif;*.bmp','All Image Files'},'Select an image');

fullname=[filepath, filename];

ImageFile=imread(fullname);

imagesc(app.UIAxes_3, ImageFile);

app.StatebuttonButton.Value = 1;

end

Then a second function that should allow users to crop the image loaded above. However, I want to make sure that an image was loaded by the user in the first place (before pushing the crop button), so I have configured the if-else statement below to do so. Based on the "Value" of app.StatebuttonButton, it should know whether an image was loaded in the first place:

function CropButtonPushed(app, event)

if not(app.StatebuttonButton.Value == 1)

f=errordlg('Please load an image first','User Action Error');

else

;

end

% rest of function

% rest of function

end

The problem is that the if-else statement is not working, and I am not even receiving any error from MATLAB explaining why.

Can someboy help?

Answer 1

[Hiro Yoshino]

I found a solution for this.

errordlg is not suitable for App Designer; you should use uialert instead. There is a small note at the bottom of the errordlg document and it says use "uialert" in the case of app building.

Hope this helps.

Answer 2

[Hiro Yoshino]

What is the default value for app.StatebuttonButton.Value? Have you checked it in the first place?

If it is "1", it always skip the if condition even when you haven't uploaded any images.

[Makram]

Thanks for your comment, I did a quick check, and it appeared that the default value of app.StatebuttonButton is "0", and after I assign it to 1, app.StatebuttonButton.Value becomes "1".

This is then not the source of the problem unfortunately.

[Hiro Yoshino]

How about using a "break point" just before

if not(app.StatebuttonButton.Value == 1)

to see what app.StatebuttonButton.Value is there?

[Makram]

Thanks for the help. I ended up finding a better solution, I made the "cropbutton" invisible when the app is started, and then only when an image is loaded I make it visible.

[N/A]

Indeed! Thanks for your help.