Select file issue in Matlab GUI

In a GUI, I have a function that open a selected image file. I am trying to improve it that if an image is already shown in the axes it will give a question dialog box but it does not work. What is the problem? is there a better and nicer way to do it?

function loadImageButton_Callback(hObject, eventdata, handles)
% hObject    handle to loadImageButton (see GCBO)
% eventdata  reserved - to be defined in a future version of MATLAB
% handles    structure with handles and user data (see GUIDATA)

set(handles.imageAxes, 'Visible','off')

if exists(isappdata(0, 'IData'))  
 choice = questdlg('An image is already in process, open a new one?', ...
    'Load image', ...
    'Yes','No','No');
% Handle response
 switch choice
    case 'Yes'
  cla reset;
         [file, folder] = uigetfile({'*.jpg;*.gif;*.png;*.tif;*.bmp','All Image Files'},' Select image');
      if file == 0;
        return;
      end
      fullFileName = fullfile(folder, file);
      I = imread(fullFileName);
      setappdata(0,'IData',file);
    case 'No'
      return;
 end
else
   [file, folder] = uigetfile({'*.jpg;*.gif;*.png;*.tif;*.bmp','All Image Files'},' Select image');
   if file == 0;
    return;
   end
   fullFileName = fullfile(folder, file);
   I = imread(fullFileName);
   setappdata(0,'IData',file);
end

axes(handles.imageAxes);
imshow(I); 
setappdata(handles.imageAxes, 'yourVariable', I);

Answer 1

[Adam]

Declare

handles.hImage = [];
guidata( hObject, handles )

in your OpeningFcn

Then when you plot:

handles.hImage = imshow(...)
guidata( hObject, handles )

and to test if the image exists:

if ~isempty( handles.hImage ) && isgraphics( handles.hImage )
   ...
end

[Lluis Roca]

I added the Declarations in the OpeningFcn:

handles.hImage = [];
guidata( hObject, handles )

And changed the function loadImageButton_Callback to:

function loadImageButton_Callback(hObject, eventdata, handles)
% hObject    handle to loadImageButton (see GCBO)
% eventdata  reserved - to be defined in a future version of MATLAB
% handles    structure with handles and user data (see GUIDATA)

set(handles.imageAxes, 'Visible','off')

if ~isempty( handles.hImage ) && isgraphics( handles.hImage )
 choice = questdlg('An image is already in process, would you like top open a new one?', ...
    'Load image', ...
    'Yes','No','No');
% Handle response
 switch choice
    case 'Yes'
    cla reset;
         [file, folder] = uigetfile({'*.jpg;*.gif;*.png;*.tif;*.bmp','All Image Files'},' Select image');
      if file == 0;
        return;
      end
      fullFileName = fullfile(folder, file);
      I = imread(fullFileName);
      setappdata(0,'IData',file);
    case 'No'
      return;
 end
else
[file, folder] = uigetfile({'*.jpg;*.gif;*.png;*.tif;*.bmp','All Image Files'},' Select image');
if file == 0;
        return;
end
fullFileName = fullfile(folder, file);
I = imread(fullFileName);
setappdata(0,'IData',file);
end

axes(handles.imageAxes);
handles.hImage =imshow(I); 
guidata( hObject, handles )
setappdata(handles.imageAxes, 'yourVariable', I);

But it did not work, what is the error? Why did you advised to add:

handles.hImage = imshow(...)
guidata( hObject, handles )
and to change the if to:

if ~isempty( handles.hImage ) && isgraphics( handles.hImage )

[Adam]

"what is the error?"

I don't know, you didn't tell us what aspect of it didn't work.

The code I added saves the image handle when you plot it and then tests if that handle exists and is a valid graphics object.

[Lluis Roca]

You are right, the error is that when I re-click the button after selecting an image it does not give me the question dialog.