MATLAB GUIDE button must be pressed twice? - matlab

Question

I'm making a GUI with guide. I have a push button the user clicks and the callback is as folows : (what matters are the tirst two lines really...
function SetParticleRoiSize_Callback(hObject, eventdata, handles)
% hObject handle to SetParticleRoiSize (see GCBO)
% eventdata reserved - to be defined in a future version of MATLAB
% handles structure with handles and user data (see GUIDATA)
handles=guidata(hObject);
particleroiSize=imrect;% - draw a rectagle around the particle to get a meausr eof ROI size
roiPoints=getPosition(particleroiSize); %-get tha parameters fo the rectanlge
partX1 = round(roiPoints(1));
partY1 = round(roiPoints(2));
partX2 = round(partX1 + roiPoints(3));
partY2 = round(partY1 + roiPoints(4)); % these are the ROi positions in pixels
roiHeight = round(roiPoints(3)); % - these are just the ROI width and height
roiWidth = round(roiPoints(4));
handles=guidata(hObject); %_ update all the handles...
handles.partX1=partX1;
handles.partX2=partX2;
handles.partY1=partY1;
handles.partY2=partY2;
handles.roicenterX = (partX1 + round(roiPoints(3))/2);
handles.roicenterY= (partY1 + round(roiPoints(4))/2);
handles.roiHeight = roiHeight;
handles.roiWidth = roiWidth;
current_slice = round(get(handles.Image_Slider,'Value'));
handles.current_slice=current_slice;
particleImage=handles.Image_Sequence_Data(partY1:partY2,partX1:partX2,current_slice);
handles.particleImage=particleImage;
set(handles.RoiSizeDisplay,'String',['Particle ROI is ',' ',num2str(roiHeight),' ', ' by ',num2str(roiWidth)] );
guidata(hObject,handles); %- at this point we now have the particle in the roi and the size of the roi stored.
The issue I am having is that when the user clicks the button the first time, nothing happens (i.e. the imrect line seems to not get called at all). When the user clicks the button again then they can draw a rectangle on the image but my program throws out an error
Error in imrect (line 83)
[h_group,draw_api] = imrectAPI(varargin{:});
Error in SemiAutomated_Fionv2p2_5>SetParticleRoiSize_Callback (line 291)
particleroiSize=imrect;% - draw a rectagle around the particle to get a meausr eof ROI size
Error in gui_mainfcn (line 96)
feval(varargin{:});
Error in SemiAutomated_Fionv2p2_5 (line 56)
gui_mainfcn(gui_State, varargin{:});
Error in
#(hObject,eventdata)SemiAutomated_Fionv2p2_5('SetParticleRoiSize_Callback',hObject,eventdata,guidata(hObject))
Error while evaluating uicontrol Callback
I guess the error is because there is no imrect created on the first button click.
Can someone please explain to me why this button needs to be clicked twice to work? (and even then it still gives an error...)
thanks...
-j

Answer 1

It looks like this call:
handles=guidata(hObject); %_ update all the handles...
is incorrectly used; you might need to replace it with guidata(hObject,handles) in order to actually update the handles structure. Moreover, since you already call guidata(hObject,handles) at the end of the callback you can delete this line altogether I think.
As it's currently implemented, you:
1) get the handles structure with handles = guidata(hObject);
2) store information in it
particleroiSize=imrect;% - draw a rectagle around the particle to get a meausr eof ROI size
roiPoints=getPosition(particleroiSize); %-get tha parameters fo the rectanlge
partX1 = round(roiPoints(1));
partY1 = round(roiPoints(2));
partX2 = round(partX1 + roiPoints(3));
partY2 = round(partY1 + roiPoints(4)); % these are the ROi positions in pixels
roiHeight = round(roiPoints(3)); % - these are just the ROI width and height
roiWidth = round(roiPoints(4));
3) then call it again (handles = guidata(hObject))`.
Hence on your second call to retrieve the data you have not previously updated it, so I guess Matlab does not like it.
It might not be the specific cause of your error but I think it's worth checking.

Answer 2

I had 3 different axes in my figure. The first version of the program only had 1 axes so it worked fine. After adding the other axes to the GUI (via GUIDE) when I ran just imrect.. I think it was not choosing the axes I wanted..I added a parent handles.correct axes and now it works perfectly!