Accessing ROI objects in GUIDE

I'm allowing the user to create a series of line ROIs like so, using a GUIDE app pushbutton:

function pushbuttonline_Callback(hObject, eventdata, handles)
% hObject    handle to linebtn (see GCBO)
% eventdata  reserved - to be defined in a future version of MATLAB
% handles    structure with handles and user data (see GUIDATA)
h = drawline(handles.axes1);

But how can I access these later on in the code?

I was thinking of placing the drawline variables in a global array, but is there a better way of doing this?

Also, if the user deleted a line using the GUI, would the line variable also be removed?

Thanks in advance.

Answer 1

[Adam Danz]

This demo works outside of your GUI callback but it will be easy to implement it into your GUI. See inline comments for details.

% Create axes (your gui will already have axes)
handles.axes1 = axes(); 

% Draw 3 lines (your gui will only have 1 of these lines 
% but it's important to add the 'Tag' to your line.
% The tag name should be something unique - I chose 'userLine'. 
h = drawline(handles.axes1,'Tag','userLine'); 
h = drawline(handles.axes1,'Tag','userLine'); 
h = drawline(handles.axes1,'Tag','userLine'); 

% Later on from any other callback function that has 
% access to 'handles', you can find all objects in 
% your axes that has that tag.  If 'lineHandles' is
% empty, no objects were found with that tag. Otherwise
% 'lineHandles' will contain all of the handles to your
% ROI lines.
lineHandles = findobj(handles.axes1,'Tag','userLine')

[John D]

If I wanted to access the axes through a function that wasn't a callback (i.e. didn't have the 'handles' parameter), how would I go about doing that? For example, the allevents function:

function linebtn_Callback(hObject, eventdata, handles)
% hObject    handle to linebtn (see GCBO)
% eventdata  reserved - to be defined in a future version of MATLAB
% handles    structure with handles and user data (see GUIDATA)
h = drawline(handles.axes1,'Tag','userLine');
addlistener(h,'ROIMoved',@allevents);

function allevents(src,evt)
evname = evt.EventName;
switch(evname)
    case{'ROIMoved'}
        % here ------------
end

Thanks.

[Adam Danz]

The only handle you really need is the axis handle handles.axes1

I don't know what is calling the allevents function so I can't guess what the src handle is.

A common way to find an axes is to use findobj(). For example, let's say you press a button that triggers allevents(). The parent of the button is the main GUI figure and your axes is also a child of the main GUI figure. If the button handle is 'h' you could find the axes using

ax = findobj(h.Parent,'type','axes')

assuming the GUI only has 1 axes (otherwise all axes handles would be returned).

[John D]

Ok, I see. I suppose, to combat the error of having multiple axes, you could do this?

ax = findobj(h.Parent,'Tag','axes1')

[Adam Danz]

Yes, as long as you've assigned "axes1" to the tag property of that axes!

[Adam Danz]

Better yet,

ax = findobj(h.Parent,'Type','axes','Tag','axes1')

When using findobj() or findall() you want to be as specific as possible.

[John D]

Thanks!