How to automtically update editText box with 'new axes limit' when Zoom tool has changed the axes limit?

I am looking at an example with zoom given in Matlab help:

function demo
% Listen to zoom events
plot(1:10);
h = zoom;
set(h,'ActionPostCallback',@mypostcallback);
set(h,'Enable','on');
%
function mypostcallback(obj,evd)
newLim = get(evd.Axes,'XLim');
msgbox(sprintf('The new X-Limits are [%.2f %.2f].',newLim));
----------------------------------------------

How would I update an existing editText box with the newLim from within mypostcallback()? Or would I have to create an event listener? Then how would I do that?

[betty bowles]

I am trying to use this with the toolbar zoom using guide. Do I need to overwrite the callback function in order to set the 'ActionPostCallback' to respond with @mypostcallback? If so, I am not sure what the default callback on the tool does other than call zoom(). Please advise.

Answer 1

[Geoff Hayes]

betty - I don't think that you need an event listener, you just need the means at which to access the handle to the edit text control. From the above example, you haven't indicated how you are using this code or how you have created your GUI, but let's assume that you have done so with GUIDE. Suppose that you have an axes, a (say) checkbox to enable or disable the zoom, and a text box to display the axes limits. Then in the checkbox callback we enable or disable the zoom as

 function checkbox1_Callback(hObject, eventdata, handles)
 if get(hObject,'Value') == 1
    if ~isfield(handles,'hZoom')
        handles.hZoom = zoom;
        set(handles.hZoom,'ActionPostCallback',@zoomPostCallback);
        guidata(hObject,handles);
    end
    set(handles.hZoom,'Enable','on');
 else
    if isfield(handles,'hZoom')
        set(handles.hZoom,'Enable','off');
    end
 end

In the zoom post action callback we do

 function zoomPostCallback(hObject,event)
 handles = guidata(hObject);
 if isfield(handles,'text1')
    set(handles.text1,'String',num2str(get(handles.axes1,'XLim')));
 end

In the above, we use the hObject input parameter to get the handles structure (via guidata) which will have the handle to the text1 control. We update that control using the new limits of axes1. See the attached for a simple example.

[betty bowles]

thank geoff, it was the @zoomPostCallback() input argument 'hObject' i hadn't connected the dots with. so I assume you could still use the 'event' input argument to access the 'Axes.xLim'?

[Geoff Hayes]

Yes, you could still use the event object.