MATLAB GUI: Update textbox when moving drawpoint

Question

I have a GUI where the user clicks a button to place a point (drawpoint). After placing the point, the Euclidean distance is calculated between it and a static point chosen prior.

I want to be able to move point created by the pushbutton; such that, after moving the point the Euclidean distance is recalculated and spit into a textbox.

I tried using addlistener (in the GUI_OpeningFcn postion) for the created point; however, I cannot figure out how to do this, as the handle doesn't exist until after the pushbutton is created.

Thus the issue: How can I dynamically perform a calculation and spit out the value upon moving a point? Below is the code for the pushbutton (which does what I want). But how can I recalculate after moving the point?

Perhaps, could this be down using WindowbuttonDownFcn? Again, just not sure how to incorporate this into the GUI.

% --- Executes on button press in pushbutton1.
function pushbutton1_Callback(hObject, eventdata, handles)
% hObject    handle to pushbutton1 (see GCBO)
% eventdata  reserved - to be defined in a future version of MATLAB
% handles    structure with handles and user data (see GUIDATA)

h = findobj('Name', 'N');
Ndata = guidata(h);

axes(Ndata.axes1);

mypoint = drawpoint;

handles.distx = mypoint.Position(1);
handles.disty = mypoint.Position(2);

xp = Ndata.xpix;
yp = Ndata.ypix;
handles.poix = abs(double(handles.distx) - double(Ndata.ISOx))/str2double(xp.String);
handles.poiy = abs(double(handles.disty) - double(Ndata.ISOy))/str2double(yp.String);

handles.poi = sqrt(handles.poix^2 + handles.poiy^2)+1.3;

set(handles.edit1, 'Value', handles.poi);
set(handles.edit1, 'String', num2str(handles.poi));

% Update handles structure
guidata(hObject, handles);

Answer 1

You can add the event listener after creating the point.

1. Create the point:

   mypoint = drawpoint;
   

2. Add event listener only if not exist (add it to handles):

   %Add event listenr only if not exist
   if ~isfield(handles, 'el')
       handles.el = addlistener(mypoint, 'ROIMoved', @mypointmoved_Callback);
   end
   

3. Update the edit box in the callback function:

   function mypointmoved_Callback(src, eventData)
   handles = guidata(src.Parent); %Get the handles using the parent of the point (the axes).
   handles.distx = src.Position(1);
   handles.disty = src.Position(2);
   set(handles.edit1, 'String', num2str(handles.distx)); %Simplified version of your code.
   drawnow
   

Here is a simplified version of the code (I put some of your code in comments):

% --- Executes on button press in pushbutton1.
function pushbutton1_Callback(hObject, eventdata, handles)
%h = findobj('Name', 'N');
%Ndata = guidata(h);

%axes(Ndata.axes1);
axes(handles.axes1);

mypoint = drawpoint;

%Add event listenr only if not exist
if ~isfield(handles, 'el')
    handles.el = addlistener(mypoint, 'ROIMoved', @mypointmoved_Callback);
end

handles.distx = mypoint.Position(1);
handles.disty = mypoint.Position(2);

% xp = Ndata.xpix;
% yp = Ndata.ypix;
% handles.poix = abs(double(handles.distx) - double(Ndata.ISOx))/str2double(xp.String);
% handles.poiy = abs(double(handles.disty) - double(Ndata.ISOy))/str2double(yp.String);

% handles.poi = sqrt(handles.poix^2 + handles.poiy^2)+1.3;

% set(handles.edit1, 'Value', handles.poi);
%set(handles.edit1, 'String', num2str(handles.poi));
set(handles.edit1, 'String', num2str(handles.distx));

% Update handles structure
guidata(hObject, handles);


function mypointmoved_Callback(src, eventData)
handles = guidata(src.Parent); %Get the handles using the parent of the point (the axes).
handles.distx = src.Position(1);
handles.disty = src.Position(2);
set(handles.edit1, 'String', num2str(handles.distx));
drawnow