Multiple GUI points with addlisteners

Question

I have a GUI, where the user clicks a button to create a point. This point is used for measurements (i.e. calculating the distance between it and another static point).

    function pushbutton1_Callback(hObject, eventdata, handles)

    a = handles.calciter; % This iterates for each time pushbutton is pressed.

    mypoint = drawpoint(handles.axes1);

    handles.el = addlistener(mypoint, 'ROIMoved', @mypointmoved_Callback);

So if my pushbutton1 creates another point; how can I have it so there are multiple addlistener for each of the points?

Do I need to have multiple handles.el?

My previous question contains a bit more info if interested.

Answer 1

Continuation of my previous answer...

• Add a listener to every new point.
• You don't need to need to have multiple handles.el, you can just ignore el because you are not using it anyway.
• You can store an array of handles of created points (if you need it).
• You can store the index of the point in mypoint.UserData (if you need it).
• In the listener's callback, you can get any point from the array, and also check the index of the points that triggered the event.

Here is the relevant parts of the code (please read the comments):

% --- Executes on button press in pushbutton1.
function pushbutton1_Callback(hObject, eventdata, handles)
axes(handles.axes1);

mypoint = drawpoint;

%Add event listenr to every point
%if ~isfield(handles, 'el')
addlistener(mypoint, 'ROIMoved', @mypointmoved_Callback);
%end

%Save an array of handles to created points:
if ~isfield(handles, 'mypoints')
    mypoint.Color = [0.7410, 0.2, 0]; %First point has a different color.
    handles.mypoints = mypoint; %Add first point.

    %Distance from the first added point.
    handles.distx = 0;
    handles.disty = 0;
    set(handles.edit1, 'String', '0'); %Display the distance from the first added point.
else    
    handles.mypoints(end+1) = mypoint; %Add a new point to the end of the array
end

points_counter = length(handles.mypoints); %Number of points - use as "Point serial number".
mypoint.UserData = points_counter; %Store the index of the point in UserData property

% 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).

if src.UserData == 1
    %Example for using the index of the point stored in UserData property.
    set(handles.edit1, 'String', '0');
    return;
end

px = src.Position(1);
py = src.Position(2);

%Get the first point that added by the user 
p0 = handles.mypoints(1);

%Get the x,y position of the first point that added by the user
p0x = p0.Position(1);
p0y = p0.Position(2);

%Compute the distance from p0:
distx = abs(px - p0x);
disty = abs(py - p0y);

handles.distx = distx;
handles.disty = disty;

dist = norm([distx, disty]); %Euclidean distance

%Display the euclidean distance from p0.
set(handles.edit1, 'String', num2str(dist));
drawnow

The example displays the euclidean distance of the point that moved by the user to the first point added (by the user).