Adding a button which activates ginput to give values

Hi there, I have been having some issues trying to add buttons and calling functions and functions handles. This is what I had...

   but=uicontrol('Style', 'pushbutton',...
            'String', 'Pick Maximum Trace',...
            'Position', [10 10 200 20]);
   set(but,'Callback',{'pick',p});

Seperate file...

function  [x,y]=pick(hObj,event,p) %#ok<INUSD

[x,y]=ginput(p);

end

The problem is trying to get out the x and y variables from the pick function. How do I get output variables from a callback?

Cheers for the help, James

Answer 1

[Jan]

Where do you want to get these outputs?

You can store them e.g. in the GUI's UserData or by GUIDATA:

function pick(hObj, event, p)
  [x,y]=ginput(p);
  FigH = ancestor(hObj, 'figure');
  set(FigH, 'UserData', [x, y]);
  % Or:
  setappdata(FigH, 'LastPoint', [x, y]);
  % Or:
  handles = guidata(FigH);
  handles.InputPoint = [x, y];
  guidata(FigH, handles);
end

The methods to get these values later are similar: get(FigH, 'UserData'), or getappdata, or the GUIDATA approach.

[James]

All I'm trying to do is call the ginput, pick function and get the values of x and y out to use else where in the script like a normal function or sub-routine

so ideally something like

[x,y]=set(but,'Callback',{'pick',p});

but that doesn't work...I'll try your ideas Cheers

Answer 2

[Matt Fig]

One approach would be to make the callback for your button a function in the GUI file which immediately calls the PICK function.

function [] = mybuttoncallback(varargin)
% Callback for button.
[x,y] = pick(...)
% Now save in GUIDATA or whatever...

Then you have your x and y in this workspace to save to the appdata with GUIDATA or whatever. This gives you more control over the callback, as you can use try-catch in searching for the PICK file.

The other alternative is to forget about the PICK function altogether and just put the call to GINPUT directly into the callback which is in the GUI file.