Matlab: set default values for GUI edit text and use them in push button callback

I'm trying to initialize a GUI (built with GUIDE) with default values and then, if the user does not change the defaults, use these values in a function triggered by a push button callback.

To do this, inside the `_CreateFcn`, I first store the default values within the `handles`, then set the default of the GUI with `set(hObject, ...)` and finally update the guidata with `guidata(hObject, handles);`

If the user changes the value, I store the updated value in the handles inside the `_Callback` function reading the value with `get(hObject, ...)` and updating the guidata with `guidata(hObject, handles);`

When the button is pushed, inside the button `_Callback` function, I extract the value from the `handles`.

What happen is the following:

• if the user *does not* change the value on the GUI and simply pushes the button, what I read out from the variable stored in the handles is *not* the value of the variable, but the actual handle to the variable. This will return, for example: `27.0098876953125` or, for the newer versions -R2015b-:

    UIControl (ampmin) with properties:

              Style: 'edit'
             String: '1'
    BackgroundColor: [1 1 1]
           Callback: @(hObject,eventdata)GUI('ampmin_Callback',hObject,eventdata,guidata(hObject))
              Value: 0
           Position: [15.6000 14.6154 10.2000 1.6923]
              Units: 'characters'

    Use get to show all properties

• If, on the other hand, the user *does* change the value before pushing the button, then everything works fine and I get the actual variable value.

What am I missing?

UPDATE

I've noticed the following behavior:

• If I start the `.fig` file, the behavior is as expected
• If I start the `.m` file by pushing the `run` button, then I observe the strange behavior described above.

Here is the code (I've also attached a copy of the `.m` and `.fig` files):

    function varargout = GUI2(varargin)
    % GUI2 MATLAB code for GUI2.fig
    %      GUI2, by itself, creates a new GUI2 or raises the existing
    %      singleton*.
    %
    %      H = GUI2 returns the handle to a new GUI2 or the handle to
    %      the existing singleton*.
    %
    %      GUI2('CALLBACK',hObject,eventData,handles,...) calls the local
    %      function named CALLBACK in GUI2.M with the given input arguments.
    %
    %      GUI2('Property','Value',...) creates a new GUI2 or raises the
    %      existing singleton*.  Starting from the left, property value pairs are
    %      applied to the GUI2 before GUI2_OpeningFcn gets called.  An
    %      unrecognized property name or invalid value makes property application
    %      stop.  All inputs are passed to GUI2_OpeningFcn via varargin.
    %
    %      *See GUI2 Options on GUIDE Tools menu.  Choose "GUI2 allows only one
    %      instance to run (singleton)".
    %
    % See also: GUIDE, GUIDATA, GUIHANDLES

    % Edit the above text to modify the response to help GUI2

    % Last Modified by GUIDE v2.5 14-Aug-2015 10:39:46

    % Begin initialization code - DO NOT EDIT
    gui_Singleton = 1;
    gui_State = struct('gui_Name',       mfilename, ...
                       'gui_Singleton',  gui_Singleton, ...
                       'gui_OpeningFcn', @GUI2_OpeningFcn, ...
                       'gui_OutputFcn',  @GUI2_OutputFcn, ...
                       'gui_LayoutFcn',  [] , ...
                       'gui_Callback',   []);
    if nargin && ischar(varargin{1})
        gui_State.gui_Callback = str2func(varargin{1});
    end

    if nargout
        [varargout{1:nargout}] = gui_mainfcn(gui_State, varargin{:});
    else
        gui_mainfcn(gui_State, varargin{:});
    end
    % End initialization code - DO NOT EDIT

    % --- Executes just before GUI2 is made visible.
    function GUI2_OpeningFcn(hObject, eventdata, handles, varargin)
    % This function has no output args, see OutputFcn.
    % hObject    handle to figure
    % eventdata  reserved - to be defined in a future version of MATLAB
    % handles    structure with handles and user data (see GUIDATA)
    % varargin   command line arguments to GUI2 (see VARARGIN)

    % Choose default command line output for GUI2
    handles.output = hObject;

    % Update handles structure
    guidata(hObject, handles);

    % UIWAIT makes GUI2 wait for user response (see UIRESUME)
    % uiwait(handles.figure1);

    % --- Outputs from this function are returned to the command line.
    function varargout = GUI2_OutputFcn(hObject, eventdata, handles) 
    % varargout  cell array for returning output args (see VARARGOUT);
    % hObject    handle to figure
    % eventdata  reserved - to be defined in a future version of MATLAB
    % handles    structure with handles and user data (see GUIDATA)

    % Get default command line output from handles structure
    varargout{1} = handles.output;

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

    disp(handles.ampmin)

    function ampmin_Callback(hObject, eventdata, handles)
    % hObject    handle to ampmin (see GCBO)
    % eventdata  reserved - to be defined in a future version of MATLAB
    % handles    structure with handles and user data (see GUIDATA)

    % Hints: get(hObject,'String') returns contents of ampmin as text
    %        str2double(get(hObject,'String')) returns contents of ampmin as a double
    handles.ampmin = str2double(get(hObject,'String'));

    % Update handles structure
    guidata(hObject, handles);

    % --- Executes during object creation, after setting all properties.
    function ampmin_CreateFcn(hObject, eventdata, handles)
    % hObject    handle to ampmin (see GCBO)
    % eventdata  reserved - to be defined in a future version of MATLAB
    % handles    empty - handles not created until after all CreateFcns called

    % Hint: edit controls usually have a white background on Windows.
    %       See ISPC and COMPUTER.
    if ispc && isequal(get(hObject,'BackgroundColor'), get(0,'defaultUicontrolBackgroundColor'))
        set(hObject,'BackgroundColor','white');
    end

    handles.ampmin = 1.0;
    disp(handles.ampmin)
    set(hObject, 'String', num2str(handles.ampmin))

    % Update handles structure
    guidata(hObject, handles);

Answer 1

[Andrea Vaccari]

I actually found the issue. Buy using `handles.ampmin` as name of the variable I was effectively overwriting the `uicontrol` handle thus causing the described behavior. By changing the name of the variable to `handles.ampminvalue`, the behavior changed to the expected one.