GUI - 'Struct contents reference from a non-struct array object' error.

Hi, I am part way through making a GUI for batch image processing. I have a listbox (listbox1) and a pushbutton (PUSHBUTTON1). The pushbutton1 is used for 'browsing' through my files to choose a folder and load the contents of that folder (a selection of images) to display on the listbox1. I click the 'browse' pushbutton and sure enough, it takes me to my files, but when I select the folder I want I get this error:

MyListOfFiles = 

    Columns 1 through 7

      'IMG_1383.JPG'    'IMG_1384.JPG'    'IMG_1385.JPG'    'IMG_1386.JPG'    'IMG_1387.JPG'    'IMG_1388.JPG'    'IMG_1389.JPG'

    Columns 8 through 14

      'IMG_1390.JPG'    'IMG_1391.JPG'    'IMG_1392.JPG'    'IMG_1393.JPG'    'IMG_1394.JPG'    'IMG_1395.JPG'    'IMG_1396.JPG'

    Columns 15 through 21

      'IMG_1397.JPG'    'IMG_1398.JPG'    'IMG_1399.JPG'    'IMG_1400.JPG'    'IMG_1401.JPG'    'IMG_1402.JPG'    'IMG_1403.JPG'

    Columns 22 through 28

      'IMG_1404.JPG'    'IMG_1405.JPG'    'IMG_1406.JPG'    'IMG_1407.JPG'    'IMG_1408.JPG'    'IMG_1409.JPG'    'IMG_1410.JPG'

    Columns 29 through 34

      'IMG_1411.JPG'    'IMG_1412.JPG'    'IMG_1413.JPG'    'IMG_1414.JPG'    'IMG_1415.JPG'    'Whole_Trial_1_CAT…' 

Struct contents reference from a non-struct array object.

Error in GUI_2>pushbutton1_Callback (line 112)
set(handles.listbox1,'String', MyListOfFiles);

Error in gui_mainfcn (line 95)
        feval(varargin{:});

Error in GUI_2 (line 42)
    gui_mainfcn(gui_State, varargin{:});

Error in matlab.graphics.internal.figfile.FigFile/read>@(hObject,eventdata)GUI_2('pushbutton1_Callback',hObject,eventdata,guidata(hObject))

Error while evaluating UIControl Callback

So, as the files are displayed to my command window, it must be working, just not displaying them to my listbox and I can't figure out why! I suspect it is a problem with the 'handles' but I cant figure it out. Here is ALL my GUI code so far:

    function varargout = GUI_2(varargin)
    %GUI_2 M-file for GUI_2.fig
    %      GUI_2, by itself, creates a new GUI_2 or raises the existing
    %      singleton*.
    %
    %      H = GUI_2 returns the handle to a new GUI_2 or the handle to
    %      the existing singleton*.
    %
    %      GUI_2('Property','Value',...) creates a new GUI_2 using the
    %      given property value pairs. Unrecognized properties are passed via
    %      varargin to GUI_2_OpeningFcn.  This calling syntax produces a
    %      warning when there is an existing singleton*.
    %
    %      GUI_2('CALLBACK') and GUI_2('CALLBACK',hObject,...) call the
    %      local function named CALLBACK in GUI_2.M with the given input
    %      arguments.
    %
    %      *See GUI Options on GUIDE's Tools menu.  Choose "GUI allows only one
    %      instance to run (singleton)".
    %
    % See also: GUIDE, GUIDATA, GUIHANDLES

    % Edit the above text to modify the response to help GUI_2

    % Last Modified by GUIDE v2.5 02-Mar-2016 16:10:54

    % Begin initialization code - DO NOT EDIT
    gui_Singleton = 1;
    gui_State = struct('gui_Name',       mfilename, ...
                       'gui_Singleton',  gui_Singleton, ...
                       'gui_OpeningFcn', @GUI_2_OpeningFcn, ...
                       'gui_OutputFcn',  @GUI_2_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 GUI_2 is made visible.
    function GUI_2_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   unrecognized PropertyName/PropertyValue pairs from the
    %            command line (see VARARGIN)

    % Choose default command line output for GUI_2
    handles.output = hObject;

    % Update handles structure
    guidata(hObject, handles);

    % UIWAIT makes GUI_2 wait for user response (see UIRESUME)
    % uiwait(handles.figure1);

    % --- Outputs from this function are returned to the command line.
    function varargout = GUI_2_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 selection change in listbox1.
    function listbox1_Callback(hObject, eventdata, handles)
    % hObject    handle to listbox1 (see GCBO)
    % eventdata  reserved - to be defined in a future version of MATLAB
    % handles    structure with handles and user data (see GUIDATA)

    % Hints: contents = cellstr(get(hObject,'String')) returns listbox1 contents as cell array
    %        contents{get(hObject,'Value')} returns selected item from listbox1

    % --- Executes during object creation, after setting all properties.
    function listbox1_CreateFcn(hObject, eventdata, handles)
    % hObject    handle to listbox1 (see GCBO)
    % eventdata  reserved - to be defined in a future version of MATLAB
    % handles    empty - handles not created until after all CreateFcns called

    % Hint: listbox 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

    % --- 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)
     % --- Load up the listbox with tif files in folder handles.handles.ImageFolder

    % get the folder
    folder_name = uigetdir;
    % get what is inside the folder
    Infolder = dir(folder_name);
    MyListOfFiles = {Infolder(~[Infolder.isdir]).name}
    set(handles.listbox1,'String', MyListOfFiles);

    % --- Executes on button press in pushbutton2.
    function pushbutton2_Callback(hObject, eventdata, handles)
    % hObject    handle to pushbutton2 (see GCBO)
    % eventdata  reserved - to be defined in a future version of MATLAB
    % handles    structure with handles and user data (see GUIDATA)
    [file,path]=uiputfile('*.jpg','Save Destination');

    % --- Executes on button press in pushbutton3.
    function pushbutton3_Callback(hObject, eventdata, handles)
    % hObject    handle to pushbutton3 (see GCBO)
    % eventdata  reserved - to be defined in a future version of MATLAB
    % handles    structure with handles and user data (see GUIDATA)

    % --- Executes on button press in pushbutton4.
    function pushbutton4_Callback(hObject, eventdata, handles)
    % hObject    handle to pushbutton4 (see GCBO)
    % eventdata  reserved - to be defined in a future version of MATLAB
    % handles    structure with handles and user data (see GUIDATA)
    msgbox('Thankyou for using the Image Processing Tool');
    pause(3);
    close();
    close();

    % --- Executes on selection change in listbox2.
    function listbox2_Callback(hObject, eventdata, handles)
    % hObject    handle to listbox2 (see GCBO)
    % eventdata  reserved - to be defined in a future version of MATLAB
    % handles    structure with handles and user data (see GUIDATA)

    % Hints: contents = cellstr(get(hObject,'String')) returns listbox2 contents as cell array
    %        contents{get(hObject,'Value')} returns selected item from listbox2

    % --- Executes during object creation, after setting all properties.
    function listbox2_CreateFcn(hObject, eventdata, handles)
    % hObject    handle to listbox2 (see GCBO)
    % eventdata  reserved - to be defined in a future version of MATLAB
    % handles    empty - handles not created until after all CreateFcns called

    % Hint: listbox 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

    function edit2_Callback(hObject, eventdata, handles)
    % hObject    handle to edit2 (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 edit2 as text
    %        str2double(get(hObject,'String')) returns contents of edit2 as a double

    % --- Executes during object creation, after setting all properties.
    function edit2_CreateFcn(hObject, eventdata, handles)
    % hObject    handle to edit2 (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

So, if anyone can please help I would be very grateful.

Cheers, Ellis

Answer 1

[Geoff Hayes]

Ellis - put a breakpoint at the line of code that is generating the error

 set(handles.listbox1,'String', MyListOfFiles);

Now repeat your steps. Launch the GUI (from the command line or by pushing the Run button in the editor) and press the pushbutton to select your folder. Now when the debugger pauses at the above line of code, look at the handles structure. Does it have a field named listbox1? The error message is indicating that this field doesn't exist. From your posted code, there are callbacks for a listbox1 but there are also callbacks for a listbox2. Did you perhaps delete the first one but not the callbacks for it? Does your GUI have two listboxes?

(I have tested your lines of code to populate the listbox and it works fine. )

[Ellis Berry]

There are meant to be two listbox's yes. I haven't got up to fiddling with the second one yet, but that is where I want the processed images to appear.

[Ellis Berry]

Hi Geoff, thanks for your answer. I did as you said and I got it to work now fine with no errors! Thankyou very much.

[William Chamberlain]

Hi Ellis; would be stoked if you could post your fixed code, so I can see what you had to change.

Answer 2

[Luis Fernando Hoyos Cogollo]

This could work

https://www.mathworks.com/matlabcentral/answers/304835-gui-error-struct-contents-reference-from-a-non-struct-array-object#answer_236524