Creating Graphical User Interfaces

Specifying the Directory to List

You can specify the directory to list when the GUI is first opened by passing the string 'create' and a string containing the full path to the directory as arguments. The syntax for doing this is list_box('create','dir_path'). If you do not specify a directory (i.e., if you call the GUI M-file with no input arguments), the GUI then uses the MATLAB current directory.

The default behavior of the GUI M-file that GUIDE generates is to run the GUI when there are no input arguments or to call a subfunction when the first input argument is a character string. This example changes this behavior so that you can call the M-file with

• No input arguments -- run the GUI using the MATLAB current directory.
• First input argument is 'create' and second input argument is a string that specifies a valid path to a directory -- run the GUI, displaying the specified directory.
• First input argument is not a directory, but is a character string and there is more than one argument -- execute the subfunction identified by the argument (execute callback).

The following code listing show the setup section of the GUI M-file, which does one the following:

• Sets the list box directory to the current directory, if no directory is specified.
• Changes the current directory, if a directory is specified.

• function lbox2_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 untitled (see VARARGIN)
  
  % Choose default command line output for lbox2
  handles.output = hObject;
  
  % Update handles structure
  guidata(hObject, handles);
  
  if nargin == 3,
      initial_dir = pwd;
  elseif nargin > 4
      if strcmpi(varargin{1},'dir')
          if exist(varargin{2},'dir')
              initial_dir = varargin{2};
          else
              errordlg({'Input argument must be a valid',...
                       'directory'},'Input Argument Error!')
              return
          end
      else
          errordlg('Unrecognized input argument',...
                   'Input Argument Error!');
          return;
      end
  end
  % Populate the listbox
  load_listbox(initial_dir,handles)
  

List Box Directory Reader

Loading the List Box

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