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 full pathname as a string input argument. If you do not specify a directory (i.e., if you call the application M-file with no input arguments), the GUI then uses MATLAB's current directory.

As generated, the application M-file launches the GUI when there are no input arguments and calls 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 - launch the GUI using MATLAB's current directory.
• First input argument is a valid directory - launch 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 entire initialization section of the application M-file. The statements in bold are the additions made to the generated code:

function varargout = lbox2(varargin)
if nargin <= 1   % LAUNCH GUI
    if nargin == 0 
        initial_dir = pwd;
    elseif nargin == 1 & exist(varargin{1},'dir')
        initial_dir = varargin{1};
    else
        errordlg('Input argument must be a valid directory',...
            'Input Argument Error!')
        return
    end
    fig = openfig(mfilename,'reuse');
    % Use system color scheme for figure:
    set(fig,'Color',get(0,'defaultUicontrolBackgroundColor'));
    % Generate a structure of handles to pass to callbacks, and store it. 
    handles = guihandles(fig);
    guidata(fig, handles); 
    % Populate the listbox
    load_listbox(varargin{1},handles)
    if nargout > 0
        varargout{1} = fig;
    end
elseif ischar(varargin{1}) % INVOKE NAMED SUBFUNCTION OR CALLBACK
    try
        [varargout{1:nargout}] = feval(varargin{:}); % FEVAL switchyard
    catch
        disp(lasterr);
    end
end

List Box Directory Reader

Loading the List Box