Creating Graphical User Interfaces

Loading an Address Book Into the Reader

There are two ways in which an address book (i.e., a MAT-file) is loaded into the GUI:

• When launching the GUI, you can specify a MAT-file as an argument. If you do not specify an argument, the GUI loads the default address book (addrbook.mat).
• The user can select Open under the File menu to browse for other MAT-files.

Validating the MAT-file

To be a valid address book, the MAT-file must contain a structure called Addresses that has two fields called Name and Phone. The Check_And_Load subfunction validates and loads the data with the following steps:

• Loads (load) the specified file or the default if none is specified.
• Determines if the MAT-file is a valid address book.
• Displays the data if it is valid. If it is not valid, displays an error dialog (errordlg).
• Returns 1 for valid MAT-files and 0 if invalid (used by the Open menu callback)
• Saves the following items in the handles structure:

The name of the MAT-file

The Addresses structure

An index pointer indicating which name and phone number are currently displayed

Check_And_Load Code Listing

Here is the listing for Check_And_Load.

function pass = Check_And_Load(file,handles)
% Initialize the variable "pass" to determine if this is a valid file.
pass = 0;
% If called without any file then set file to the default file name.
% Otherwise if the file exists then load it.
if isempty(file)
    file = 'addrbook.mat';
    handles.LastFile = file;
    guidata(handles.Address_Book,handles)
end
if exist(file) == 2
    data = load(file);
end
% Validate the MAT-file
% The file is valid if the variable is called "Addresses" and it has 
% fileds called "Name" and "Phone"
flds = fieldnames(data);
if (length(flds) == 1) & (strcmp(flds{1},'Addresses'))
    fields = fieldnames(data.Addresses);
    if (length(fields) == 2) &(strcmp(fields{1},'Name')) & 
(strcmp(fields{2},'Phone'))
        pass = 1;
    end
end
% If the file is valid, display it
if pass
    % Add Addresses to the handles structure
    handles.Addresses = data.Addresses;
    guidata(handles.Address_Book,handles)
    % Display the first entry
    set(handles.Contact_Name,'String',data.Addresses(1).Name)
    set(handles.Contact_Phone,'String',data.Addresses(1).Phone)
    % Set the index pointer to 1 and save handles
    handles.Index = 1;
    guidata(handles.Address_Book,handles)
else
    errordlg('Not a valid Address Book','Address Book Error')
end

The Open Menu Callback

The address book GUI contains a File menu that has an Open submenu for loading address book MAT-files. When selected, Open displays a dialog (uigetfile) that enables the user to browser for files. The dialog displays only MAT-files, but users can change the filter to display all files.

The dialog returns both the filename and the path to the file, which is then passed to fullfile to ensure the path is properly constructed for any platform. Check_And_Load validates and load the new address book.

Open_Callback Code Listing

function varargout = Open_Callback(h, eventdata, handles, varargin)
[filename, pathname] = uigetfile( ...
    {'*.mat', 'All MAT-Files (*.mat)'; ...
        '*.*','All Files (*.*)'}, ...
    'Select Address Book');
% If "Cancel" is selected then return
if isequal([filename,pathname],[0,0])
    return
% Otherwise construct the fullfilename and Check and load the file
else
    File = fullfile(pathname,filename);
    % if the MAT-file is not valid, do not save the name
    if Check_And_Load(File,handles)
        handles.LastFIle = File;
        guidata(h,handles)
    end
end

See the Menu Editor section for information on creating the menu.

Launching the GUI

The Contact Name Callback