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 running 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

This is the Check_And_Load function.

• 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 fields 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 Open_Callback(hObject, eventdata, handles)
  [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(hObject, handles)
      end
  end
  

See the Creating Menus - The Menu Editor section for information on creating the menu.

Running the GUI

The Contact Name Callback