Creating Graphical User Interfaces

Loading the List Box

This example uses a separate subfunction to load items into the list box. This subfunction accepts the path to a directory and the handles structure as input arguments. It performs these steps:

• Change to the specified directory so the GUI can navigate up and down the tree as required.
• Use the dir command to get a list of files in the specified directory and to determine which name is a directory and which is a file. dir returns a structure (dir_struct) with fields name and isdir, which contain this information.
• Sort the file and directory names (sortrows) and save the sorted names and other information in the handles structure so this information can be passed to other functions.

The name structure field is passed to sortrows as a cell array, which is transposed to get one file name per row. The isdir field and sorted_index are saved as vectors in the handles structure.

• Call guidata to save the handles structure.
• Set the list box String property to display the file and directory names and set the Value property to 1. This is necessary to ensure Value never exceeds the number of items in String, since MATLAB updates the Value property only when a selection occurs and not when the contents of String changes.
• Displays the current directory in the text box by setting its String property to the output of the pwd command.

The load_listbox function is called in the initialization section of the application M-file as well as the list box callback.

function load_listbox(dir_path,handles)
cd (dir_path)
dir_struct = dir(dir_path);
[sorted_names,sorted_index] = sortrows({dir_struct.name}');
handles.file_names = sorted_names;
handles.is_dir = [dir_struct.isdir];
handles.sorted_index = [sorted_index];
guidata(handles.figure1,handles)
set(handles.listbox1,'String',handles.file_names,'Value',1)
set(handles.text1,'String',pwd)

Specifying the Directory to List

The List Box Callback