MATLAB SIMULINK 7 - GRAPHICAL USER INTERFACE Uživatelský manuál stáhnout pdf (Strana 237)

List Box Directory Reader

10-13

guidata(handles.figure1,handles)

set(handles.listbox1,'String',handles.file_names,...

'Value',1)

set(handles.text1,'String',pwd)

The List Box Callback

The list box callback handles only one case: a double-click on an item. Double

clicking is the standard way to open a file from a list box. If the selected item

is a file, it is passed to the

open command; if it is a directory, the GUI changes

to that directory and lists its contents.

Defining How to Open File Types

The callback makes use of the fact that the open command can handle a

number of different file types. However, the callback treats FIG-files

differently. Instead of opening the FIG-file, it passes it to the

guide command

for editing.

Determining Which Item the User Selected

Since a single click on an item also invokes the list box callback, it is necessary

to query the figure

SelectionType property to determine when the user has

performed a double click. A double-click on an item sets the

SelectionType

property to

open.

All the items in the list box are referenced by an index from

1 to n, where 1

refers to the first item and

n is the index of the nth item. MATLAB saves this

index in the list box

Value property.

The callback uses this index to get the name of the selected item from the list

of items contained in the

String property.

Determining if the Selected Item is a File or Directory

The load_listbox function uses the dir command to obtain a list of values

that indicate whether an item is a file or directory. These values (1 for

directory, 0 for file) are saved in the

handles structure. The list box callback

queries these values to determine if current selection is a file or directory and

takes the following action:

• If the selection is a directory — change to the directory (

cd) and call

load_listbox again to populate the list box with the contents of the new

directory.

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