MATLAB SIMULINK 7 - GRAPHICAL USER INTERFACE Instrukcja Użytkownika Pobierz pdf (Strona 196)

8 Programming the GUI

8-24

function listbox1_Callback(hObject, eventdata, handles)

index_selected = get(handles.listbox1,'Value');

list = get(handles.listbox1,'String');

item_selected = list{index_selected}; % Convert from cell array

% to string

Triggering Callback Execution

MATLAB executes the list box’s Callback callback after the mouse button is

released or after certain key press events:

• The arrow keys change the

Value property and trigger callback execution.

•

Enter and Space do not change the Value property but trigger callback

execution.

If the user double-clicks, the callback executes after each click. MATLAB sets

the figure’s

SelectionType property to normal on the first click and to open on

the second click. The callback can query the

SelectionType property to

determine if it was a single- or double-click.

List Box Examples

See the following examples for more information on using list boxes:

• “List Box Directory Reader” on page 10-9 — Shows how to creates a GUI that

displays the contents of directories in a list box and enables users to open a

variety of file types by double-clicking on the filename.

• “Accessing Workspace Variables from a List Box” on page 10-16 — Shows

how to access variables in the MATLAB base workspace from a list box GUI.

Pop-Up Menu

When the pop-up menu Callback callback is triggered, the pop-up menu Value

property contains the index of the selected item, where

1 corresponds to the

first item on the menu. The

String property contains the menu items as a cell

array of strings.

Using Only the Index of the Selected Menu Item

This example retrieves only the index of the item selected. It uses a switch

statement to take action based on the value. If the contents of the pop-up menu

1 2 ... 191 192 193 194 195 196 197 198 199 200 201 ... 329 330

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MATLAB SIMULINK 7 - GRAPHICAL USER INTERFACE Instrukcja Użytkownika Strona 196