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8 Programming the GUI

8-8

Associating Callbacks with Components

A GUI can have many components and GUIDE provides a way of specifying

which callback should run in response to a particular event for a particular

component. The callback that runs when the user clicks a

Yes button is not the

one that runs for the

No button. Each menu item usually performs a different

function.

GUIDE uses each component’s callback properties to associate specific

callbacks with that component. This topic tells you how GUIDE can

automatically set the values of callback properties.

Note “Kinds of Callbacks” on page 8-2 provides a list of callback properties

and the components to which each applies.

Setting Callback Properties Automatically

GUIDE initially sets the value of the most commonly used callback properties

for each component to

%automatic. For example, a push button has five

callback properties,

ButtonDownFcn, Callback, CreateFcn, DeleteFcn, and

KeyPressFcn. GUIDE sets only the Callback property, the most commonly

used callback, to

%automatic. You can use the Property Inspector to set the

other callback properties to

%automatic.

When you next save the GUI, GUIDE replaces

%automatic with a MATLAB

expression that is the GUI calling sequence for the callback. Within the calling

sequence, it constructs the callback name, i.e., the subfunction name, from the

component’s

Tag property and the name of the callback property. The following

figure shows an example of a push button’s

Callback and Tag properties in the

GUIDE Property Inspector before the GUI is saved.

Note If you change the string %automatic before saving the GUI, GUIDE

does not automatically add a callback for that component or menu item.

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MATLAB SIMULINK 7 - GRAPHICAL USER INTERFACE Manuale Utente Pagina 180