MATLAB SIMULINK 7 - GRAPHICAL USER INTERFACE Instrukcja Użytkownika Pobierz pdf (Strona 235)

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101

Callbacks for Specific Components

8-19

Change the Selected Item

When the end user selects an item, the pop-up menu’s Value property changes to a

number that corresponds to the item’s position in the menu. For example, a value of 1

corresponds to the first item in the list. If you want to change the selection in your UI

code, then change the Value property to another number between 1 and the number of

items in the menu.

For example, you can use the handles structure in GUIDE to access the pop-up menu

and change the Value property:

set(handles.popupmenu1,'Value',2)

The first argument, handles.popupmenu1, might be different in your code, depending

on the value of the pop-up menu Tag property.

Write the Callback Function

This code is an example of a pop-up menu callback function in GUIDE. Associate this

function with the pop-up menu Callback property to make it execute when the end user

selects an item from the menu.

function popupmenu1_Callback(hObject, eventdata, handles)

% hObject handle to popupmenu1 (see GCBO)

% eventdata reserved - to be defined in a future version of MATLAB

% handles structure with handles and user data (see GUIDATA)

% Hints: contents = cellstr(get(hObject,'String')) returns contents...

% contents{get(hObject,'Value')} returns selected item...

items = get(hObject,'String');

index_selected = get(hObject,'Value');

item_selected = items{index_selected};

display(item_selected);

When the end user selects an item in the pop-up menu, the callback function performs

the following tasks:

• Gets all the items in the pop-up menu and stores them in the variable, items.

• Gets the numeric index of the selected item and stores it in the variable,

index_selected.

• Gets the string value of the selected item and stores it in the variable,

item_selected.

• Displays the selected item in the MATLAB Command Window.

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