MATLAB SIMULINK 7 - GRAPHICAL USER INTERFACE Manuale Utente Scaricare il pdf (Pagina 194)

8 Programming the GUI

8-22

function checkbox1_Callback(hObject, eventdata, handles)

if (get(hObject,'Value') == get(hObject,'Max'))

% Checkbox is checked-take approriate action

else

% Checkbox is not checked-take approriate action

end

Edit Text

To obtain the string a user typed in an edit box, get the String property in the

the

Callback callback.

function edittext1_Callback(hObject, eventdata, handles)

user_string = get(hObject,'String');

% Proceed with callback

If the edit text Max and Min properties are set such that Max - Min > 1, the

user can enter multiple lines. For example, setting

Max to 2, with the default

value of

0 for Min, enables users to enter multiple lines.

Retrieving Numeric Data from an Edit Text Component

MATLAB returns the value of the edit text String property as a character

string. If you want users to enter numeric values, you must convert the

characters to numbers. You can do this using the

str2double command, which

converts strings to doubles. If the user enters nonnumeric characters,

str2double returns NaN.

You can use the following code in the edit text callback. It gets the value of the

String property and converts it to a double. It then checks whether the

converted value is

NaN (isnan), indicating the user entered a nonnumeric

character and displays an error dialog (

errordlg).

function edittext1_Callback(hObject, eventdata, handles)

user_entry = str2double(get(hObject,'string'));

if isnan(user_entry)

errordlg('You must enter a numeric value','Bad Input','modal')

end

% Proceed with callback...

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MATLAB SIMULINK 7 - GRAPHICAL USER INTERFACE Manuale Utente Pagina 194