Change color of the output string in GUI by command

I want to change the color of the output string by using popup menu. I have the command below but it seems to have some problems. Can anyone help me please.

function popupcolor_Callback(hObject, eventdata, handles)
% hObject    handle to popupcolor (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 popupcolor contents as cell array
%        contents{get(hObject,'Value')} returns selected item from popupcolor
switch get(handles.popupcolor, 'text')
    case 1
        set (handles.test_text, 'ForegroundColor', Red);
    case 2
        set (handles.test_text, 'ForegroundColor', Yellow);
    case 3
        set (handles.test_text, 'ForegroundColor', Purple);
    case 4
        set (handles.test_text, 'ForegroundColor', Blue);
    case 5
        set (handles.test_text, 'ForegroundColor', Green);
    otherwise
end

Answer 1

[Voss]

As far as I know there is no 'text' property of uicontrols. I think you mean to get the 'Value' property. That's one problem.

The second problem may be that Red, Yellow, etc., are not recognized variables or functions (or maybe they are functions you wrote - I cannot know), but I suspect you mean to use character color specifications (i.e., 'r', 'y', etc.). If this is the case, then you can try writing the callback like this:

function popupcolor_Callback(hObject, eventdata, handles)
% hObject    handle to popupcolor (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 popupcolor contents as cell array
%        contents{get(hObject,'Value')} returns selected item from popupcolor
switch get(handles.popupcolor, 'Value')
    case 1
        set (handles.test_text, 'ForegroundColor', 'r');
    case 2
        set (handles.test_text, 'ForegroundColor', 'y');
    case 3
        set (handles.test_text, 'ForegroundColor', 'm'); % magenta is like purple, right?
    case 4
        set (handles.test_text, 'ForegroundColor', 'b');
    case 5
        set (handles.test_text, 'ForegroundColor', 'g');
    otherwise
end

Or, if you want to be more flexible in case the set of colors listed in the popupmenu changes in the future (or the order changes, or the set of colors becomes something the user can control), you can avoid tying the behavior of the callback to the Value of the popupmenu and go by the text of the selected popupmenu item (like the Hints GUIDE puts there say). The approach below works for the common colors MATLAB supports specifying as a character ('r' 'g' 'b' 'c' 'm' 'y' 'k' 'w') and I've put in an exception to treat 'Purple' as magenta ('m'):

function popupcolor_Callback(hObject, eventdata, handles)
% hObject    handle to popupcolor (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 popupcolor contents as cell array
%        contents{get(hObject,'Value')} returns selected item from popupcolor

contents = cellstr(get(handles.popupcolor,'String'));
str = contents{get(handles.popupcolor,'Value')};

if strcmp(str,'Purple')
    str = 'Magenta';
end
set(handles.test_text, 'ForegroundColor', lower(str(1)));