How to make a value limit condition to a edit text and slider in GUI?

I made a GUI that contains 1 slider (min=-180,max=180) and 1 edit text my goal is to have the user type the angle wanted in the edit text or instead use the slider to choose a value. but i found a problem: if the user typed a value bigger than 180 or smaller than -180, the slider vanishes.. I want to show a pop error window when that happens and reset the value of the edit text and the slider to max (or min) value .. I've wrote a code, but it seems that it's not working:

function Valeur_Theta1_Callback(hObject, eventdata, handles)
% hObject    handle to Valeur_Theta1 (see GCBO)
% eventdata  reserved - to be defined in a future version of MATLAB
% handles    structure with handles and user data (see GUIDATA)

% Hints: get(hObject,'String') returns contents of Valeur_Theta1 as text
%        str2double(get(hObject,'String')) returns contents of Valeur_Theta1 as a double
clear min max Theta1;
min=-180;max=180;
Theta1=str2double(get(handles.Valeur_Theta1,'string'));
if(Theta1>-180 || Theta1<180)
    {
        set(handles.Slider_Theta1,'value',Theta1);}
else if(Theta1<-180)
        {
        msgbox('Invalid Value', 'Error','error');
        set(handles.Slider_Theta1,'value',min);
        set(handles.Valeur_Theta1,'string',min);
        }
    else if(Theta1<-180)
        {
        msgbox('Invalid Value', 'Error','error');
        set(handles.Slider_Theta1,'value',max);
        set(handles.Valeur_Theta1,'string',max);
        }
        end
    end
end

please help!

Answer 1

[Image Analyst]

You DEFINITELY don't want to clear the min and max function!!!!!!! Not only that, but you go on to redefine them as something else. VERY DANGEROUS to redefine crucial built-in functions such as min() and max()!

Plus, it wasn't working because you used braces to stick the outputs of all your lines of code into a cell. Please read the FAQ on cells: http://matlab.wikia.com/wiki/FAQ#What_is_a_cell_array.3F. If you put braces around something, you're putting it into a cell. This is not C you know.

So just clip the values to -180 or +180 and carry on:

minSliderValue = get(handles.Slider_Theta1, 'Min');
maxSliderValue = get(handles.Slider_Theta1, 'Max');
if Theta1 < minSliderValue 
    Theta1 = minSliderValue ;
elseif Theta1 > maxSliderValue 
    Theta1 = maxSliderValue;
end
% Set slider value.
set(handles.Slider_Theta1, 'Value', Theta1);
% Set static text caption of slider.
caption = sprintf('Theta = %.2f', Theta1);
set(handles.Valeur_Theta1, 'String', caption);

Note I didn't use 180 or -180 anywhere, so this code is robust enough to handle any min or max that you might enter into GUIDE. If you did that and I had used 180, the code would break. This way is more robust because you only need to change the angle limits in one place and it carries through elsewhere.

Answer 2

[Med Aymane Ahajjam]

Appreciate your detailed answer Image Analyst :D I got it (and I read the FAQ ) and it works like charm! (y)