使用matlab的gui实现计算器时，如何解决小数点重复输入的问题

[weixin_48878679]

我在gui设计小数点的时候的出来的程序可以重复输入小数点，不知道怎么解决

[weixin_47327362]

% --- Executes on button press in decimal.
function decimal_Callback(hObject, eventdata, handles)
% hObject    handle to num1 (see GCBO)
% eventdata  reserved - to be defined in a future version of MATLAB
% handles    structure with handles and user data (see GUIDATA)
textString = get(handles.editshowresult,'String');
if textString(end)=='.'
    textString = textString;
else
    textString = strcat(textString,'.');
end
set(handles.editshowresult,'String',textString)