如何獲得從回調函數中輸入的前一個值？

Question

我知道這可能是一個簡單的問題，但我是Matlab GUI的新手，基本上想要獲得原來存儲在文本框中的值，以替換剛剛輸入的值。例如。

1. 文本框中包含一個有效的字符串，
2. 用戶輸入無效的字符串，
3. 回調FUNC，驗證輸入，實現了新的輸入錯誤並且恢復到舊的前值。

這應該如何實施或完成？ Atm我只是使用get和set屬性值。 下面是一些示例代碼：

function sampledist_Callback(hObject, eventdata, handles) 
% hObject handle to sampledist (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 sampledist as text 
%  str2double(get(hObject,'String')) returns contents of sampledist as a double 

input = str2double(get(hObject,'String')); 
if(input < 0 || input > 500) 
    errordlg('Sampled Dist. must be > 0 and < 500','Sample Dist - Input Error'); 
    set(handles.sampledist,'String',['10']); %<--- I would like this value 10 to be the previous entry! 
    guidata(hObject,handles); 
else 
    set(handles.sampledist,'String',['',input]); 
    guidata(hObject,handles); 
end 

Answer 1

只是一個新的領域sampledistPrev添加到您的手柄結構。

在GUI的openingFcn，定義與這樣的行屬性：

handles.sampledistPrev = 10; %# or whatever you choose as default value 
%# if you want, you can set the default value to the GUI, so that you only need 
%# to change it at one point, if necessary, like so: 
set(handles.sampledist,'String',num2str(handles.sampledistPrev)); 
%# don't forget to save the handles structure at the end of the openingFcn 
guidata(hObject,handles) 

然後更新您的回調是這樣的：

function sampledist_Callback(hObject, eventdata, handles) 
% hObject handle to sampledist (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 sampledist as text 
%  str2double(get(hObject,'String')) returns contents of sampledist as a double 

input = str2double(get(hObject,'String')); 
if(input < 0 || input > 500) 
    errordlg('Sampled Dist. must be > 0 and < 500','Sample Dist - Input Error'); 
    set(handles.sampledist,'String',num2str(handles.sampledistPrev)); %reset value be the previous entry! 
    guidata(hObject,handles); %# Note that you don't need to save the handles structure unless 
           %# you have changed a user-defined value like sampledistPrev 
           %# It may still be useful to do it so you always remember 
else 
    set(handles.sampledist,'String',['',input]); 
    %# also update the reset value 
    handles.sampledistPrev = input; 
    guidata(hObject,handles); 
end 

Answer 2

你爲什麼不保存「的先前值「作爲該對象的'用戶數據'，如下：

---

function sampledist_Callback(hObject, eventdata, handles) 
    input = str2double(get(hObject,'String')); 
    if (input < 0 || input > 500) 
     errordlg('Sampled Dist. must be > 0 and < 500','Sample Dist - Input Error'); 
     val=get(hObject,'UserData'); 
     if isempty(val) 
      val=''; 
     end 
     set(hObject,'String',val); %<--- This is where you'd like to set the previous entry value! 
     guidata(hObject,handles); 
    else 
     input=num2str(input); 
     set(handles.sampledist,'String',input,'UserData',input); 
     guidata(hObject,handles); 
    end 
end 

---

％Y.T.