Matlab指南：从列表框中添加/删除项目

Question

我正在尝试创建一个列表框，我可以动态添加或删除项目 设置如下：

不幸的是 - 从图片中可以看出 - 当我删除元素时，列表的总长度保持不变，而不是缩小列表，显示的列表现在包含空洞。

有谁知道如何避免这种行为？

到目前为止，这是我删除按钮的代码：

function btnDeleteLabel_Callback(hObject, eventdata, handles)
    selectedId = get(handles.listbox_labels, 'Value');        % get id of selectedLabelName
    existingItems = get(handles.listbox_labels, 'String');    % get current listbox list
    existingItems{selectedId} = [];                   % delete the id
    set(handles.listbox_labels, 'String', existingItems);     % restore cropped version of label list

Answer 1

删除＆＃34;空＆＃34;的最简单方法entries将使用remainingig项更新listbox字符串。

有三种可能性：

• 第一个元素已被删除：新列表将为upd_list={existingItems{2:end}}
• 最后一个元素已被删除：新列表将为upd_list={existingItems{1:end-1}}
• ans中间元素已被删除：新列表将为upd_list={existingItems{1:selectedId-1} existingItems{selectedId+1:end}}

您还可以检查列表中的所有元素是否已被删除，在这种情况下，请禁用＆＃34;删除＆＃34; pushbutton;在这种情况下，您必须在＆＃34;添加＆＃34; callback。

btnDeleteLabel_Callback的可能实施方式可能是：

% --- Executes on button press in btnDeleteLabel.
function btnDeleteLabel_Callback(hObject, eventdata, handles)
% hObject    handle to btnDeleteLabel (see GCBO)
% eventdata  reserved - to be defined in a future version of MATLAB
% handles    structure with handles and user data (see GUIDATA)

selectedId = get(handles.listbox_labels, 'Value')        % get id of selectedLabelName
existingItems = get(handles.listbox_labels, 'String')    % get current listbox list
%
% It is not necessary
%
% existingItems{selectedId} = []                   % delete the id

% Identify the items: if in the list only one ites has been added the
% returned list is a char array
if(class(existingItems) == 'char')
   upd_list=''
   set(handles.listbox_labels, 'String', upd_list)
else
   % If the returned list is a cell array there are three cases
   n_items=length(existingItems)
   if(selectedId == 1)
      % The first element has been selected
      upd_list={existingItems{2:end}}
   elseif(selectedId == n_items)
      % The last element has been selected
      upd_list={existingItems{1:end-1}}
      % Set the "Value" property to the previous element
      set(handles.listbox_labels, 'Value', selectedId-1)
   else
      % And element in the list has been selected
      upd_list={existingItems{1:selectedId-1} existingItems{selectedId+1:end}}
   end
end
% Update the list
set(handles.listbox_labels, 'String', upd_list)     % restore cropped version of label list

% Disable the delete pushbutton if there are no more items
existingItems = get(handles.listbox_labels, 'String')
if(isempty(existingItems))
   handles.btnDeleteLabel.Enable='off'
end

希望这有帮助，

Qapla＆＃39;

Answer 2

只需用正常括号替换单元格括号：

%existingItems{selectedId} = []; % replace this with next line
existingItems(selectedId) = [];