How to interrupt an executing while loop in GUI by clicking another 'EXIT' button without error for calling deleted Objects

Hi, Can anyone help me solve this problem? I don't quite know the process of interrupting a while loop by clicking another button in a unpredictable time. My design is:

I designed two push button： Control button, with a while loop, to start/stop plot something dynamically on several AXES objects; EXIT button to exit the interface and clear everything. My problem is if I want to exit without any error, I need to first click the Control button to stop the dynamical plotting, then I could click EXIT button. If I click the EXIT button while the plotting is going, I will get error message for executing the while loop.

Followed is the button callback part and the error messages? ***************************************************

 function Control_Callback(hObject, eventdata, handles)

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

 handles.str = get(handles.Control,'String');
 guidata(hObject, handles);
 set(handles.Exit,'string','EXIT')
  if strcmp(handles.str,'Stop')
        set(handles.Control,'String','Resume plotting')
  else
    set(handles.Control,'String','Stop')
  end

 while (strcmp(get(handles.Control,'String'),'Stop'))

    handles.gx =-1 + 2*rand(1);
    handles.gy =-1 + 2*rand(1);
    handles.gz =-1 + 2*rand(1);
    handles.magnitude = (handles.gx^2+handles.gy^2+handles.gz^2)^0.5;

    handles.magdata = [handles.magdata(2:end);handles.magnitude];
    handles.gxdata = [handles.gxdata(2:end);handles.gx];
    handles.gydata = [handles.gydata(2:end);handles.gy];
    handles.gzdata = [handles.gzdata(2:end);handles.gz];

    guidata(hObject,handles); % use this to save all those previous data to relize the function of "Pause"

    axes(handles.axes1);
    cla;
    line([0 handles.gx], [0 0],[0 0], 'Color', 'r', 'LineWidth', 2, 'Marker', 'o');
    line([0 0], [0 handles.gy],[0 0], 'Color', 'g', 'LineWidth', 2, 'Marker', 'o');
    line([0 0], [0 0],[0 handles.gz], 'Color', 'b', 'LineWidth', 2, 'Marker', 'o');
    line([0 handles.gx], [0 handles.gy],[0 handles.gz], 'Color','k', 'LineWidth', 2, 'Marker', 'o');

        %limit plot to +/- 1.25 g in all directions and make axis square
    handles.limits = 2.5;
    axis([-handles.limits handles.limits -handles.limits handles.limits -handles.limits handles.limits]);
    axis square;
    grid on
    xlabel('X-axis acceleration')
    ylabel('Y-axis acceleration')
    zlabel('Z-axis acceleration')

    axes(handles.axes2);
    plot(handles.index,handles.magdata,'k');
    axis([1 handles.buf_len -3.5 3.5]);  
    xlabel('time');
    ylabel('Magnitude');

    axes(handles.axes3)
    plot(handles.index,handles.gxdata,'r', handles.index,handles.gydata,'g', handles.index,handles.gzdata,'b');
    axis([1 handles.buf_len -3.5 3.5]);  
    xlabel('time');
    ylabel('Components');

drawnow     
end

 % --- Executes on button press in Exit.

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

 % to void the while loop condition 
 set(handles.Control,'String','Resume plotting') 
 % pause to wait for finishing the last while loop 
 pause(0.05)

 clc
 clear all
 close all

Depending on the time I click EXIT button and the pause time, I can get errors to different part of the while loop.

*********************************************

Error using handle.handle/get Invalid or deleted object.

Error in untitled>Control_Callback (line 125) while (strcmp(get(handles.Control,'String'),'Stop'))

Error in gui_mainfcn (line 96) feval(varargin{:});

Error in untitled (line 48) gui_mainfcn(gui_State, varargin{:});

Error in @(hObject,eventdata)untitled('Control_Callback',hObject,eventdata,guidata(hObject))

Error while evaluating uicontrol Callback

********************************************

Error using axes Invalid object handle

Error in untitled>Control_Callback (line 164) axes(handles.axes3)

Error in gui_mainfcn (line 96) feval(varargin{:});

Error in untitled (line 48) gui_mainfcn(gui_State, varargin{:});

Error in @(hObject,eventdata)untitled('Control_Callback',hObject,eventdata,guidata(hObject))

Error while evaluating uicontrol Callback

Answer 1

[Jan]

Modify the Exit callback:

if strcmp(get(handles.Control, 'String'), 'Stop')
  % Let the loop finish at first!
  set(handles.Control, 'String', 'Wait');
  drawnow;
  return;
end
... do your cleanup here

And insert after the WHILE loop:

if strcmp(get(handles.Control,'String'), 'Wait')
  Exit_Callback(handles.Control, [], handles);
end

Now hitting the EXIT button allows to finish the WHILE loop accurately at first and trigger the EXIT callback again afterwards.

[Bin]

Thanks Jan! That's a great solution by calling Exit_Callback in the WHILE loop! I learnt from you on using return and call another button's callback function. Just one more 'return' should be added:

 if strcmp(get(handles.Control,'String'), 'Wait')
   Exit_Callback(handles.Control, [], handles);
   return
 end

I also got another similar solution to share:

****************************************

insert the following inside the while loop at the end after command 'drawnow'

 if get(handles.Control,'Userdata')%x == 12
     clc            % close if the EXIT button has been pressed
     close all
     clear all
     return % or use break
 end

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

if ~strcmp(get(handles.Control,'String'),'Stop')
   clc            % close if the plotting has been stop in advance
   close all
   clear all
else
   set(handles.Control,'Userdata',1)

 end

Answer 2

[Sean de Wolski]

You could always check: ishandle(handles.h) before trying to get()