Why won't my GUI code work!?

4 次查看（过去 30 天）
Grant Dickson
Grant Dickson 2012-11-21
I have built a GUI using GUIDE. I have a lot of handles so have only included the code of the call back functions for one of each handle type here: c_callback (edit text box), c_slider_callback(slider), c_unit_callback(drop down menu), and calculate.callback(push button):
-------------------------------------------------------------------------------
function c_Callback(hObject, eventdata, handles)
% Obtain the new c value entered in the box
NewVal = str2double(get(hObject,'String'));
% If there is no value or it is outwith limits, restore to the previous value from the slider
if isempty(NewVal) || (NewVal<get(handles.c_slider,'Min')) || (NewVal>get(handles.c_slider,'Max'))
set(hObject,'String',get(handles.c_slider,'Value'));
% Otherwise the value is correct so change the slider value
else
set(handles.c_slider,'Value',NewVal)
end
-------------------------------------------------------------------------------
% --- Executes on button press in calculate.
function Calculate_Callback(hObject, eventdata, handles)
c_unit_Callback(hObject, eventdata, handles)
h_0_unit_Callback(hObject, eventdata, handles)
omega_unit_Callback(hObject, eventdata, handles)
r_0_unit_Callback(hObject, eventdata, handles)
F_unit_Callback(hObject, eventdata, handles)
n_p = (get(handles.n_p_slider, 'value'));
c = (get(handles.c_slider, 'value'))*c_unit;
nu = (get(handles.nu_slider, 'value'));
h_0 = (get(handles.h_0_slider, 'value'))*h_0_unit;
omega = (get(handles.omega_slider,'value'))*omega_unit;
r_0 = (get(handles.r_0_slider, 'value'))*r_0_unit;
F = (get(handles.F_slider, 'value'))*F_unit;
n = (get(handles.n_slider, 'value'));
% THIS IS JUST CODE FOR CALCULATIONS. NOT IMPORTANT:
theta = (0.8*360/n_p)*pi/180;
r = r_0;
F_max = 0;
while F_max < F;
r = r + 10E-3; % increase radius by 1 mm
U = r*omega; % calculate tangential velocity U at radius r
L = r*theta; % calculate arc length L at radius r
x = linspace(0,L,n+1);
delta_x = L/n;
h = h_0 + x*tan(c);
p = zeros(1,n+1);
p_max_old = 0; p_max_new = 1;
while abs(p_max_new-p_max_old)>(0.001E-2*p_max_new)
p_max_old=p_max_new;
for i=2:n
p(1,(i)) = (p(1,(i+1)) + p(1,(i-1)))/2 ...
+ (3*c*(p(1,(i+1)) - p(1,(i-1))) * delta_x)./(4*h(1,i))...
+ (3*nu*U*c*delta_x^2)./h(1,i).^3;
end
p_max_new=max(p);
end
p_mean = mean(p);
A = pi*(r^2-r_0^2)*theta/(2*pi); % find area of pad
F = p_mean*A; % find maximum force
end
% END OF CALCULATIONS. IMPORTANT:
% display the results in the text boxes
set(handles.P_max,'string',num2str(p_max_new));
set(handles.A,'string',num2str(A));
set(handles.D,'string',num2str(2*r));
-------------------------------------------------------------------------------
% --- Executes on selection change in c_unit.
function c_unit_Callback(hObject, eventdata, handles)
% retrieve unit selection from drop down list
str = get(hObject, 'String'); % Obtain the pop up selection string
val = get(hObject, 'Value'); % Obtain the pop up selection value
switch str{val};
case 'mrad' % If the choice is mrad set c_unit to 1E-3
c_unit=1E-3;
case 'rad' % If the choice is rad set c_unit to 1
c_unit=1;
case 'deg' % If the choice is rad set c_unit to pi/180
c_unit=pi/180;
end
-------------------------------------------------------------------------------
% --- Executes on slider movement.
function c_slider_Callback(hObject, eventdata, handles)
% Put the current slider value in the corresponding text box
set(handles.c,'String',num2str(get(hObject,'Value')));
-------------------------------------------------------------------------------
When I run the code the GUI appears. When I click the calculate button the following error appears:
-------------------------------------------------------------------------------
??? Cell contents reference from a non-cell array object.
Error in ==> GUI>c_unit_Callback at 454
switch str{val};
Error in ==> GUI>Calculate_Callback at 305
c_unit_Callback(hObject, eventdata, handles)
Error in ==> gui_mainfcn at 96
feval(varargin{:});
Error in ==> GUI at 42
gui_mainfcn(gui_State, varargin{:});
Error in ==> @(hObject,eventdata)GUI('Calculate_Callback',hObject,eventdata,guidata(hObject))
??? Error while evaluating uicontrol Callback
-------------------------------------------------------------------------------
Line 454 is: switch str{val};
Any help is much appreciated. Thanks

请先登录，再回答此问题。

回答（3 个）

Matt Fig
Matt Fig 2012-11-21
What is in the popup menu? To see this, take the semicolon off of the line where you retrieve the string, like this:
str = get(hObject, 'String')% Obtain the pop up selection string
Then when you run the GUI and select something from that popup, show us what prints out to the screen.
  1 个评论
Matt Fig
Matt Fig 2012-11-22
Grand comments:
Thanks for the reply. I defined the popup menu with the string field in the property editor of GUIDE. Following your instructions, the command window shows str =
'mrad'
'rad'
'deg'
Hopefully this helps you work out my problem

请先登录，再进行评论。

Jan
Jan 2012-11-21
编辑：Jan 2012-11-21
Please set a breakpoint in the line 454 "switch str{val}". Then run the program until it stops there. Now check the type and size of "str".
Another method to debug is:
dbstop if error
Then the program stops, if the error occurs. Then the variable "str" can be checked again. I guess, that the callback function is called from another function also, which replies a string instead of a cell string.
  1 个评论
Matt Fig
Matt Fig 2012-11-22
Grant comments
Okay,
setting the breakpoint and running the program to there, str is: >> str ??? Undefined function or variable 'str'.
Then typing dbstop if error into the command window and checking str:
K>> str
str =
Calculate
str shouldn't be Calculate, it should be: 'mrad' 'rad' 'deg'
Any idea where the problem lies? I'll search for it in the meantime

请先登录，再进行评论。

Nick
Nick 2013-1-25
by using:
str = get(hObject, 'String');
You call the name/ tag of the popupmenu and not the string that is inside the popupmenu. From the comment you gave on Jan Simon I gess the Tag you assigned to your popupmenu is Calculate. If this is true I would surgest the following code:
handles = guidata(gcbo);
str = get(handles.Calculate, 'String');
%str now contains all strings from the popupmenu
val = get(handles.Calculate,'Value');
%the value now is the selected value from the popupmenu
switch str(val)
%etc

类别

在 Help Center 和 File Exchange 中查找有关 Migrate GUIDE Apps 的更多信息

标签

Community Treasure Hunt

Find the treasures in MATLAB Central and discover how the community can help you!

Start Hunting!

Translated by