MATLAB: Attempt to reference field of non-structure array

handlesmatlab gui

Hi, I'm trying to open a gui from other gui, by separate both works fine, but when I open the second guide and get some values that says 'Attempt to reference field of non structure array Error T1=get(handles.T,'String') ' Please help me My code

    function T..Callback(hObject,evendata,handles)
....
T1=get(handles.T,'String')

Best Answer

Each handles structure is associated with a particular figure. When you are using GUIDE, the handles structure that would be automatically referenced on your behalf would belong to the figure (GUI) that the graphics object is part of. That handles structure is not going to know anything about the handles structure of the other figure (GUI) unless you specifically passed in that information.

When the first GUI calls upon the second GUI, the figure handle of the second GUI will be returned to the caller in the first GUI. The first GUI can then use guidata() on the second figure's figure handle in order to get the second GUI's handles, and the first GUI can then write the first GUI's figure handle into the second GUI's handles. Then in the second GUI, when something is needed out of the first GUI, that recorded figure handle can be used to retrieve the first GUI's handles. For example,

%in first gui
fig1 = gcf();          %first GUI's figure handle
fig2 = SecondGUI();    %returns second GUI's figure handle
handles2 = guidata(fig2);   %fetch second GUI's handles
handles2.fig1 = fig1;       %record first GUI's figure handle
guidata(fig2, handles2);    %and update second GUI's handles

and in second GUI

function some_callback(hObject, event, handles)
  %in second GUI, handles refers to handles for second GUI
  %and we stored a copy of the first GUI's figure handle there
  fig1 = handles.fig1;
  handles1 = guidata(fig1);     %retrieve handles for first GUI
  get(handles1.T, 'String')     %reference to something in first GUI

Alternately, in the case where there is only one object with the tag T, you can skip all of this and instead use

   function some_callback(hObject, event, handles)
     T = findall(0, 'Tag', 'T');    %come out come out where-ever you are!
     get(T, 'String')

findall can search all objects in all figures. It is not as efficient as the code from above, and you have complications if there are multiple objects with the same Tag.

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MATLAB: I need help in uitable

Get the data from the table like this

data = get(handles.uitable1, 'data');

Then to get the contents of the grid at the point where row 1 and column 3 intersect, simply do this:

theValue = data(1, 3);

MATLAB: Opening Another Figure Doesn’t Create Handles in GUIDE. How to fix it

"I need these handles to be created by opening .fig file directly. How can this be achieved?"

That will never happen automatically when you use openfig('Filename.fig) or open('Filename.fig')

The handles structure is created as a side effect of the call to gui_mainfcn() . That call is at the end of the "Begin initialization code - DO NOT EDIT" section of the first function in the .m that corresponds to the .fig file -- so the handles structure is not created and stored against the figure unless the .m file is executed.

In turn, gui_mainfcn() calls guihandles() with the figure handle to create the handles structure, and then uses guidata() to store the resulting structure attached to the figure.

The handles structure is stored against a particular figure. When GUIDE creates a callback to a routine, the figure that it accesses to try to locate the handles structure is the figure to which the object being invoked belongs. For example, for the Callback for the radio button with the tag 'centrifugal_fan', GUIDE will set the Callback property of the radio button to

   @(hObject,eventdata) noise_fan2('centrifugal_fan_Callback', hObject, eventdata, guidata(hObject))

This is an anonymous function that will be invoked with the standard callback arguments of the radio button object itself, and some event-specific data, and the anonymous function calls into the .m file, passing in the object (the radio button) and the event data, and the guidata retrieved relative to the radio button object itself -- which is to say, the handles subset that is stored against the figure that the button is part of.

The handles structure used is not some kind of handles structure of a "project", or of a "GUI": it is the handles structure attached to that one figure. And that in turn means that if you use GUIDE to in any way create or open or manipulate multiple figures, each of the figures will have independent handles structure... provided that a handles structure was initialized for the figure at all. If no handles structure was initialized for the figure, then the code will crash with exactly the error you are seeing, about struct reference to a non-struct object.

Thus, if you are going to openfig() to bring in a new figure file, then you need to work it like this:

fig2 = openfig('AppropriateFigFileName.fig');
handles2 = guihandles(fig2);
guidata(fig2, handles2);

and then you can access handles on the second figure.

Notice that when you do this, that the original handles structure and the second handles structure do not know about each other. If, for example, the new figure brought in... say, a pushbutton named ChooseGearRatio, then handles.ChooseGearRatio will not work to access it. The callbacks will not be able to refer to the other figure -- not unless you specifically program them to know about each other.

For example, you could:

mainfig = gcf;    %the figure handle of the existing gui
fig2 = openfig('AppropriateFigFileName.fig');
handles.fig2 = fig2;
guidata(mainfig, handles);  %refer to the new figure in the current handles
handles2 = guihandles(fig2);
handles2.mainfig = mainfig; %refer to the original figure in handles2
guidata(fig2, handles2);

Then the old figure would be able to use

handles.fig2.ChooseGearRatio

to refer to the ChooseGearRatio object in the other figure, and the new figure would be able to use handles.mainfig.whatever to refer to what the first figure knows as handles.whatever

Best Answer

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