MATLAB: Difference between properties and handles of figure

figureguihandlesproperty

I'm trying to understand the difference between the handles of a figure and the property values of a figure.

for example I can use

h=figure

then I can get the properties of h by using inspect. Also I can get the handles by using handles=guihandles(h).

What is the difference between those values and are the property values of the figure actually somewhere in the handles too?

Another thing, if I use handles=guihandles(h) and then handles.FigureToolBar.Visible='off' my figure is directly updated. So why do I need to call guidata(h,handles) as I have seen in some documentations?

Thanks a lot for helping

Best Answer

The figure command replies the "handle" of the figure, which is a kind of pointer to it. You can use it to identify the figure uniquely and access its properties.

The command guihandles creates a struct, which makes it easy to access the propertioes of the figure (or other GUI object).

guidata writes or reads a struct from the figure's ApplicationData, which is useful to share data between callbacks of a figure. The usual name "handles" for this struct is confusing, because it can contain anything and not only handles. "guidata" would be a much better name, but unfortunately this is used for the command already.

Related Solutions

MATLAB: GUIDATA does not trasfer data in GUIDE with subfunctions.

Alborz - your code has interesting approach by assigning the ButtonDownFcn to the line object so that when the user presses down on the line (and only the line), this event will fire. Though instead of calling guidata with hObject which is the handle to the line object, you probably want to call it with the handle to the button, h, since it is a child of the GUI and the handles structure is "associated" with that. So the pushbutton_vertline_Callback code would change to

 function pushbutton_vertline_Callback_Callback(hButton, eventdata,handles)
    axis_h = handles.axis_h;
    vertline_h = line('parent',axis_h,'xdata',[1 1],'ydata',[-1 1], 'ButtonDownFcn', @mouseDown );
    handles.vertline_h = vertline_h;
    guidata(h,handles)
    % MouseMove subfunction in callback 2

    function mouseDown(hObject,event)
        mousedown = true;
        handles.mousedown = mousedown;
        guidata(hButton,handles)
    end
 end

Like Walter has indicated, your mousedown variable is local to the MouseUp function and so setting it to true won't affect the field within the handles structure. So this function should change to

 function MouseUp(h,event) %#ok<*INUSD>

    handles = guidata(hObject);
    handles.mousedown = false;
    guidata(hObject,handles);
 end

Note how in the above code, we use hObject (the handle to the pushbutton_plot) to get the latest updated version of handles rather than the older copy from the pushbutton_plot_Callback callback. So we get the latest version, change the mousedown field, and then save the updated handles structure.

And the MouseMove is almost correct with the only problem being that the handles of copy being used rather than the latest version. Again, we just need to call guidata as

 function MouseMove(h,event)
     handles = guidata(hObject);
     if isfield(handles,'mousedown')
         mousedown = handles.mousedown;
     else
         mousedown = false;
     end
     if mousedown
         cp = get ( axis_h, 'CurrentPoint' );
         vertline_h = handles.vertline_h;
         set ( vertline_h, 'XData', [cp(1,1) cp(1,1)] );
     end
 end

See below for the full code which should work.

 % Callbacl 1: Graph SIN function 
 function pushbutton_plot_Callback(hObject, eventdata, handles)   
    clc;
    open_figs_h = get(0,'children');
    close(open_figs_h(2:end));
    x = -pi:0.01:pi;
    y = sin(x);
    fig_h = figure('units','normalized','outerposition',[0.2 0.2 .5 .5],...
                   'WindowButtonMotionFcn', @MouseMove, 'WindowButtonUpFcn', @MouseUp );
    axis_h = axes('parent',fig_h,'position',[0.1 0.1 .8 .8]);
    line('parent',axis_h,'xdata',x,'ydata',y);
    handles.axis_h = axis_h;
    guidata(hObject,handles);
    % MouseUp and MouseMove subfunctions in callback 1
    function MouseUp(h,event) %#ok<*INUSD>
        handles = guidata(hObject);
        handles.mousedown = false;
        guidata(hObject,handles);
    end
    function MouseMove(h,event)
        handles = guidata(hObject);
        if isfield(handles,'mousedown')
            mousedown = handles.mousedown;
        else
            mousedown = false;
        end
        if mousedown
            cp = get ( axis_h, 'CurrentPoint' );
            vertline_h = handles.vertline_h;
            set ( vertline_h, 'XData', [cp(1,1) cp(1,1)] );
        end
    end
 end 
 % Callbacl 2: Graph movables vertical line      
 function pushbutton_vertline_Callback(hButton, eventdata,handles)
    axis_h = handles.axis_h;
    vertline_h = line('parent',axis_h,'xdata',[1 1],'ydata',[-1 1], 'ButtonDownFcn', @mouseDown );
    handles.vertline_h = vertline_h;
    guidata(h,handles)
    % MouseMove subfunction in callback 2
    function mouseDown(hObject,event)
        mousedown = true;
        handles.mousedown = mousedown;
        guidata(hButton,handles)
    end
  end

MATLAB: Problems in saving GUI’s handles structure

The function guihandles creates a struct using the tags of the graphic objects as fieldnames and the handles of the objects as values. But the guidata function stores a struct in the figure's ApplicationData. Therefore the replies of these two functions are not directly related.

Try this instead to find the hfreq field:

data = guidata(gcf)

It increases the confusion level, that TMW decided to call the struct for storing GUI related data "handles" also as default.

Best Answer

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MATLAB: GUIDATA does not trasfer data in GUIDE with subfunctions.

MATLAB: Problems in saving GUI’s handles structure

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