MATLAB: Does findobj not work with annotation tags

annotation;findobjtag

When I create an annotation with a Tag and use findobj the result is empty.

an = annotation('textbox',[0 0 1 1],'string','Hallo','Tag','annotation');
findobj('Tag','annotation')

Best Answer

findall returns the hg-handle. However, I find it strange that findobj fails, since HandleVisibility is on (by default). Matlab seems to behave this way and documentation is hard to read.

    >> an = annotation('textbox',[0 0 1 1],'string','Hello','Tag','annotation');
    >> h1 = findobj('Tag','annotation')
    h1 =
       Empty matrix: 0-by-1
    >> h2 = findall(0,'Tag','annotation')
    h2 =
      178.0016
    >> get( h2, 'HandleVis' )
    ans =
    on
    >>

With R2012a,64bit,Win7

@Walter

Yes, an and h2 seems to be the same

    ....
    >> [an,h2]
    ans =
      178.0024  178.0024
    >> get( [an,h2], 'type' )
    ans = 
        'hggroup'
        'hggroup'
    >> get( [an,h2], 'tag' )
    ans = 
        'annotation'
        'annotation'
     >>

However, you spotted the cause

    >> axh = get( h2, 'parent' )
    axh =
      173.0024
    >> get( axh, 'HandleVis' )
    ans =
    off

annotation returns the handle of a hggroup, which is the child of an axes the HandleVisibility of which is off.

Related Solutions

MATLAB: Findobj cannot find a TexBox (annotation) object

Try using the object handle (txb) directly.

plot(1:10)
str = 'Straight Line Plot from 1 to 10';
txb = annotation('textbox',[.2 .5 .3 .3],'String',str,'FitBoxToText','on');
●
% Use object handle
findobj(txb)
ans = 
  TextBox (Straight Line Plot from 1 to 10) with properties:

             String: 'Straight Line Plot from 1 to 10'
           FontName: 'Helvetica'
           FontSize: 10
         FontWeight: 'normal'
              Color: [0 0 0]
    BackgroundColor: 'none'
          EdgeColor: [0 0 0]
          LineStyle: '-'
          LineWidth: 0.5000
           Position: [0.2000 0.5000 0.3000 0.3000]
              Units: 'normalized'

  Show all properties

If you want to instead find the annotation without using the object handle, use findall instead.

findall(gcf,'Type','textboxshape')
ans = 
  TextBox (Straight Line Plot from 1 to 10) with properties:

             String: 'Straight Line Plot from 1 to 10'
           FontName: 'Helvetica'
           FontSize: 10
         FontWeight: 'normal'
              Color: [0 0 0]
    BackgroundColor: 'none'
          EdgeColor: [0 0 0]
          LineStyle: '-'
          LineWidth: 0.5000
           Position: [0.2000 0.5000 0.3000 0.3000]
              Units: 'normalized'

  Show all properties

MATLAB: How to get the properties of annotation objects in the current figure

To obtain the properties and values of annotation objects in the current figure, search the figure using the FINDALL function to locate hggroup objects that are children of the annotation object parent axes. The following code provides an example:

close all
clear all
% Create some annotations
annotation('textbox',[0.5 0.5 0.1 0.1],'string','hello world');
annotation('textbox',[0.7 0.9 0.1 0.1],'string','hello world1');
annotation('textbox',[0.2 0.2 0.1 0.1],'string','hello world2');
annotation('line',[0.2 0.2],[0.8 0.3]);
fig = gcf;
% Return the axes that contains the annotation objects
ax = findall(fig, 'Type', 'axes', 'Tag', 'scribeOverlay');
% Find the Children with type hggroup
annotation_handles = findall(get(ax,'Children'),'Type','hggroup');
ss = size(annotation_handles);
j = max(ss);
% In a loop, determine if the annotations are of textbox type
for i = 1:j
     hh = get(annotation_handles(i));
     % Check if the object has a 'String' property
     if(isfield(hh,'String'))
     text_string{i} = get(annotation_handles(i),'string');
     else i = i+1;
     end
end
% Display the strings in the annotation textboxes
text_string

It is important to note that all annotation objects are of type 'hggroup' and hence based on the type you cannot determine whether it is a textbox or a line. Hence, you will need to find if the 'String' property exists in the handle structure of the annotation object.

Best Answer

Related Solutions

MATLAB: Findobj cannot find a TexBox (annotation) object

MATLAB: How to get the properties of annotation objects in the current figure

Related Question