public PDAppearance(PDAcroForm theAcroForm,
    PDVariableText field) throws IOException 
{
        acroForm = theAcroForm;
        parent = field;
        widgets = field.getKids();
        if( widgets == null )
        {
            widgets = new ArrayList();
            widgets.add( field.getWidget() );
        }
        defaultAppearance = getDefaultAppearance();
}

Constructs a COSAppearnce from the given field.

Parameters:

theAcroForm - the acro form that this field is part of.

field - the field which you wish to control the appearance of

Throws:

IOException - If there is an error creating the appearance.

 public  void setAppearanceValue(String apValue) throws IOException 
{
        // MulitLine check and set
        if ( parent.isMultiline() && apValue.indexOf('\n') != -1 )
        {
            apValue = convertToMultiLine( apValue );
        }
        value = apValue;
        Iterator widgetIter = widgets.iterator();
        while( widgetIter.hasNext() )
        {
            Object next = widgetIter.next();
            PDField field = null;
            PDAnnotationWidget widget = null;
            if( next instanceof PDField )
            {
                field = (PDField)next;
                widget = field.getWidget();
            }
            else
            {
                widget = (PDAnnotationWidget)next;
            }
            PDFormFieldAdditionalActions actions = null;
            if( field != null )
            {
                actions = field.getActions();
            }
            if( actions != null &&
                actions.getF() != null &&
                widget.getDictionary().getDictionaryObject( "AP" ) ==null)
            {
                //do nothing because the field will be formatted by acrobat
                //when it is opened.  See FreedomExpressions.pdf for an example of this.
            }
            else
            {
                PDAppearanceDictionary appearance = widget.getAppearance();
                if( appearance == null )
                {
                    appearance = new PDAppearanceDictionary();
                    widget.setAppearance( appearance );
                }
                Map normalAppearance = appearance.getNormalAppearance();
                PDAppearanceStream appearanceStream = (PDAppearanceStream)normalAppearance.get( "default" );
                if( appearanceStream == null )
                {
                    COSStream cosStream = new COSStream( acroForm.getDocument().getDocument().getScratchFile() );
                    appearanceStream = new PDAppearanceStream( cosStream );
                    appearanceStream.setBoundingBox( widget.getRectangle().createRetranslatedRectangle() );
                    appearance.setNormalAppearance( appearanceStream );
                }
                List tokens = getStreamTokens( appearanceStream );
                List daTokens = getStreamTokens( getDefaultAppearance() );
                PDFont pdFont = getFontAndUpdateResources( tokens, appearanceStream );
                if (!containsMarkedContent( tokens ))
                {
                    ByteArrayOutputStream output = new ByteArrayOutputStream();
                    //BJL 9/25/2004 Must prepend existing stream
                    //because it might have operators to draw things like
                    //rectangles and such
                    ContentStreamWriter writer = new ContentStreamWriter( output );
                    writer.writeTokens( tokens );
                    output.write( " /Tx BMC\n".getBytes() );
                    insertGeneratedAppearance( widget, output, pdFont, tokens, appearanceStream );
                    output.write( " EMC".getBytes() );
                    writeToStream( output.toByteArray(), appearanceStream );
                }
                else
                {
                    if( tokens != null )
                    {
                        if( daTokens != null )
                        {
                            int bmcIndex = tokens.indexOf( PDFOperator.getOperator( "BMC" ));
                            int emcIndex = tokens.indexOf( PDFOperator.getOperator( "EMC" ));
                            if( bmcIndex != -1 && emcIndex != -1 &&
                                emcIndex == bmcIndex+1 )
                            {
                                //if the EMC immediately follows the BMC index then should
                                //insert the daTokens inbetween the two markers.
                                tokens.addAll( emcIndex, daTokens );
                            }
                        }
                        ByteArrayOutputStream output = new ByteArrayOutputStream();
                        ContentStreamWriter writer = new ContentStreamWriter( output );
                        float fontSize = calculateFontSize( pdFont, appearanceStream.getBoundingBox(), tokens, null );
                        boolean foundString = false;
                        for( int i=0; i< tokens.size(); i++ )
                        {
                            if( tokens.get( i ) instanceof COSString )
                            {
                                foundString = true;
                                COSString drawnString =((COSString)tokens.get(i));
                                drawnString.reset();
                                drawnString.append( apValue.getBytes() );
                            }
                        }
                        int setFontIndex = tokens.indexOf( PDFOperator.getOperator( "Tf" ));
                        tokens.set( setFontIndex-1, new COSFloat( fontSize ) );
                        if( foundString )
                        {
                            writer.writeTokens( tokens );
                        }
                        else
                        {
                            int bmcIndex = tokens.indexOf( PDFOperator.getOperator( "BMC" ) );
                            int emcIndex = tokens.indexOf( PDFOperator.getOperator( "EMC" ) );
                            if( bmcIndex != -1 )
                            {
                                writer.writeTokens( tokens, 0, bmcIndex+1 );
                            }
                            else
                            {
                                writer.writeTokens( tokens );
                            }
                            output.write( "\n".getBytes() );
                            insertGeneratedAppearance( widget, output,
                                pdFont, tokens, appearanceStream );
                            if( emcIndex != -1 )
                            {
                                writer.writeTokens( tokens, emcIndex, tokens.size() );
                            }
                        }
                        writeToStream( output.toByteArray(), appearanceStream );
                    }
                    else
                    {
                        //hmm?
                    }
                }
            }
        }
}

This is the public method for setting the appearance stream.