Class Field

An interactive form (sometimes referred to as an AcroForm) is a collection of fields for gathering information interactively from the user. A PDF document may contain any number of Fields appearing on any combination of pages, all of which make up a single, global interactive form spanning the entire document.

PDFNet fully supports reading, writing, and editing PDF forms and provides many utility methods so that work with forms is simple and efficient. Using PDFNet forms API arbitrary subsets of form fields can be imported or exported from the document, new forms can be created from scratch, and the appearance of existing forms can be modified.

In PDFNet Fields are accessed through FieldIterator-s. For a full sample, please refer to 'InteractiveForms' sample project. The list of all Fields present in the document can be traversed as follows:

  
for(FieldIterator itr = doc.getFieldIterator(); itr.hasNext();) {
Field current=(Field)(itr.next());
System.out.println("Field name: " + current.getName());
System.out.println("Field partial name: " + current.getPartialName());
}

To search field by name use GetFieldIterator method. For example:

// Search for a specific field
FieldIterator itr = doc.GetFieldIterator("employee.name.first");
if (itr.hasNext()) System.out.println("Field search for " + ((Field)(itr.next())).getName() + " was successful");
else System.out.println("Field search failed");

If a given field name was not found or if the end of the field list was reached the iterator HasNext() will return false. If you have a valid iterator you can access the Field using Current() method. For example:

Field field = itr.Current();

Using Flatten(...) method it is possible to merge field appearances with the page content. Form 'flattening' refers to the operation that changes active form fields into a static area that is
part of the PDF document, just like the other text and images in the document. A completely flattened PDF form does not have any widget annotations or interactive fields.

Inheritance

System.Object

Field

Namespace: pdftron.PDF

Assembly: PDFNetAndroid.dll

Syntax

public class Field : IDisposable

Constructors

Field(Obj)

Construct a Field from a SDF dictionary representing a terminal field node.

Declaration

public Field(Obj field_dict)

Parameters

Type	Name	Description
Obj	field_dict	the field_dict

Exceptions

Type	Condition
PDFNetException	PDFNetException the PDFNet exception

Methods

Destroy()

Declaration

public void Destroy()

Dispose()

Declaration

public void Dispose()

Dispose(Boolean)

Declaration

protected virtual void Dispose(bool disposing)

Parameters

Type	Name	Description
System.Boolean	disposing

EraseAppearance()

Removes any appearances associated with the field.

Declaration

public void EraseAppearance()

Exceptions

Type	Condition
PDFNetException	PDFNetException the PDFNet exception

Finalize()

Releases all resources used by the Field

Declaration

protected void Finalize()

FindInheritedAttribute(String)

Some of the Field attributes are designated as inheritable. If such an attribute is omitted from a Field object, its value is inherited from an ancestor node in the Field tree. If the attribute is a required one, a value must be supplied in an ancestor node; if it is optional and no inherited value is specified, the default value should be used.

The function walks up the Field inhritance tree in search for specified attribute.

Declaration

public Obj FindInheritedAttribute(string attrib)

Parameters

Type	Name	Description
System.String	attrib	the attrib

Returns

Type	Description
Obj	The attribute value if the given attribute name was found or a NULL object if the given attribute name was not found. Resources dictionary (Required; inheritable) MediaBox rectangle (Required; inheritable) CropBox rectangle (Optional; inheritable) Rotate integer (Optional; inheritable)

Exceptions

Type	Condition
PDFNetException	PDFNetException the PDFNet exception

Flatten(Page)

Flatten/Merge existing form field appearances with the page content and remove widget annotation.

Form 'flattening' refers to the operation that changes active form fields into a static area that is part of the PDF document, just like the other text and images in the document. A completely flattened PDF form does not have any widget annotations or interactive fields.

Declaration

public void Flatten(Page page)

Parameters

Type	Name	Description
Page	page	the page

Remarks

an alternative approach to set the field as read only is using Field.SetFlag(Field::e_read_only, true) method. Unlike Field.SetFlag(...), the result of Flatten() operation can not be programatically reversed.

Exceptions

Type	Condition
PDFNetException	PDFNetException the PDFNet exception

GetDefaultAppearance()

Gets the default graphics state.

Declaration

public GState GetDefaultAppearance()

Returns

Type	Description
GState	The default graphics state that should be used in formatting the text. The state corresponds to /DA entry in the field dictionary.

Exceptions

Type	Condition
PDFNetException	PDFNetException the PDFNet exception

GetDefaultValue()

Gets the default value.

Declaration

public Obj GetDefaultValue()

Returns

Type	Description
Obj	The default value to which the field reverts when a reset-form action is executed or NULL if the default value is not specified. The format of field's value varies depending on the field type.

Exceptions

Type	Condition
PDFNetException	PDFNetException the PDFNet exception

GetDefaultValueAsString()

Gets the default value as string.

Declaration

public string GetDefaultValueAsString()

Returns

Type	Description
System.String	the default value as string

Exceptions

Type	Condition
PDFNetException	PDFNetException the PDFNet exception

GetFlag(Field.Flag)

Gets the flag.

Declaration

public bool GetFlag(Field.Flag flag)

Parameters

Type	Name	Description
Field.Flag	flag	the flag

Returns

Type	Description
System.Boolean	the value of given field flag

Exceptions

Type	Condition
PDFNetException	PDFNetException the PDFNet exception

GetJustification()

Gets the justification.

Declaration

public Field.TextJustification GetJustification()

Returns

Type	Description
Field.TextJustification	the form of quadding (justification) to be used in displaying the text fields.

Exceptions

Type	Condition
PDFNetException	PDFNetException the PDFNet exception

GetMaxLen()

Gets the maximum length.

Declaration

public int GetMaxLen()

Returns

Type	Description
System.Int32	The maximum length of the field's text, in characters, or a negative number if the length is not limited.

Remarks

This method is specific to a text field.

Exceptions

Type	Condition
PDFNetException	PDFNetException the PDFNet exception

GetName()

Gets the name.

Declaration

public string GetName()

Returns

Type	Description
System.String	a string representing the fully qualified name of the field (e.g. "employee.name.first").

Exceptions

Type	Condition
PDFNetException	PDFNetException the PDFNet exception

GetOpt(Int32)

Declaration

public string GetOpt(int index)

Parameters

Type	Name	Description
System.Int32	index

Returns

Type	Description
System.String

GetOptCount()

Declaration

public int GetOptCount()

Returns

Type	Description
System.Int32

GetPartialName()

Gets the partial name.

Declaration

public string GetPartialName()

Returns

Type	Description
System.String	a string representing the partial name of the field (e.g. "first" when "employee.name.first" is fully qualified name).

Exceptions

Type	Condition
PDFNetException	PDFNetException the PDFNet exception

GetSDFObj()

Gets the SDFObj.

Declaration

public Obj GetSDFObj()

Returns

Type	Description
Obj	the underlying SDF/Cos object.

Exceptions

Type	Condition
PDFNetException	PDFNetException the PDFNet exception

GetTriggerAction(Field.EventType)

Get the Action associated with the selected Field Trigger event

Declaration

public Obj GetTriggerAction(Field.EventType trigger)

Parameters

Type	Name	Description
Field.EventType	trigger	the type of trigger event to get

Returns

Type	Description
Obj	The action Obj if present, otherwise NULL

GetType()

Gets the type.

Declaration

public Field.Type GetType()

Returns

Type	Description
Field.Type	The field's value, whose type/format varies depending on the field type. See the descriptions of individual field types for further information.

Exceptions

Type	Condition
PDFNetException	PDFNetException the PDFNet exception

GetUpdateRect()

Return the rectangle that should be refreshed after changing a field.

Declaration

public Rect GetUpdateRect()

Returns

Type	Description
Rect

GetValue()

Gets the value.

Declaration

public Obj GetValue()

Returns

Type	Description
Obj	the value of the Field (the value of its /V key) or NULL if the value is not specified. The format of field's value varies depending on the field type.

Exceptions

Type	Condition
PDFNetException	PDFNetException the PDFNet exception

GetValueAsBool()

Gets the value as bool.

Declaration

public bool GetValueAsBool()

Returns

Type	Description
System.Boolean	the value as bool

Exceptions

Type	Condition
PDFNetException	PDFNetException the PDFNet exception

GetValueAsString()

Gets the value as string.

Declaration

public string GetValueAsString()

Returns

Type	Description
System.String	the value as string

Exceptions

Type	Condition
PDFNetException	PDFNetException the PDFNet exception

IsAnnot()

Checks if is annot.

Declaration

public bool IsAnnot()

Returns

Type	Description
System.Boolean	true if this Field is a Widget Annotation Determines whether or not this Field is an Annotation.

Exceptions

Type	Condition
PDFNetException	PDFNetException the PDFNet exception

IsLockedByDigitalSignature()

Returns whether modifying this field would invalidate a digital signature in the document

Declaration

public Boolean IsLockedByDigitalSignature()

Returns

Type	Description
Boolean	whether modifying this field would invalidate a digital signature in the document

IsValid()

Checks if current field is valid.

Declaration

public bool IsValid()

Returns

Type	Description
System.Boolean	whether this is a valid (non-null) Field. If the function returns false the underlying SDF/Cos object is null and the Field object should be treated as null as well.

Exceptions

Type	Condition
PDFNetException	PDFNetException the PDFNet exception

op_Assign(Field)

Assignment operator

Declaration

public Field op_Assign(Field r)

Parameters

Type	Name	Description
Field	r	a Field object

Returns

Type	Description
Field	a Field object equals to given object

RefreshAppearance()

Regenerates the appearance stream for the Widget Annotation containing variable text. Call this method if you modified field's value and would like to update field's appearance.

Declaration

public void RefreshAppearance()

Remarks

If this field contains text, and has been added to a rotated page, the text in the field may be rotated. If RefreshAppearance is called after the field is added to a rotated page, then any text will be rotated in the opposite direction of the page rotation. If this method is called before the field is added to any rotated page, then no counter rotation will be applied. If you wish to call RefreshAppearance on a field already added to a rotated page, but you don't want the text to be rotated, you can do one of the following; temporarily un-rotate the page, or, temporarily remove the "P" object from the field.

Exceptions

Type	Condition
PDFNetException	PDFNetException the PDFNet exception

Rename(String)

Modifies the field name.

Declaration

public void Rename(string field_name)

Parameters

Type	Name	Description
System.String	field_name	a string representing the fully qualified name of the field (e.g. "employee.name.first").

Exceptions

Type	Condition
PDFNetException	PDFNetException the PDFNet exception

Set(Field)

Sets to given Field object

Declaration

public void Set(Field p)

Parameters

Type	Name	Description
Field	p	a Field object

SetFlag(Field.Flag, Boolean)

Set the value of given FieldFlag.

Declaration

public void SetFlag(Field.Flag flag, bool value)

Parameters

Type	Name	Description
Field.Flag	flag	the flag
System.Boolean	value	the value

Remarks

You can use this method to set the field as read-only. An alternative approach to set the field as read only is using Page.Flatten(...) method. Unlike Flatten(...), the result of SetFlag(...) can be programatically reversed.

Exceptions

Type	Condition
PDFNetException	PDFNetException the PDFNet exception

SetJustification(Field.TextJustification)

Sets the justification to be used in displaying the text field.

Declaration

public void SetJustification(Field.TextJustification j)

Parameters

Type	Name	Description
Field.TextJustification	j	the new justification

Exceptions

Type	Condition
PDFNetException	PDFNetException the PDFNet exception

SetMaxLen(Int32)

Sets the maximum length of the field's text, in characters.

Declaration

public void SetMaxLen(int max_len)

Parameters

Type	Name	Description
System.Int32	max_len	the new maximum length

Remarks

This method is specific to a text field.

Exceptions

Type	Condition
PDFNetException	PDFNetException the PDFNet exception

SetValue(Obj)

Sets the value of the Field (i.e. the value of the field's /V key). The format of field's value varies depending on the field type.

Declaration

public ViewChangeCollection SetValue(Obj value)

Parameters

Type	Name	Description
Obj	value	the new value

Returns

Type	Description
ViewChangeCollection

Remarks

in order to remove/erase the existing value use pass a SDF::Null object to SetValue().
In PDF, Field's value is separate from its annotation (i.e. how the field appears on the page). After you modify Field's value you need to refresh Field's appearance using RefreshAppearance() method.

Alternatively, you can delete "AP" entry from the Widget annotation and set "NeedAppearances" flag in AcroForm dictionary (i.e. doc.GetAcroForm().Put("NeedAppearances", Obj.CreateBool(true)); ) This will force viewer application to auto-generate new field appearances every time the document is opened.

Yet another option is to generate a custom annotation appearance using ElementBuilder and ElementWriter and then set the "AP" entry in the widget dictionary to the new appearance stream. This functionality is useful in applications that need advanced control over how the form fields are rendered.

Exceptions

Type	Condition
PDFNetException	PDFNetException the PDFNet exception

SetValue(Boolean)

Sets the value.

Declaration

public ViewChangeCollection SetValue(bool is_checked)

Parameters

Type	Name	Description
System.Boolean	is_checked	the new value

Returns

Type	Description
ViewChangeCollection

Exceptions

Type	Condition
PDFNetException	PDFNetException the PDFNet exception

SetValue(String)

Sets the value.

Declaration

public ViewChangeCollection SetValue(string value)

Parameters

Type	Name	Description
System.String	value	the new value

Returns

Type	Description
ViewChangeCollection

Exceptions

Type	Condition
PDFNetException	PDFNetException the PDFNet exception

UseSignatureHandler(SignatureHandlerId)

Sets the signature handler to use for adding a signature to this field. If the signature handler is not found in PDFDoc's signature handlers list, this field will not be signed. To add signature handlers, use PDFDoc.AddSignatureHandler method. If a signature handler is already assigned to this field and this method is called once again, the associate signature handler for this field will be updated with the new handler.

Declaration

public Obj UseSignatureHandler(SignatureHandlerId signature_handler_id)

Parameters

Type	Name	Description
SignatureHandlerId	signature_handler_id	The unique id of the SignatureHandler to use for adding signature in this field.

Returns

Type	Description
Obj	The signature dictionary created using the SignatureHandler, or null if the signature handler is not found.