Java Reference
In-Depth Information
Creating Styled Text
In Chapter 15, you looked at displaying plain text and HTML. With the Swing text components—
or at least the
JTextPane
—you can also display stylized text, in which different blocks of text
can have multiple attributes. These attributes might include boldface, italics, a different font
or color at the character level, or justification at the paragraph level, just as with any of the
modern word processors.
To support these capabilities, Swing supplies many different interfaces and classes, all of
which start with the specialized
Document
interface extension of
StyledDocument
. The
Document
interface was introduced in Chapter 15, focusing on the
PlainDocument
implementation class.
The
StyledDocument
interface, or more precisely, the
DefaultStyledDocument
implementation,
manages a series of styles and attribute sets for the contents of a
Document
.
The various styles used by a
StyledDocument
are described initially by the
AttributeSet
interface, which is a set of key/value pairs of read-only attributes. The key for an attribute
might be “current font,” in which the setting would be the font to use. To actually change the
font, you need to move on to the
MutableAttributeSet
interface, which supplies the ability to
add and remove attributes. For instance, if you had an
AttributeSet
for “bold,” you could use
MutableAttributeSet
to also add italics, underlining, or colorization (or all three) to the set.
For a simple implementation of
AttributeSet
, there is the
StyleContext.SmallAttributeSet
class, which uses an array to manage the set of attributes. For an implementation of the
MutableAttributeSet
interface, there is the
SimpleAttributeSet
class, which uses a
Hashtable
to manage the attributes. More complex attribute sets move on to the
Style
interface, which
adds a name to the set of attributes as defined by a
MutableAttributeSet
. The actual
Style
implementation class is the
StyleContext.NamedStyle
class. Besides adding a name, the
Style
interface adds the ability to have a
ChangeListener
monitor a set of attributes for changes.
The class that manages the set of
Style
objects for a
StyledDocument
is the
StyleContext
class. An implementation of the
AbstractDocument.AttributeContext
interface,
StyleContext
uses the
StyleConstants
class, which defines various attributes for commonly used styles.
When working with HTML documents, the
StyleContext
is actually a
StyleSheet
, which may
help you in understanding the whole arrangement. Keep in mind that all of the classes and
interfaces discussed here (except
StyleSheet
) are required just to set up the
Document
data
model for a particular
JTextPane
.
StyledDocument Interface and DefaultStyledDocument Class
The
StyledDocument
interface extends the
Document
interface by adding the ability to store
styles for the content of the document. These styles can describe the character or paragraph
attributes, such as color, orientation, or font.
public interface StyledDocument extends Document {
public Style addStyle(String nm, Style parent);
public Color getBackground(AttributeSet attribute);
public Element getCharacterElement(int position);
public Font getFont(AttributeSet attribute);
public Color getForeground(AttributeSet attribute);
