Styling text - An Introduction to Graphical User Interfaces with Java Swing - page 221

insertString(int offset, String text, AttributeSet attrSet) inserts
the symbols in string text before the symbol currently at position offset
in the document. The new text is formatted as specified in attrSet .If
the parameters are outside the current size of the document then a Bad-
LocationException will occur.
remove(int offset,int length) deletes as many symbols as the current value
of length , starting with the one currently at position offset .Ifthe parameters
are outside the current size of the document then a BadLocationException
will occur.

The text of a document is often read from some file. This is easily done using the
utility class EditorKit , which is also found in the javax.swing.text package.
Every Swing component textComp that can display documents has an editor kit.
It can be accessed by textComp.getEditorKit() .Weneed the following method
from EditorKit :

read(FileReader fReader,Document doc, int offset);

The file reader should be assigned to the file whose content we want to insert
into the document doc . Parameter offset specifies that position in the document
before which the file content is inserted. For a new document offset = 0 is used.
The following code snippet demonstrates the use. We want to read a file filename
into DefaultStyledDocument called doc and then display it in a Swing component
textComp :

DefaultStyledDocument doc = new DefaultStyledDocument();
textComp.setDocument(doc);
EditorKit ediKit = textComp.getEditorKit();
FileReader fReader = new FileReader(filename);
ediKit.read(fReader,doc,0);

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18.5 An example of using documents

Program DocumentFrame demonstrates the features described in the previous sec-
tions. The text is administered by an instance styledDoc of DefaultStyled-
Document .Wethen use a JTextPane to display the document. The document con-
tent is read from the ASCII file DocText.txt .Anumber of attribute sets is defined
in class DocAtt . These are then used by DocumentFrame to format parts of the
document. Also two position markers are placed in the text.
An anonymous document listener is defined in DocumentFrame and assigned to
styledDoc .Itmonitors the changes made to the document and displays them in
a DocumentStatusPanel below the document. Every insertion or deletion of text
results in a line in the status panel describing what happened. The listener also
monitors the two position markers and displays their current positions. We list
only class DocumentFrame ; the other class is on the topic's home page. Figure 18.5
shows an example.