Automatically Updating Styled Text When a Style Is Updated
When a style is applied to text in a text pane, the text is set with
the attributes of the style. If the style is changed, the set of
attributes associated with the range of text does not change.
This example demonstrates how to have styled text automatically
updated when the style object used to style the text is changed. When
a named style is applied to text, the name of the style is included in
the set of attributes that are associated with the text. Hence, it is
possible to find all the places where a named style has been applied
in a text pane. The reapplyStyle() method takes a style object
and searches the text pane for all uses of the style (by name) and
reapplies it.
In order to detect changes to a style, a change listener is
added to it. Whenever the style is changed, the style's change
listener will call reapplyStyle() to update the text pane.
final JTextPane textPane = new JTextPane();
ChangeListener changeListener = new ChangeListener() {
public void stateChanged(ChangeEvent e) {
reapplyStyles(textPane, (Style)e.getSource());
}
};
// Make paragraph red
Style style = textPane.addStyle("Highlight", null);
style.addChangeListener(changeListener);
StyleConstants.setForeground(style, Color.red);
textPane.setParagraphAttributes(style, true);
// paragraph appears red
style = textPane.getStyle("Highlight");
StyleConstants.setUnderline(style, true);
// paragraph becomes red and underlined
// This method traverses every paragraph and content element
// and reapplies any style that matches the specified style
public static void reapplyStyles(JTextPane c, Style style) {
// Get section element
Element sectionElem = c.getDocument().getDefaultRootElement();
// Get number of paragraphs.
int paraCount = sectionElem.getElementCount();
for (int i=0; i<paraCount; i++) {
Element paraElem = sectionElem.getElement(i);
AttributeSet attr = paraElem.getAttributes();
// Get the name of the style applied to this paragraph element; may be null
String sn = (String)attr.getAttribute(StyleConstants.NameAttribute);
// Check if style name match
if (style.getName().equals(sn)) {
// Reapply the paragraph style
int rangeStart = paraElem.getStartOffset();
int rangeEnd = paraElem.getEndOffset();
c.getStyledDocument().setParagraphAttributes(
rangeStart, rangeEnd-rangeStart, style, true);
}
// Enumerate the content elements
for (int j=0; j<paraElem.getElementCount(); j++) {
Element contentElem = paraElem.getElement(j);
attr = contentElem.getAttributes();
// Get the name of the style applied to this content element; may be null
sn = (String)attr.getAttribute(StyleConstants.NameAttribute);
// Check if style name match
if (style.getName().equals(sn)) {
// Reapply the content style
int rangeStart = contentElem.getStartOffset();
int rangeEnd = contentElem.getEndOffset();
c.getStyledDocument().setCharacterAttributes(
rangeStart, rangeEnd-rangeStart, style, true);
}
}
}
}
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