If you have a paragraph of styled text that you would like to fit within a specific width, you can use the
LineBreakMeasurer
class. This class enables styled text to be broken into lines so that they fit within a particular visual advance. Each line is returned as aTextLayout
object, which represents unchangeable, styled character data. However, this class also enables access to layout information. ThegetAscent
andgetDescent
methods ofTextLayout
return information about the font that is used to position the lines in the component. The text is stored as anAttributedCharacterIterator
object so that the font and point size attributes can be stored with the text.The following applet positions a paragraph of styled text within a component, using
LineBreakMeasurer
,TextLayout
andAttributedCharacterIterator
.
The complete code for this applet is in
Note: If you don't see the applet running above, you need to install Java Plug-in, which happens automatically when you install the Java(TM) SE JRE or JDK. This applet requires JDK 6 or later. You can find more information on the Java Plug-in home page..
LineBreakSample.java
The following code creates an iterator with the string
vanGogh
. The start and end of the iterator is retrieved and a newLineBreakMeasurer
is created from the iterator.AttributedCharacterIterator paragraph = vanGogh.getIterator(); paragraphStart = paragraph.getBeginIndex(); paragraphEnd = paragraph.getEndIndex(); FontRenderContext frc = g2d.getFontRenderContext(); lineMeasurer = new LineBreakMeasurer(paragraph, frc);The size of the window is used to determine where the line should break. Also a
TextLayout
object is created for each line in the paragraph.// Set break width to width of Component. float breakWidth = (float)getSize().width; float drawPosY = 0; // Set position to the index of the first character in the paragraph. lineMeasurer.setPosition(paragraphStart); // Get lines from until the entire paragraph has been displayed. while (lineMeasurer.getPosition() < paragraphEnd) { TextLayout layout = lineMeasurer.nextLayout(breakWidth); // Compute pen x position. If the paragraph is right-to-left we // will align the TextLayouts to the right edge of the panel. float drawPosX = layout.isLeftToRight() ? 0 : breakWidth - layout.getAdvance(); // Move y-coordinate by the ascent of the layout. drawPosY += layout.getAscent(); // Draw the TextLayout at (drawPosX, drawPosY). layout.draw(g2d, drawPosX, drawPosY); // Move y-coordinate in preparation for next layout. drawPosY += layout.getDescent() + layout.getLeading(); }The
TextLayout
class is not frequently created directly by applications. However, this class is useful when applications need to work directly with text that has had styles (text attributes) applied at specific positions in text. For example, to draw a single word italicized in a paragraph, an application would need to perform measurements and set the font for each substring. If the text is bidirectional, this task is not so easy to do correctly. Creating aTextLayout
object from anAttributedString
object handles this problem for you. Consult the Java SE specification for more information aboutTextLayout
.