Swing/LineCursor のバックアップの現在との差分(No.3)

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class LineCursorTextArea extends JTextArea {
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  private static final Color LINE_COLOR = Color.BLUE;
  private DefaultCaret caret;

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http://terai.xrea.jp/swing/linecursor/screenshot.png
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  @Override public void updateUI() {
    super.updateUI();
    caret = new DefaultCaret() {
      @Override protected synchronized void damage(Rectangle r) {
        if (r != null) {
          JTextComponent c = getComponent();
          x = 0;
          y = r.y;
          width  = c.getSize().width;
          height = r.height;
          c.repaint();
        }
      }
    };
    caret.setBlinkRate(getCaret().getBlinkRate());
    setCaret(caret);
  }

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**サンプルコード [#aed50ce8]
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 class LineCursorTextArea extends JTextArea {
   public LineCursorTextArea() {
     super();
     Caret caret = new DefaultCaret() {
       protected synchronized void damage(Rectangle r) {
         if(r!=null) {
           JTextComponent c = getComponent();
           x = 0;
           y = r.y;
           width  = c.getSize().width;
           height = r.height;
           repaint();
         }
       }
     };
     caret.setBlinkRate(getCaret().getBlinkRate());
     setCaret(caret);
   }
   protected void paintComponent(Graphics g) {
     super.paintComponent(g);
     Graphics2D g2 = (Graphics2D)g;
     Insets i = getInsets();
     int y = g2.getFontMetrics().getHeight()*getLineAtCaret(this)+i.top;
     g2.setPaint(SystemColor.activeCaption);
     g2.drawLine(i.left, y-1, getSize().width-i.left-i.right, y-1);
   }
   public static int getLineAtCaret(JTextComponent component) {
     int caretPosition = component.getCaretPosition();
     Element root = component.getDocument().getDefaultRootElement();
     return root.getElementIndex(caretPosition)+1;
   }
 }
  @Override protected void paintComponent(Graphics g) {
    super.paintComponent(g);
    Graphics2D g2 = (Graphics2D) g.create();
    Insets i = getInsets();
    int y = caret.y + caret.height - 1;
    g2.setPaint(LINE_COLOR);
    g2.drawLine(i.left, y, getSize().width - i.left - i.right, y);
    g2.dispose();
  }

-[[サンプルを起動>http://terai.xrea.jp/swing/linecursor/sample.jnlp]]
-[[jarファイル>http://terai.xrea.jp/swing/linecursor/sample.jar]]
-[[ソース>http://terai.xrea.jp/swing/linecursor/src.zip]]
  // public static int getLineAtCaret(JTextComponent component) {
  //   int caretPosition = component.getCaretPosition();
  //   Element root = component.getDocument().getDefaultRootElement();
  //   return root.getElementIndex(caretPosition) + 1;
  // }
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}
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