Swing/RubberBanding のバックアップの現在との差分(No.2)

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class RubberBandSelectionList<E extends ListItem> extends JList<E> {
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  private static final AlphaComposite ALPHA =
    AlphaComposite.getInstance(AlphaComposite.SRC_OVER, .1f);
  private RubberBandListCellRenderer<E> renderer;
  private Color polygonColor;
  public RubberBandSelectionList(ListModel<E> model) {
    super(model);
  }

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  @Override public void updateUI() {
    setSelectionForeground(null);
    setSelectionBackground(null);
    setCellRenderer(null);
    if (renderer == null) {
      renderer = new RubberBandListCellRenderer<E>();
    } else {
      removeMouseMotionListener(renderer);
      removeMouseListener(renderer);
    }
    super.updateUI();
    EventQueue.invokeLater(() -> {
      setCellRenderer(renderer);
      addMouseMotionListener(renderer);
      addMouseListener(renderer);
      setLayoutOrientation(JList.HORIZONTAL_WRAP);
      setVisibleRowCount(0);
      setFixedCellWidth(62);
      setFixedCellHeight(62);
      setBorder(BorderFactory.createEmptyBorder(5, 5, 5, 5));
    });
    Color c = getSelectionBackground();
    int r = c.getRed();
    int g = c.getGreen();
    int b = c.getBlue();
    polygonColor = r > g ? r > b ? new Color(r, 0, 0) : new Color(0, 0, b)
                         : g > b ? new Color(0, g, 0) : new Color(0, 0, b);
  }

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**サンプルコード [#t7aa984b]
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 class MyList extends JList {
   private final Color pcolor;
   private final AlphaComposite alcomp =
     AlphaComposite.getInstance(AlphaComposite.SRC_OVER, 0.1f);
   private final Polygon polygon = new Polygon();
   private final Line2D line = new Line2D.Double();
   private Point srcPoint = null;
   public MyList(ListModel model) {
     super(model);
     pcolor = makeColor();
     setLayoutOrientation(JList.HORIZONTAL_WRAP);
     setVisibleRowCount(0);
     setFixedCellWidth(62);
     setFixedCellHeight(62);
     setBorder(BorderFactory.createEmptyBorder(5,5,5,5));
     setCellRenderer(new ListCellRenderer() {
       public Component getListCellRendererComponent(JList list, Object value,
             int index, boolean isSelected, boolean cellHasFocus) {
         MyIcon icon = (MyIcon)getModel().getElementAt(index);
         icon.setSelected(isSelected);
         icon.setFocused(cellHasFocus);
         return icon;
       }
     });
     addMouseMotionListener(new MouseMotionAdapter() {
       public void mouseDragged(MouseEvent e){
         if(srcPoint==null) srcPoint = e.getPoint();
         Point destPoint = e.getPoint();
         polygon.reset();
         polygon.addPoint(srcPoint.x,  srcPoint.y);
         polygon.addPoint(destPoint.x, srcPoint.y);
         polygon.addPoint(destPoint.x, destPoint.y);
         polygon.addPoint(srcPoint.x,  destPoint.y);
         if(srcPoint.getX()==destPoint.getX() || srcPoint.getY()==destPoint.getY()) {
           line.setLine(srcPoint.getX(),srcPoint.getY(),
                        destPoint.getX(),destPoint.getY());
           setSelectedIndices(getIntersectsIcons(line));
         }else{
           setSelectedIndices(getIntersectsIcons(polygon));
         }
         repaint();
       }
     });
     addMouseListener(new MouseAdapter() {
       public void mouseReleased(MouseEvent e) {
         srcPoint = null;
         repaint();
       }
       public void mousePressed(MouseEvent e) {
         if(locationToIndex(e.getPoint())<0) {
           clearSelection();
           repaint();
         }else{
           int index = locationToIndex(e.getPoint());
           MyIcon icon = (MyIcon)getModel().getElementAt(index);
           Rectangle rect = getCellBounds(index,index);
           if(!rect.contains(e.getPoint())) {
             clearSelection();
             repaint();
           }
         }
       }
     });
   }
   public void paint(Graphics g) {
     super.paint(g);
     if(srcPoint==null) return;
     Graphics2D g2d = (Graphics2D) g;
     g2d.setColor(SystemColor.activeCaption);
     g2d.drawPolygon(polygon);
     g2d.setComposite(alcomp);
     g2d.setColor(pcolor);
     g2d.fillPolygon(polygon);
   }
   private int[] getIntersectsIcons(Shape p) {
     ListModel model = getModel();
     Vector list = new Vector(model.getSize());
     for(int i=0;i<model.getSize();i++) {
       Rectangle r = MyList.this.getCellBounds(i,i);
       if(p.intersects(r)) {
         list.add(new Integer(i));
       }
     }
     int[] il = new int[list.size()];
     for(int i=0;i<list.size();i++) {
       il[i] = ((Integer)list.get(i)).intValue();
     }
     return il;
   }
   private Color makeColor() {
     int r = SystemColor.activeCaption.getRed();
     int g = SystemColor.activeCaption.getGreen();
     int b = SystemColor.activeCaption.getBlue();
     if(r>g) {
       if(r>b) {
         return new Color(r,0,0);
       }else{
         return new Color(0,0,b);
       }
     }else{
       if(g>b) {
         return new Color(0,g,0);
       }else{
         return new Color(0,0,b);
       }
     }
   }
 }
  @Override protected void paintComponent(Graphics g) {
    super.paintComponent(g);
    if (renderer != null && renderer.polygon != null) {
      Graphics2D g2 = (Graphics2D) g.create();
      g2.setPaint(getSelectionBackground());
      g2.draw(renderer.polygon);
      g2.setComposite(ALPHA);
      g2.setPaint(polygonColor);
      g2.fill(renderer.polygon);
      g2.dispose();
    }
  }
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}
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