Swing/DividerSplitRatio のバックアップ(No.3)

class SplitPaneWrapper extends JPanel {
  public SplitPaneWrapper(JSplitPane splitPane) {
    super(new BorderLayout());
    this.sp = splitPane;
    add(sp);
    EventQueue.invokeLater(new Runnable() {
      @Override public void run() {
        sp.setDividerLocation(0.5);
      }
    });
  }
  private static int getOrientedSize(JSplitPane sp) {
    return (sp.getOrientation() == JSplitPane.VERTICAL_SPLIT)
      ? sp.getHeight() - sp.getDividerSize()
      : sp.getWidth()  - sp.getDividerSize();
  }
  private int prev_state = Frame.NORMAL;
  @Override public void doLayout() {
    int size = getOrientedSize(sp);
    final double proportionalLocation = sp.getDividerLocation()/(double)size;
    super.doLayout();
    if(!flag) return;
    int state = ((Frame)SwingUtilities.getWindowAncestor(sp)).getExtendedState();
    if(sp.isShowing() && state!=prev_state) {
      EventQueue.invokeLater(new Runnable() {
        @Override public void run() {
          int s = getOrientedSize(sp);
          int iv = (int)Math.round(s * proportionalLocation);
          sp.setDividerLocation(iv);
        }
      });
      prev_state = state;
    }
  }
}