basicscrollpaneui.java

gcc的组建

   */
  MouseWheelListener mouseWheelListener;

  public static ComponentUI createUI(final JComponent c) 
  {
    return new BasicScrollPaneUI();
  }

  protected void installDefaults(JScrollPane p)
  {
    scrollpane = p;
    LookAndFeel.installColorsAndFont(p, "ScrollPane.background",
                                     "ScrollPane.foreground",
                                     "ScrollPane.font");
    LookAndFeel.installBorder(p, "ScrollPane.border");
    p.setOpaque(true);
  }

  protected void uninstallDefaults(JScrollPane p)
  {
    p.setForeground(null);
    p.setBackground(null);
    p.setFont(null);
    p.setBorder(null);
    scrollpane = null;
  }
    
  public void installUI(final JComponent c) 
  {
    super.installUI(c);
    installDefaults((JScrollPane) c);
    installListeners((JScrollPane) c);
    installKeyboardActions((JScrollPane) c);
  }

  /**
   * Installs the listeners on the scrollbars, the viewport and the scrollpane.
   *
   * @param sp the scrollpane on which to install the listeners
   */
  protected void installListeners(JScrollPane sp)
  {
    if (spPropertyChangeListener == null)
      spPropertyChangeListener = createPropertyChangeListener();
    sp.addPropertyChangeListener(spPropertyChangeListener);

    if (hsbChangeListener == null)
      hsbChangeListener = createHSBChangeListener();
    sp.getHorizontalScrollBar().getModel().addChangeListener(hsbChangeListener);
    
    if (vsbChangeListener == null)
      vsbChangeListener = createVSBChangeListener();
    sp.getVerticalScrollBar().getModel().addChangeListener(vsbChangeListener);

    if (viewportChangeListener == null)
      viewportChangeListener = createViewportChangeListener();
    sp.getViewport().addChangeListener(viewportChangeListener);

    if (mouseWheelListener == null)
      mouseWheelListener = createMouseWheelListener();
    sp.addMouseWheelListener(mouseWheelListener);
  }

  /**
   * Installs additional keyboard actions on the scrollpane. This is a hook
   * method provided to subclasses in order to install their own keyboard
   * actions.
   *
   * @param sp the scrollpane to install keyboard actions on
   */
  protected void installKeyboardActions(JScrollPane sp)
  {
    // TODO: Is this only a hook method or should we actually do something
    // here? If the latter, than figure out what and implement this.
  }

  /**
   * Creates and returns the change listener for the horizontal scrollbar.
   *
   * @return the change listener for the horizontal scrollbar
   */
  protected ChangeListener createHSBChangeListener()
  {
    return new HSBChangeListener();
  }

  /**
   * Creates and returns the change listener for the vertical scrollbar.
   *
   * @return the change listener for the vertical scrollbar
   */
  protected ChangeListener createVSBChangeListener()
  {
    return new VSBChangeListener();
  }

  /**
   * Creates and returns the change listener for the viewport.
   *
   * @return the change listener for the viewport
   */
  protected ChangeListener createViewportChangeListener()
  {
    return new ViewportChangeHandler();
  }

  /**
   * Creates and returns the property change listener for the scrollpane.
   *
   * @return the property change listener for the scrollpane
   */
  protected PropertyChangeListener createPropertyChangeListener()
  {
    return new PropertyChangeHandler();
  }

  /**
   * Creates and returns the mouse wheel listener for the scrollpane.
   *
   * @return the mouse wheel listener for the scrollpane
   */
  protected MouseWheelListener createMouseWheelListener()
  {
    return new MouseWheelHandler();
  }

  public void uninstallUI(final JComponent c) 
  {
    super.uninstallUI(c);
    this.uninstallDefaults((JScrollPane)c);
    uninstallListeners((JScrollPane) c);
    installKeyboardActions((JScrollPane) c);
  }

  /**
   * Uninstalls all the listeners that have been installed in
   * {@link #installListeners(JScrollPane)}.
   *
   * @param c the scrollpane from which to uninstall the listeners 
   */
  protected void uninstallListeners(JComponent c)
  {
    JScrollPane sp = (JScrollPane) c;
    sp.removePropertyChangeListener(spPropertyChangeListener);
    sp.getHorizontalScrollBar().getModel()
                               .removeChangeListener(hsbChangeListener);
    sp.getVerticalScrollBar().getModel()
                             .removeChangeListener(vsbChangeListener);
    sp.getViewport().removeChangeListener(viewportChangeListener);
    sp.removeMouseWheelListener(mouseWheelListener);
  }

  /**
   * Uninstalls all keyboard actions from the JScrollPane that have been
   * installed by {@link #installKeyboardActions}. This is a hook method
   * provided to subclasses to add their own keyboard actions.
   *
   * @param sp the scrollpane to uninstall keyboard actions from
   */
  protected void uninstallKeyboardActions(JScrollPane sp)
  {
    // TODO: Is this only a hook method or should we actually do something
    // here? If the latter, than figure out what and implement this.
  }

  public Dimension getMinimumSize(JComponent c) 
  {
    JScrollPane p = (JScrollPane ) c;
    ScrollPaneLayout sl = (ScrollPaneLayout) p.getLayout();
    return sl.minimumLayoutSize(c);
  }

  public void paint(Graphics g, JComponent c)
  {      
    // do nothing; the normal painting-of-children algorithm, along with
    // ScrollPaneLayout, does all the relevant work.
  }

  /**
   * Synchronizes the scrollbars with the viewport's extents.
   */
  protected void syncScrollPaneWithViewport()
  {
    JViewport vp = scrollpane.getViewport();

    // Update the horizontal scrollbar.
    JScrollBar hsb = scrollpane.getHorizontalScrollBar();
    hsb.setMaximum(vp.getViewSize().width);
    hsb.setValue(vp.getViewPosition().x);
    hsb.setVisibleAmount(vp.getExtentSize().width);
    
    // Update the vertical scrollbar.
    JScrollBar vsb = scrollpane.getVerticalScrollBar();
    vsb.setMaximum(vp.getViewSize().height);
    vsb.setValue(vp.getViewPosition().y);
    vsb.setVisibleAmount(vp.getExtentSize().height);
  }

  /**
   * Receives notification when the <code>columnHeader</code> property has
   * changed on the scrollpane.
   *
   * @param ev the property change event
   */
  protected void updateColumnHeader(PropertyChangeEvent ev)
  {
    // TODO: Find out what should be done here. Or is this only a hook?
  }

  /**
   * Receives notification when the <code>rowHeader</code> property has changed
   * on the scrollpane.
   *
   * @param ev the property change event
   */
  protected void updateRowHeader(PropertyChangeEvent ev)
  {
    // TODO: Find out what should be done here. Or is this only a hook?
  }

  /**
   * Receives notification when the <code>scrollBarDisplayPolicy</code>
   * property has changed on the scrollpane.
   *
   * @param ev the property change event
   */
  protected void updateScrollBarDisplayPolicy(PropertyChangeEvent ev)
  {
    // TODO: Find out what should be done here. Or is this only a hook?
  }

  /**
   * Receives notification when the <code>viewport</code> property has changed
   * on the scrollpane.
   *
   * This method sets removes the viewportChangeListener from the old viewport
   * and adds it to the new viewport.
   *
   * @param ev the property change event
   */
  protected void updateViewport(PropertyChangeEvent ev)
  {
    JViewport oldViewport = (JViewport) ev.getOldValue();
    oldViewport.removeChangeListener(viewportChangeListener);
    JViewport newViewport = (JViewport) ev.getNewValue();
    oldViewport.addChangeListener(viewportChangeListener);
  }
}