borderlayout.java

gcc的组建

   * @param target The container to calculate the minimum size for.
   *
   * @return The minimum size of the container
   */
  public Dimension minimumLayoutSize(Container target)
  {
    return calcSize(target, MIN);
  }

  /**
   * Returns the preferred size of the specified container using this layout.
   *
   * @param target The container to calculate the preferred size for.
   *
   * @return The preferred size of the container
   */
  public Dimension preferredLayoutSize(Container target)
  {
    return calcSize(target, PREF);
  }

  /**
   * Returns the maximum size of the specified container using this layout.
   *
   * @param target The container to calculate the maximum size for.
   *
   * @return The maximum size of the container
   */
  public Dimension maximumLayoutSize(Container target)
  {
    return calcSize(target, MAX);
  }

  /**
   * Returns the X axis alignment, which is a <code>float</code> indicating
   * where along the X axis this container wishs to position its layout.
   * 0 indicates align to the left, 1 indicates align to the right, and 0.5
   * indicates align to the center.
   *
   * @param parent The parent container.
   *
   * @return The X alignment value.
   */
  public float getLayoutAlignmentX(Container parent)
  {
    return 0.5F;
  }

  /**
   * Returns the Y axis alignment, which is a <code>float</code> indicating
   * where along the Y axis this container wishs to position its layout.
   * 0 indicates align to the top, 1 indicates align to the bottom, and 0.5
   * indicates align to the center.
   *
   * @param parent The parent container.
   *
   * @return The Y alignment value.
   */
  public float getLayoutAlignmentY(Container parent)
  {
    return 0.5F;
  }

  /**
   * Instructs this object to discard any layout information it might
   * have cached.
   *
   * @param parent The parent container.
   */
  public void invalidateLayout(Container parent)
  {
    // Nothing to do here.
  }

  /**
   * Lays out the specified container according to the constraints
   * in this object.
   *
   * @param target The container to lay out.
   */
  public void layoutContainer(Container target)
  {
    synchronized (target.getTreeLock ())
      {
        Insets i = target.getInsets();

        ComponentOrientation orient = target.getComponentOrientation ();
        boolean left_to_right = orient.isLeftToRight ();

        Component my_north = north;
        Component my_east = east;
        Component my_south = south;
        Component my_west = west;

        // Note that we currently don't handle vertical layouts.  Neither
        // does JDK 1.3.
        if (firstLine != null)
          my_north = firstLine;
        if (lastLine != null)
          my_south = lastLine;
        if (firstItem != null)
          {
            if (left_to_right)
              my_west = firstItem;
            else
              my_east = firstItem;
          }
        if (lastItem != null)
          {
            if (left_to_right)
              my_east = lastItem;
            else
              my_west = lastItem;
          }

        Dimension c = calcCompSize(center, PREF);
        Dimension n = calcCompSize(my_north, PREF);
        Dimension s = calcCompSize(my_south, PREF);
        Dimension e = calcCompSize(my_east, PREF);
        Dimension w = calcCompSize(my_west, PREF);
        int targetWidth = target.getWidth();
        int targetHeight = target.getHeight();

        /*
	<-> hgap     <-> hgap
	+----------------------------+          }
	|t                           |          } i.top
	|  +----------------------+  |  --- y1  }
	|  |n                     |  |
	|  +----------------------+  |          } vgap
	|  +---+ +----------+ +---+  |  --- y2  }        }
	|  |w  | |c         | |e  |  |                   } hh
	|  +---+ +----------+ +---+  |          } vgap   }
	|  +----------------------+  |  --- y3  }
	|  |s                     |  |
	|  +----------------------+  |          }
	|                            |          } i.bottom
	+----------------------------+          }
	|x1   |x2          |x3
	<---------------------->
	<-->         ww           <-->
	i.left                    i.right
        */

        int x1 = i.left;
        int x2 = x1 + w.width + (w.width == 0 ? 0 : hgap);
        int x3;
        if (targetWidth <= i.right + e.width)
          x3 = x2 + w.width + (w.width == 0 ? 0 : hgap);
        else
          x3 = targetWidth - i.right - e.width;
        int ww = targetWidth - i.right - i.left;

        int y1 = i.top;
        int y2 = y1 + n.height + (n.height == 0 ? 0 : vgap);
        int midh = Math.max(e.height, Math.max(w.height, c.height));
        int y3;
        if (targetHeight <= i.bottom + s.height)
          y3 = y2 + midh + vgap;
        else
          y3 = targetHeight - i.bottom - s.height;
        int hh = y3-y2-(s.height == 0 ? 0 : vgap);

        setBounds(center, x2, y2, x3-x2-(w.width == 0 ? 0 : hgap), hh);
        setBounds(my_north, x1, y1, ww, n.height);
        setBounds(my_south, x1, y3, ww, s.height);
        setBounds(my_west, x1, y2, w.width, hh);
        setBounds(my_east, x3, y2, e.width, hh);
      }
  }

  /**
   * Returns a string representation of this layout manager.
   *
   * @return A string representation of this object.
   */
  public String toString()
  {
    return getClass().getName() + "[hgap=" + hgap + ",vgap=" + vgap + "]";
  }

  /**
   * This is a convenience method to set the bounds on a component.
   * If the indicated component is null, nothing is done.
   */
  private void setBounds(Component comp, int x, int y, int w, int h)
  {
    if (comp == null)
      return;
    comp.setBounds(x, y, w, h);
  }

  private Dimension calcCompSize(Component comp, int what)
  {
    if (comp == null || !comp.isVisible())
      return new Dimension(0, 0);
    if (what == MIN)
      return comp.getMinimumSize();
    else if (what == MAX)
      return comp.getMaximumSize();
    return comp.getPreferredSize();
  }

  /**
   * This is a helper function used to compute the various sizes for
   * this layout.
   */
  private Dimension calcSize(Container target, int what)
  {
    synchronized (target.getTreeLock ())
      {
        Insets ins = target.getInsets();

        ComponentOrientation orient = target.getComponentOrientation ();
        boolean left_to_right = orient.isLeftToRight ();

        Component my_north = north;
        Component my_east = east;
        Component my_south = south;
        Component my_west = west;

        // Note that we currently don't handle vertical layouts.  Neither
        // does JDK 1.3.
        if (firstLine != null)
          my_north = firstLine;
        if (lastLine != null)
          my_south = lastLine;
        if (firstItem != null)
          {
            if (left_to_right)
              my_west = firstItem;
            else
              my_east = firstItem;
          }
        if (lastItem != null)
          {
            if (left_to_right)
              my_east = lastItem;
            else
              my_west = lastItem;
          }

        Dimension ndim = calcCompSize(my_north, what);
        Dimension sdim = calcCompSize(my_south, what);
        Dimension edim = calcCompSize(my_east, what);
        Dimension wdim = calcCompSize(my_west, what);
        Dimension cdim = calcCompSize(center, what);

        int width = edim.width + cdim.width + wdim.width + (hgap * 2);
        // Check for overflow.
        if (width < edim.width || width < cdim.width || width < cdim.width)
          width = Integer.MAX_VALUE;

        if (ndim.width > width)
          width = ndim.width;
        if (sdim.width > width)
          width = sdim.width;

        width += (ins.left + ins.right);

        int height = edim.height;
        if (cdim.height > height)
          height = cdim.height;
        if (wdim.height > height)
          height = wdim.height;

        int addedHeight = height + (ndim.height + sdim.height + (vgap * 2)
                                    + ins.top + ins.bottom);
        // Check for overflow.
        if (addedHeight < height)
          height = Integer.MAX_VALUE;
        else
          height = addedHeight;

        return(new Dimension(width, height));
      }
  }

  /**
   * Return the component at the indicated location, or null if no component
   * is at that location.  The constraints argument must be one of the 
   * location constants specified by this class.   
   * @param constraints the location
   * @return the component at that location, or null
   * @throws IllegalArgumentException if the constraints argument is not 
   * recognized
   * @since 1.5
   */
  public Component getLayoutComponent(Object constraints)
  {
    if (constraints == CENTER)
      return center;
    if (constraints == NORTH)
      return north;
    if (constraints == EAST)
      return east;
    if (constraints == SOUTH)
      return south;
    if (constraints == WEST)
      return west;
    if (constraints == PAGE_START)
      return firstLine;
    if (constraints == PAGE_END)
      return lastLine;
    if (constraints == LINE_START)
      return firstItem;
    if (constraints == LINE_END)
      return lastItem;
    throw new IllegalArgumentException("constraint " + constraints 
                                       + " is not recognized");
  }

  /**
   * Return the component at the specified location, which must be one
   * of the absolute constants such as CENTER or SOUTH.  The container's
   * orientation is used to map this location to the correct corresponding
   * component, so for instance in a right-to-left container, a request
   * for the EAST component could return the LINE_END component.  This will
   * return null if no component is available at the given location.
   * @param container the container whose orientation is used
   * @param constraints the absolute location of the component
   * @return the component at the location, or null
   * @throws IllegalArgumentException if the constraint is not recognized
   */
  public Component getLayoutComponent(Container container, Object constraints)
  {
    ComponentOrientation orient = container.getComponentOrientation();
    if (constraints == CENTER)
      return center;
    // Note that we don't support vertical layouts.
    if (constraints == NORTH)
      return north;
    if (constraints == SOUTH)
      return south;
    if (constraints == WEST)
      {
        // Note that relative layout takes precedence.
        if (orient.isLeftToRight())
          return firstItem == null ? west : firstItem;
        return lastItem == null ? west : lastItem;
      }
    if (constraints == EAST)
      {
        // Note that relative layout takes precedence.
        if (orient.isLeftToRight())
          return lastItem == null ? east : lastItem;
        return firstItem == null ? east : firstItem;
      }
    throw new IllegalArgumentException("constraint " + constraints
                                       + " is not recognized");
  }

  /**
   * Return the constraint corresponding to a component in this layout.
   * If the component is null, or is not in this layout, returns null.
   * Otherwise, this will return one of the constraint constants defined
   * in this class.
   * @param c the component
   * @return the constraint, or null
   * @since 1.5
   */
  public Object getConstraints(Component c)
  {
    if (c == null)
      return null;
    if (c == center)
      return CENTER;
    if (c == north)
      return NORTH;
    if (c == east)
      return EAST;
    if (c == south)
      return SOUTH;
    if (c == west)
      return WEST;
    if (c == firstLine)
      return PAGE_START;
    if (c == lastLine)
      return PAGE_END;
    if (c == firstItem)
      return LINE_START;
    if (c == lastItem)
      return LINE_END;
    return null;
  }
}