menucomponent.java

gcc的组建

/**
 * Returns a debugging string for this component
 */
protected String
paramString()
{
  return "name=" + getName();
}

/**
 * Gets the AccessibleContext associated with this <code>MenuComponent</code>.
 * As an abstract class, we return null.  Concrete subclasses should return
 * their implementation of the accessibility context.
 *
 * @return null.
 */

public AccessibleContext getAccessibleContext()
{
  return null;
}

/**
 * This class provides a base for the accessibility support of menu
 * components.
 *
 * @author Andrew John Hughes ([e-mail])
 */
protected abstract class AccessibleAWTMenuComponent
  extends AccessibleContext
  implements Serializable, AccessibleComponent, AccessibleSelection
{

  /**
   * Compatible with JDK 1.4.2 revision 5
   */
  private static final long serialVersionUID = -4269533416223798698L;

  /**
   * This is the default constructor.  It should be called by
   * concrete subclasses to ensure necessary groundwork is completed.
   */
  protected AccessibleAWTMenuComponent()
  {
  }

  /**
   * Replaces or supplements the component's selection with the
   * <code>Accessible</code> child at the supplied index.  If
   * the component supports multiple selection, the child is
   * added to the current selection.  Otherwise, the current
   * selection becomes the specified child.  If the child is
   * already selected, nothing happens.
   * <br />
   * <br />
   * As the existence of children can not be determined from
   * this abstract class, the implementation of this method
   * is left to subclasses.
   *
   * @param index the index of the specified child within a
   *        zero-based list of the component's children.
   */
  public void addAccessibleSelection(int index)
  {
    /* Subclasses with children should implement this */
  }

  /**
   * Registers the specified focus listener to receive
   * focus events from this component.
   *
   * @param listener the new focus listener.
   */
  public void addFocusListener(FocusListener listener)
  {
    /*
     * Chain the new focus listener to the existing chain
     * of focus listeners.  Each new focus listener is
     * coupled via multicasting to the existing chain.
     */
    focusListener = AWTEventMulticaster.add(focusListener, listener);
  }

  /**
   * Clears the component's current selection.  Following
   * the calling of this method, no children of the component
   * will be selected.
   * <br />
   * <br />
   * As the existence of children can not be determined from
   * this abstract class, the implementation of this method
   * is left to subclasses.
   */
  public void clearAccessibleSelection()
  {
  }

  /**
   * Returns true if the specified point lies within the
   * component.  The supplied co-ordinates are assumed to
   * be relative to the co-ordinate system of the component
   * itself.  Thus, the point (0,0) is the upper left corner
   * of this component.
   * <br />
   * <br />
   * Please note that this method depends on a correctly implemented
   * version of the <code>getBounds()</code> method.  Subclasses
   * must provide the bounding rectangle via <code>getBounds()</code>
   * in order for this method to work.  
   *
   * @param point the point to check against this component.
   * @return true if the point is within this component.
   * @see #getBounds()
   */
  public boolean contains(Point point)
  {
    /* 
       We can simply return the result of a
       test for containment in the bounding rectangle 
    */
    return getBounds().contains(point);
  }

  /**
   * Returns the <code>Accessible</code> child of this component present
   * at the specified point.  The supplied co-ordinates are
   * assumed to be relative to the co-ordinate system of this
   * component (the parent of any returned accessible).  Thus,
   * the point (0,0) is the upper left corner of this menu
   * component.
   * <br />
   * <br />
   * As the existence of children can not be determined from
   * this abstract class, the implementation of this method
   * is left to subclasses.
   * 
   * @param point the point at which the returned accessible
   *        is located.
   * @return null.
   */
  public Accessible getAccessibleAt(Point point)
  {
    return null;
  }

  /**
   * Returns the <code>Accessible</code> child at the supplied
   * index within the list of children of this component.
   * <br />
   * <br />
   * As the existence of children can not be determined from
   * this abstract class, the implementation of this method
   * is left to subclasses.
   *
   * @param index the index of the <code>Accessible</code> child
   *        to retrieve.
   * @return null.
   */
  public Accessible getAccessibleChild(int index)
  {
    return null;
  }

  /**
   * Returns the number of children of this component which
   * implement the <code>Accessible</code> interface.  If
   * all children of this component are accessible, then
   * the returned value will be the same as the number of
   * children.
   * <br />
   * <br />
   *
   * @return 0.
   */
  public int getAccessibleChildrenCount()
  {
    return 0;
  }

  /**
   * Retrieves the <code>AccessibleComponent</code> associated
   * with this accessible context and its component.  As the
   * context itself implements <code>AccessibleComponent</code>,
   * this is the return value.
   *
   * @return the context itself.
   */
  public AccessibleComponent getAccessibleComponent()
  {
    return this;
  }

  /**
   * Returns the accessible name for this menu component.  This
   * is the name given to the component, which may be null if
   * not set using <code>setName()</code>.
   * <br />
   * <br />
   * The name is not the most appropriate description of this
   * object.  Subclasses should preferably provide a more
   * accurate description.  For example, a File menu could
   * have the description `Lists commands related to the
   * file system'.
   *
   * @return a description of the component.  Currently,
   *         this is just the contents of the name property.
   * @see MenuComponent#setName(String)
   */
  public String getAccessibleDescription()
  {
    return MenuComponent.this.getName();
  }

  /**
   * Retrieves the index of this component within its parent.
   * If no parent exists, -1 is returned.
   *
   * @return -1 as the parent, a <code>MenuContainer</code>
   *         is not <code>Accessible</code>.
   */
  public int getAccessibleIndexInParent()
  {
    return -1;
  }

  /**
   * Returns the accessible name of this component.  This
   * is the name given to the component, which may be null if
   * not set using <code>setName()</code>.
   * <br />
   * <br />
   * The name property is not the most suitable string to return
   * for this method.  The string should be localized, and
   * relevant to the operation of the component.  For example,
   * it could be the text of a menu item.  However, this can
   * not be used at this level of abstraction, so it is the
   * responsibility of subclasses to provide a more appropriate
   * name.
   *
   * @return a localized name for this component.  Currently, this
   *         is just the contents of the name property.
   * @see MenuComponent#setName(String)
   */
  public String getAccessibleName()
  {
    return MenuComponent.this.getName();
  }

  /**
   * Returns the <code>Accessible</code> parent of this component.
   * As the parent of a <code>MenuComponent</code> is a
   * <code>MenuContainer</code>, which doesn't implement
   * <code>Accessible</code>, this method returns null.
   *
   * @return null.
   */
  public Accessible getAccessibleParent()
  {
    return null;
  }

  /**
   * Returns the accessible role of this component.
   * <br />
   * <br />
   * The abstract implementation of this method returns
   * <code>AccessibleRole.AWT_COMPONENT</code>,
   * as the abstract component has no specific role.  This
   * method should be overridden by concrete subclasses, so
   * as to return an appropriate role for the component.
   *
   * @return <code>AccessibleRole.AWT_COMPONENT</code>.
   */
  public AccessibleRole getAccessibleRole()
  {
    return AccessibleRole.AWT_COMPONENT;
  }

  /**
   * Retrieves the <code>AccessibleSelection</code> associated
   * with this accessible context and its component.  As the
   * context itself implements <code>AccessibleSelection</code>,
   * this is the return value.
   *
   * @return the context itself.
   */
  public AccessibleSelection getAccessibleSelection()
  {
    return this;
  }

  /**
   * Retrieves the <code>Accessible</code> selected child
   * at the specified index.  If there are no selected children
   * or the index is outside the range of selected children,
   * null is returned.  Please note that the index refers
   * to the index of the child in the list of <strong>selected
   * children</strong>, and not the index of the child in
   * the list of all <code>Accessible</code> children.
   * <br />
   * <br />
   * As the existence of children can not be determined from
   * this abstract class, the implementation of this method
   * is left to subclasses.
   *
   * @param index the index of the selected <code>Accessible</code>
   *        child.
   */
  public Accessible getAccessibleSelection(int index)
  {
    return null;
  }

  /**
   * Returns a count of the number of <code>Accessible</code>
   * children of this component which are currently selected.
   * If there are no children currently selected, 0 is returned.
   * <br />
   * <br />
   * As the existence of children can not be determined from
   * this abstract class, the implementation of this method
   * is left to subclasses.
   *
   * @return 0.
   */
  public int getAccessibleSelectionCount()
  {
    return 0;
  }

  /**
   * Retrieves the current state of this component
   * in an accessible form.  For example, a given component
   * may be visible, selected, disabled, etc.
   * <br />
   * <br />
   * As this class tells us virtually nothing about the component,
   * except for its name and font, no state information can be
   * provided.  This implementation thus returns an empty
   * state set, and it is left to concrete subclasses to provide
   * a more acceptable and relevant state set.  Changes to these
   * properties also need to be handled using
   * <code>PropertyChangeListener</code>s.
   *
   * @return an empty <code>AccessibleStateSet</code>.
   */
  public AccessibleStateSet getAccessibleStateSet()
  {
    return new AccessibleStateSet();
  }

  /**
   * Returns the background color of the component, or null
   * if this property is unsupported.
   * <br />
   * <br />
   * This abstract class knows nothing about how the component
   * is drawn on screen, so this method simply returns the
   * default system background color used for rendering menus.
   * Concrete subclasses which handle the drawing of an onscreen
   * menu component should override this method and provide
   * the appropriate information.
   *
   * @return the default system background color for menus.
   * @see #setBackground(java.awt.Color)
   */
  public Color getBackground()
  {
    return SystemColor.menu;
  }

  /**
   * Returns a <code>Rectangle</code> which represents the
   * bounds of this component.  The returned rectangle has the
   * height and width of the component's bounds, and is positioned
   * at a location relative to this component's parent, the
   * <code>MenuContainer</code>.  null is returned if bounds
   * are not supported by the component.
   * <br />
   * <br />
   * This abstract class knows nothing about how the component
   * is drawn on screen, so this method simply returns null.
   * Concrete subclasses which handle the drawing of an onscreen
   * menu component should override this method and provide
   * the appropriate information.
   *
   * @return null.
   * @see #setBounds(java.awt.Rectangle)
   */
  public Rectangle getBounds()
  {
    return null;
  }

  /**
   * Returns the <code>Cursor</code> displayed when the pointer
   * is positioned over this component.  Alternatively, null
   * is returned if the component doesn't support the cursor
   * property.
   * <br />
   * <br />
   * This abstract class knows nothing about how the component
   * is drawn on screen, so this method simply returns the default
   * system cursor.  Concrete subclasses which handle the drawing
   * of an onscreen menu component may override this method and provide
   * the appropriate information.
   *
   * @return the default system cursor.
   * @see #setCursor(java.awt.Cursor)
   */
  public Cursor getCursor()
  {
    return Cursor.getDefaultCursor();
  }

  /**
   * Returns the <code>Font</code> used for text created by this component.
   *
   * @return the current font.
   * @see #setFont(java.awt.Font)
   */
  public Font getFont()
  {
    return MenuComponent.this.getFont();
  }

  /**
   * Retrieves information on the rendering and metrics of the supplied
   * font.  If font metrics are not supported by this component, null
   * is returned.
   * <br />
   * <br />
   * The abstract implementation of this method simply uses the toolkit
   * to obtain the <code>FontMetrics</code>.  Concrete subclasses may
   * find it more efficient to invoke their peer class directly, if one
   * is available.
   *
   * @param font the font about which to retrieve rendering and metric
   *        information.
   * @return the metrics of the given font, as provided by the system
   *         toolkit.
   * @throws NullPointerException if the supplied font was null.