The Net: Ultimate Internet Guide/WWLCD1.ISO/pc/java/un2maiq4/pjjava/src/pj/awt/pagestack.java

Java Source | 1996-08-14 | 5.4 KB | 220 lines

/*---------------------------------------------------------------------------

    Written by the Personal Journal developers of Dow Jones & Company, Inc.

    Dow Jones makes no representations or warranties about
    the suitability of this software, either express or
    implied, including but not limited to the implied warranties
    of merchantability, fitness for a particular purpose,
    or non-infringement.  Dow Jones will not be liable for
    any damages suffered by a user as a result of using,
    modifying or distributing this software or its derivatives.


    @(#)PageStack.java

        A container of Pages in which the pages are stacked on top of each
        other.


    Authors:

        rphall          Rick Hall


    Version Ident:

        $Header$


    History:

        04-Jan-1995 rphall  Initial Creation
        27-Mar-1996    Ted S.    Added conversion from name to index.
        28-Mar-1996    Ted S.    Added getPage().

---------------------------------------------------------------------------*/

package pj.awt;

import pj.awt.Page;

import collections.Assertable;
import collections.ImplementationCheckable;
import collections.ImplementationError;
import java.awt.CardLayout;
import java.awt.Component;
import java.awt.Panel;

/**
 * A container of Pages in which the pages are stacked on top of each
 * other.
 * <P>
 * A PageStack maintains Pages in a sequence.  The page sequence is set
 * by the order in which Pages are appended to a stack: the first page
 * appended to the stack is the first page in the sequence; the last page
 * appended to the stack is the last page in the sequence.
 * <P>
 * A PageStack has a cursor into the sequence of pages.  The cursor is
 * called the current page.  The page to which the cursor points is the page
 * that appears topmost to a user.  Moving the current page cursor changes
 * the page that a user sees.  The current page cursor may be moved
 * sequentially through a page stack by first, next, last, and previous
 * operations. The current page cursor may be moved to specific page by
 * the setCurrentPage operation.
 *
 * @see     pj.awt.Page
 * @see     pj.awt.Notebook
 * @version 0.00 04-Jan-96
 * @author  rphall
*/
public class PageStack extends Panel implements Assertable
    {

    // --- Instance variables

    protected CardLayout clLayout;


    // --- Public constructors

    /**
     * Construct a PageStack
    */
    public PageStack()
        {
        clLayout = new CardLayout();
        setLayout( clLayout );
        }

    // --- Public operations

    public void appendPage(Page page)
        {
        add(page.getName(),page);
        }

    public int countPages()
        {
        return countComponents();
        }

    public Page page()
        {
        // Current page is the only visible component
        Component c = null;
        for (int i=0; i<countComponents(); i++)
            {
            c = getComponent(i);
            if ( c.isVisible() )
                {
                assert(c instanceof Page);
                break;
                } // if visible

            } // for

        return (Page)c;
        } // page()

    public Page page(String name)
        {
        clLayout.show(this,name);
        return page();
        }

    public Page firstPage()
        {
        clLayout.first(this);
        return page();
        }

    public Page nextPage()
        {
        clLayout.next(this);
        return page();
        }

    public Page previousPage()
        {
        clLayout.previous(this);
        return page();
        }

    public Page lastPage()
        {
        clLayout.last(this);
        return page();
        }


    // Return a reference to the n'th page.
    // This index is 1 based.
    public Page getPage( int Index )
        {
        Component[] PageList = getComponents();

        if ( ( Index >= 1 ) && ( Index <= PageList.length ) )
            return ((Page)PageList[Index - 1]);
        else
            return null;
        }

    // Return the index (  1 based ) of the current page.
    public int currPage()
        {
        return PageNameToIndex( page().getName() );
        }

    // Find the index of the page with the given name.
    // Index is 1 based.
    public int PageNameToIndex( String name )
        {
        int nRet = 0;
        Component[] PageList;

        // Step through all pages, until
        // I find the one with matching name.
        // Then I return it's index.
        PageList = getComponents();

        while ( ( name != ((Page)PageList[nRet]).getName() ) && ( nRet < ( PageList.length - 1 ) ) )
            {
            nRet ++;
            }

        // Index is 1 based.
        return nRet + 1;
        }


    /**
     * Raise an exception if predicate is false.
     * @see collections.Assertable
    */
    public void assert(boolean predicate) throws ImplementationError
        {
        ImplementationError.assert(this, predicate);
        }

    /**
     * Checks if all components of a PageStack are Pages.
     * @see collections.ImplementationCheckable
     * @exception ImplementationError Thrown if any component is
     * not a Page.
    */
    public void checkImplementation() throws ImplementationError
        {
        Component c = null;
        for (int i=0; i<countComponents(); i++)
            {
            c = getComponent(i);
            assert(c instanceof Page);
            } // for

        } // checkImplementation



    } // PageStack