listbox.java

图论中关于简单无向图的深度

/**
 * <p>Title: </p>
 * <p>Description: </p>
 * <p>Copyright: Copyright (c) 2005</p>
 * <p>Company: </p>
 * @author not attributable
 * @version 1.0
 */
import java.awt.*;
import java.awt.event.*;

public class ListBox extends JavaBookDialog implements ActionListener{
  //----------------------------------
//    Data Members:
//----------------------------------

     /**
      * Nothing is selected
      */
     public static final  int     NO_SELECTION  = -1;

     /**
      * The Cancel button is pressed
      */
     public static final  int     CANCEL        = -2;

     /**
      * Nothing is selected
      */
     public static final  String  NO_ITEM       = null;

     /**
      * OK button is pressed
      */
     private static final int 	 ACTION_OK     =  0;

     /**
      * Cancel button is pressed
      */
     private static final int 	 ACTION_CANCEL = -1;

     /**
      * The actual object that contains the list of items
      */
     private List    list;

     /**
      * The OK buton
      */
     private Button  okButton;

     /**
      * The Cancel button
      */
     private Button  cancelButton;

     /**
      * Tells which of the two buttons is clicked
      */
     private int     status;


//-----------------------------------
//    Constructors
//-----------------------------------

     /**
      * Creates a modal dialog with a default title.
      *
      * @param owner any Frame object, but most commonly expected is a MainWindow object
      *
      */
     public ListBox(Frame owner)
     {
         this(owner,"Select One:",true);
     }

     /**
      * Creates a modal dialog with its title set to the second parameter.
      *
      * @param owner any Frame object, but most commonly expected is a MainWindow object
      * @param text  the title of this dialog
      *
      */
     public ListBox(Frame owner, String text)
     {
         this(owner,text,true);
     }

     /**
      * Creates a modal or modeless dialog with a default title.
      *
      * @param owner any Frame object, but most commonly expected is a MainWindow object
      * @param modal <code>true</code> for modal and <code>false</code> for modeless dialog
      *
      */
     public ListBox(Frame owner, boolean modal)
     {
         this(owner,"Select One:",modal);
     }

     /**
      * Creates a modal or modeless dialog with its title set to the second parameter.
      *
      * @param owner any Frame object, but most commonly expected is a MainWindow object
      * @param text  the title of this dialog
      * @param modal <code>true</code> for modal and <code>false</code> for modeless dialog
      *
      */
     public ListBox(Frame owner, String text, boolean modal)
     {
         super(owner,modal);
         setTitle(text);
         initialize();
     }


//-----------------------------------------------
//    Public Methods:
//
//        void    actionPerformed     ( ActionEvent   ) Note: Do not call this method
//        void    addItem             ( String        )
//        void    deleteItem          ( int           )
//        void    deleteItem          ( String        )
//
//        int     getSelectedIndex    (               )
//        String  getItemFromIndex    ( int           )
//        String  getSelectedItem     (		          )
//
//        boolean isCanceled          (               )
//
//        void    windowClosing	      ( WindowEvent   ) Note: Do not call this method
//
//-----------------------------------------------

     /**
      * Implements the required method of the ActionListener. Do not call this
      * method. The Java virtual machine handles the action event processing.
      * This method sets the status to ACTION_OK or ACTION_CANCEL depending on
      * which button is clicked.
      *
      * @param e the ActionEvent object.
      *
      */
     public void actionPerformed(ActionEvent e)
     {
         if (e.getSource() == okButton) {
             //close the dialog
             setVisible(false);
             status = ACTION_OK;
         }
         else if (e.getSource() == cancelButton) {
             setVisible(false);
             status = ACTION_CANCEL;
         }
     }

     /**
      * Adds a new item to the list.
      *
      * @param item a String value to be added to the list
      */
     public void addItem(String item)
     {
         list.add(item);
     }

     /**
      * Deletes an item from the list. The item to remove is identified
      * by its position index in the list.
      *
      * @param index the position of an item to be removed
      */
     public void deleteItem(int index)
     {
         list.remove(index);
     }

     /**
      * Deletes an item from the list. The item (String) to remove is identified
      * by its value.
      *
      * @param item an item to be removed
      */
     public void deleteItem(String item)
     {
         //search for an item in the list
         int i       = 0;
         int length  = list.getItemCount();

         while (i < length && list.getItem(i) != item) {
             i++;
         }

         if (i < length) {
             //found, so delete it
             list.remove(i);
         }

         //if not found, do nothing
     }

     /**
      * Returns the position of the item selected. If the OK button was
      * clicked, then the method returns the index of the selected item. If the
      * Cancel button was clicked, then this method returns NO_SELECTION.
      *
      * @return status of the user selection
      */
     public int getSelectedIndex()
     {
         showIt();
         if (status == ACTION_OK)  {
             return list.getSelectedIndex();
             //returns NO_SELECTION if nothing is selected
         }
         else if (status == ACTION_CANCEL) {
             return CANCEL; // user closed with Cancel button
             //NOTE: returns CANCEL if canceled
         }
         else {
             return NO_SELECTION;
             //NOTE: returns NO_SELECTION if closed without selecting an item.
         }
     }


     /**
      * Returns an item at the specified location in the list. This method
      * returns an item at the designated position whether the item is selected
      * or not.
      *
      * @param index position of an item in the list
      *
      * @return the specified item in the list
      */
     public String getItemFromIndex(int index)
     {
        return list.getItem(index);
     }

     /**
      * Returns the selected item if any. Appropriate status is returned
      * if no item is selected.
      *
      * return the item selected by the user
      */
     public String getSelectedItem()
     {
         showIt();
         if (status == ACTION_OK) {
             return list.getSelectedItem();
             //returns NO_ITEM if nothing is selected
         }
         else {
             return NO_ITEM;
             //NOTE: returns NO_ITEM if canceled, closed,
             //      or okayed without selecting an item.
         }
     }

     /**
      * Returns true if this dialog is canceled by the user
      *
      * @return true if this dialog is canceled
      */
     public boolean isCanceled( )
     {
         if (status == ACTION_CANCEL) {
             return true;
         }
         else {
             return false;
         }
     }

     /**
      * The standard event handler for window closing event. This dialog
      * is closed when the window closing event occurs.
      */
     public void windowClosing(WindowEvent e)
     {
         dispose();
         status = ACTION_CANCEL;
     }


//-----------------------------------------------
//    Protected Methods:
//
//            void    adjustSize      (           )
//
//-----------------------------------------------

     /**
      * Adjusts the dialog. Nothing is in this method because the Panel object
      * is used for layout.
      */
     protected void adjustSize()
     {
     }


//-----------------------------------------------
//    Private Methods:
//
//       void    initialize      (           )
//       void    showIt          (           )
//
//-----------------------------------------------

    /**
     * Initializes the components in this ListBox. Uses a Panel to put
     * the components, instead of absolute positioning.
     */
    private void initialize()
    {
        setResizable(false);
        setSize(170,200);

        list = new List();
        list.setFont(font);
        add("Center",list);

        Panel p = new Panel();

        okButton     = new Button("  OK  ");
        okButton.addActionListener(this);
        cancelButton = new Button("Cancel");
        cancelButton.addActionListener(this);
        p.add(okButton);
        p.add(cancelButton);
        add("South",p);

        addWindowListener(this);
        moveToCenter();
    }

    /**
     * Shows this ListBox on the screen. Before showing, this method
     * removes the previous selection if there is one.
     */
    private void showIt()
    {
        //deselect any previously selected item
        int index = list.getSelectedIndex();
        if (index >=0) {
            list.deselect(index);
        }

        super.setVisible(true);
    }

 }