weatherdisplay.java

高级java2 大学教程(含源码,经典的Java学习教程

// WeatherDisplay.java
// WeatherDisplay extends JPanel to display results
// of client's request for weather conditions.
package com.deitel.advjhtp1.jms.weather;

// Java core packages
import java.awt.*;
import java.awt.event.*;
import java.util.*;

// Java extension packages
import javax.swing.*;

// Deitel packages
import com.deitel.advjhtp1.rmi.weather.*;

public class WeatherDisplay extends JPanel {

   // WeatherListModel and Map for storing WeatherBeans
   private WeatherListModel weatherListModel;
   private Map weatherItems;

   // WeatherDisplay constructor
   public WeatherDisplay()
   {
      setLayout( new BorderLayout() );
      
      ImageIcon headerImage = new ImageIcon( 
         WeatherDisplay.class.getResource( 
            "images/header.jpg" ) );
      add( new JLabel( headerImage ), BorderLayout.NORTH );

      // use JList to display updated weather conditions
      // for requested cities
      weatherListModel = new WeatherListModel();
      JList weatherJList = new JList( weatherListModel );
      weatherJList.setCellRenderer( new WeatherCellRenderer() );

      add( new JScrollPane( weatherJList ), BorderLayout.CENTER );

      // maintain WeatherBean items in HashMap 
      weatherItems = new HashMap();
      
   } // end WeatherDisplay constructor

   // add WeatherBean item to display
   public void addItem( WeatherBean weather )
   {
      String city = weather.getCityName();

      // check whether city is already in display
      if ( weatherItems.containsKey( city ) ) {

         // if city is in Map, and therefore in display
         // remove previous WeatherBean object
         WeatherBean previousWeather = 
            ( WeatherBean ) weatherItems.remove( city );
         weatherListModel.remove( previousWeather ); 
      }
      
      // add WeatherBean to Map and WeatherListModel
      weatherListModel.add( weather );
      weatherItems.put( city, weather );

   } // end method addItem

   // clear all cities from display
   public void clearCities()
   {
      weatherItems.clear();
      weatherListModel.clear();
   }
}

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