welcomepanel.java

汽车销售系统汽车销售系统汽车销售系统汽车销售系统汽车销售系统汽车销售系统

import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import javax.swing.event.*;
import javax.swing.border.*;
/**
 * A welcome dialog, which displays basic statistics about the cars in the data file
 * @
 *
 * PUBLIC FEATURES:
 * // Constructors
 *    public WelcomePanel(CarSalesSystem carSys, JPanel dest, String data)
 *
 * // Methods
 *    public void carsUpdated(CarUpdateEvent ev)
 *    public void stateChanged(ChangeEvent ev)
 *
 * COLLABORATORS:
 *
 *
 * @version 1.0, 16 Oct 2004
 * @author Adam Black
 */
public class WelcomePanel extends JPanel implements ChangeListener
{
	private CarSalesSystem carSystem;
	private JLabel headingLabel = new JLabel("Welcome to the Car Sales System", JLabel.CENTER);
	private JLabel carsLabel = new JLabel();
	private JLabel manufacturersLabel = new JLabel();
	private JLabel avgPriceLabel = new JLabel();
	private JLabel avgKmLabel = new JLabel();
	private JLabel avgAgeLabel = new JLabel();
	private JLabel versionLabel = new JLabel();
	private JLabel dataSizeLabel = new JLabel();
	private JPanel statsPanel = new JPanel();
	private JPanel centerPanel = new JPanel(new FlowLayout(FlowLayout.LEFT, 10, 5));
	private boolean carsUpdated = false;
	private String file;

	/**
	 * @param carSys link to CarSalesSystem object
	 * @param dest panel to place components within
	 * @param data filename of data file
	 */
	public WelcomePanel(CarSalesSystem carSys, String data)
	{
		carSystem = carSys;
		file = data;
		setLayout(new BorderLayout(0, 10));
		carSys.addCarUpdateListener(this);

		statsPanel.setLayout(new BoxLayout(statsPanel, BoxLayout.Y_AXIS));
		centerPanel.add(statsPanel);
		headingLabel.setBorder(new EmptyBorder(new Insets(10, 0, 0, 0)));

		updateStats();

		statsPanel.add(carsLabel);
		statsPanel.add(manufacturersLabel);
		statsPanel.add(avgPriceLabel);
		statsPanel.add(avgKmLabel);
		statsPanel.add(avgAgeLabel);
		statsPanel.add(Box.createVerticalStrut(20));
		statsPanel.add(versionLabel);
		statsPanel.add(dataSizeLabel);

		add(headingLabel, "North");
		add(centerPanel, "Center");
	}

	/**
	 * this method is invoked when a car has been added to the system.
	 *
	 * @param ev CarUpdateEvent Object
	 */
	public void carsUpdated(CarUpdateEvent ev)
	{
		if (ev.getSource() == carSystem)
		{
			carsUpdated = true;
		}
	}

	/**
	 * when the tab on the main frame gets changed over to this one, we may have to update the
	 * car list with the latest version
	 *
	 * @param ev ChangeEvent object
	 */
	public void stateChanged(ChangeEvent ev)
	{
		// the source came from a JTabbedPane
		if (ev.getSource() instanceof JTabbedPane)
		{
			JTabbedPane tab = (JTabbedPane)ev.getSource();
			// the Welcome tab has just been chosen
			if (tab.getSelectedIndex() == 0)
			{
				// if the statistics is not up to date
				if (carsUpdated)
				{
					// update them
					updateStats();
					// next time don't update the statistics, unless a car is added to the system
					carsUpdated = false;
				}
			}
		}
	}

	/**
	 * update all the statistics
	 */
	private void updateStats()
	{
		// receive new statistics
		int cars = (int)carSystem.getStatistics(CarSalesSystem.CARS_COUNT);
		int manufacturers = (int)carSystem.getStatistics(CarSalesSystem.MANUFACTURERS_COUNT);
		double avgPrice = Math.floor(carSystem.getStatistics(CarSalesSystem.AVERAGE_PRICE) * 10 + 0.5) / 10;
		double avgKm = Math.floor(carSystem.getStatistics(CarSalesSystem.AVERAGE_DISTANCE) * 10 + 0.5) / 10;
		double avgAge = Math.floor(carSystem.getStatistics(CarSalesSystem.AVERAGE_AGE) * 10 + 0.5) / 10;
		java.io.File f = new java.io.File(file);
		long size = f.length(); // get length of binary data file

		carsLabel.setText("Total number of cars: " + String.valueOf(cars));
		manufacturersLabel.setText("Total number of manufacturers: " + String.valueOf(manufacturers));
		avgPriceLabel.setText("Average car price: " + String.valueOf(avgPrice));
		avgKmLabel.setText("Average car kilometers: " + String.valueOf(avgKm));
		avgAgeLabel.setText("Average car age: " + String.valueOf(avgAge));
		versionLabel.setText("Car Sales System, Version " + CarSalesSystem.APP_VERSION);
		dataSizeLabel.setText("Size of data file: " + size + " bytes");
	}
}