checkgaswindow.java

myMileage是一个简单地系统

import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import javax.swing.event.*;

import java.util.*;

public class CheckGasWindow extends JFrame implements ActionListener , WindowListener , KeyListener {

	private static CheckGasWindow instance = null;
	
	private final String CONTINUE = "Continue";
	
	private Color bgcolor = Color.WHITE;
	
	private double remainingGas;
	
	private JTextField gallonsInput= new JTextField( 10 );
	
	public static void getInstance() {
		if( instance == null ) instance = new CheckGasWindow();
	}
	
	protected CheckGasWindow() { super(); this.makeGUI(); }
	
	private void makeGUI() {
		setTitle( "Gas Level" );
		setSize( new Dimension( 200 , 180 ) );
		Mileage m = Mileage.getInstance();
		Point p = m.getLocation();
		int x = (int)p.getX();
		int y = (int)p.getY();
		setLocation( x + 100 , y + 100 );
		getContentPane().setBackground( bgcolor );
		getContentPane().setLayout( new GridLayout( 3 , 1 , 5 , 0 ) );
		Vector entries = Mileage.getInstance().getEntries();
		JPanel labelWrapper = new JPanel();
		labelWrapper.setBackground( bgcolor );
		labelWrapper.setLayout( new FlowLayout() );
		JPanel labels = new JPanel();
		labels.setBackground( bgcolor );
		labels.setLayout( new GridLayout( 3 , 1 , 5 , 0 ) );
		labels.add( new JLabel( "Approximately how much gas" ) );
		labels.add( new JLabel( "was in the vehicle after your" ) );
		labels.add( new JLabel( "fueling on " + ( (TableEntry)entries.get( entries.size() - 1 ) ).getDate() + "?" ) );
		labelWrapper.add( labels );
		getContentPane().add( labelWrapper );
		JPanel input = new JPanel();
		input.setBackground( bgcolor );
		input.setLayout( new FlowLayout() );
		gallonsInput.addKeyListener( this );
		input.add( gallonsInput );
		getContentPane().add( input );
		JPanel buttonPanel = new JPanel();
		buttonPanel.setBackground( bgcolor );
		buttonPanel.setLayout( new FlowLayout() );
		buttonPanel.add( makeButton( CONTINUE ) );
		getContentPane().add( buttonPanel );
		addWindowListener( this );
		addKeyListener( this );
		setVisible( true );
	}
	
	private JButton makeButton( String text ) {
		JButton button = new JButton( text );
		button.setActionCommand( text );
		button.setToolTipText( text );
		button.addActionListener( this );
		return button;
	}

	public void windowClosing( WindowEvent e ) {
		Vector entries = Mileage.getInstance().getEntries();
		
		instance = null;
		dispose();
	}
	
	public void windowActivated( WindowEvent e ) {}
	public void windowClosed( WindowEvent e ) {}
	public void windowDeactivated( WindowEvent e ) {}
	public void windowDeiconified( WindowEvent e ) {}
	public void windowIconified( WindowEvent e ) {}
	public void windowOpened( WindowEvent e ) {}
	
	
	public void actionPerformed( ActionEvent e ) {
		String command = e.getActionCommand();
		if( command.equals( CONTINUE ) ) {
			next();
		}
	}
	
	private void next() {
		double remainingGas = 0;
		String input = gallonsInput.getText();
		String errorMsg = "";
		boolean okToContinue = true;
		if( input.equals( "" ) ) {
			errorMsg = "Please fill in the text field.";
			okToContinue = false;
		} else {
			try {
				remainingGas = (new Double( input )).doubleValue();
				Vector entries = Mileage.getInstance().getEntries();
				double lastFill = (new Double( ( (TableEntry)entries.get( entries.size() - 1 ) ).getGallons() ) ).doubleValue();
				if( remainingGas < lastFill ) {
					errorMsg = "You pumped " + lastFill + " gallons last time, you must " +
								"\nhave had at least that much gas!";
					okToContinue = false;
				}
			} catch( NumberFormatException nf ) {
				errorMsg = "Please enter a valid numeric value.";
				okToContinue = false;
			}
		}
		
		if( okToContinue ) {
			ReportWindow.getInstance( remainingGas );
			windowClosing( null );
		} else {
			JOptionPane.showMessageDialog( null , errorMsg ,"Oops" , JOptionPane.WARNING_MESSAGE );
		}
	}
		

	public void keyReleased( KeyEvent e ) {
		if( e.getKeyCode() == KeyEvent.VK_ENTER )
			next();
	}
	public void keyTyped( KeyEvent e ) {}
	public void keyPressed( KeyEvent e ) {}
		
}