Problem in State Design Pattern

[Thamu Gurung]

Hi,

Really appreciate for all you help with my previous project. It was really nice and I got good grades in that . Thankyou everybody who gave their valuable time to me.

Now this time I have got some problems in making a automatic door locking system in State Design Pattern, I have searched internet but could not find any good examples of that .

My another problem is :

1) How to make an array of captured events.
2) how to synchronise the evetns .

Anyone could please help me understand the state desing pattern .

Regards ,

[Peter Taucher]

'Thinking in Java' should have the pattern discussed and also provide an example.

Our friend Google also gives some advice / directions:
http://www.javabeat.net/tips/5-state-pattern-design-patterns-in-javaj2ee.html
http://java-x.blogspot.com/2006/12/implementing-state-pattern-in-java.html
http://blogs.sun.com/jkumaran/entry/state_design_pattern_using_java

To your questions:
1) Why do you need an array (fixed size) for captured events? Wouldn't something like a Queue seem a natural approach?
2) TellTheDetails

[Thamu Gurung]

Hi Peter,

Thanks for the links.

Actually was trying to explore some more events in java , and got strucked in handling two or more button events at the same time.

In my simple design there are four button 1,2,3,4 and below is the textarea which is black in colour bydefault and , when any user cliks on 4 and then 3 , in seqeunce (first 4 , then 3), then the Color of the textarea , should be changed as green.

my code is here below:

import java.util.Vector;
import java.awt.*;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.*;


import javax.swing.*;
import javax.swing.JButton;
import javax.swing.JTextField;

public class ChangeColor extends JFrame implements ActionListener {
	private JPanel panel;
	private JButton b1,b2,b3,b4;
	final JTextField jt;

	public ChangeColor(String title) {

		super(title);

		Container c = getContentPane();
		c.setLayout(new BorderLayout());
			JPanel panel=new JPanel();
			panel.setLayout(new GridLayout(4, 1, 5, 5));
			b1=new JButton("1");
			b2=new JButton("2");
			b3=new JButton("3");
			b4=new JButton("4");



			panel.add(b1);
			panel.add(b2);
			panel.add(b3);
			panel.add(b4);

			b3.addActionListener(this);
			b4.addActionListener(this);








		JPanel panel1=new JPanel(new FlowLayout());
		 jt=new JTextField(2);
		jt.setBackground(Color.BLACK);
		panel1.add(jt);

		setSize(250,400);

		c.add(panel,BorderLayout.CENTER);
		c.add(panel1,BorderLayout.SOUTH);
		setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
		setVisible(true);
	}

							public void actionPerformed(ActionEvent e) {

									if((e.getSource()==b4)&&(e.getSource()==b3)){ // here having error , cant handle both at same time..
									      //if(e.getSource()==b4){ --- if doing for single button its working ..
										jt.setBackground(Color.GREEN);

								 	}
							}


		 public static void main(String[] args) {
		new ChangeColor("Simple Evetn Try");
	}
}

Much help be appreciated .


Many Thanks

[Peter Taucher]

Maybe something like a stack for remembering the event sequence?

public class ChangeColor
    extends JFrame
    implements ActionListener
{
    private final JPanel        panel;
    private final JButton       b1, b2, b3, b4;
    private final JTextField    jt;
    private final Stack<Object> evtStack;
    
    public ChangeColor( String title )
    {   
        super( title );
        
        evtStack = new Stack<Object>();
        
        Container c = getContentPane();
        c.setLayout( new BorderLayout() );
        panel = new JPanel();
        panel.setLayout( new GridLayout( 4, 1, 5, 5 ) );
        b1 = new JButton( "1" );
        b2 = new JButton( "2" );
        b3 = new JButton( "3" );
        b4 = new JButton( "4" );
        
        panel.add( b1 );
        panel.add( b2 );
        panel.add( b3 );
        panel.add( b4 );
        
        b1.addActionListener( this );
        b2.addActionListener( this );
        b3.addActionListener( this );
        b4.addActionListener( this );
        
        JPanel panel1 = new JPanel( new FlowLayout() );
        jt = new JTextField( 2 );
        jt.setBackground( Color.BLACK );
        panel1.add( jt );
        
        setSize( 250, 400 );
        
        c.add( panel, BorderLayout.CENTER );
        c.add( panel1, BorderLayout.SOUTH );
        setDefaultCloseOperation( JFrame.EXIT_ON_CLOSE );
        setVisible( true );
    }
    
    public void actionPerformed( ActionEvent e )
    {
        Object src = e.getSource();
        
        if ( src == b1 )
        {  
            jt.setBackground( Color.RED );
        }
        else if ( src == b2 )
        {  
            jt.setBackground( Color.GREEN );
        }
        else if ( src == b3 )
        {  
            // Peek at top of stack for latest event
            if ( evtStack.peek() == b4 )
            {
                jt.setBackground( Color.CYAN );
            }
            else
            {
                jt.setBackground( Color.PINK );
            }
            
            evtStack.clear();
        }
        else if ( src == b4 )
        {
            jt.setBackground( Color.BLUE );
        }
        
        // Remember all events in a queue
        evtStack.push( src );
    }
    
    public static void main( String[] args )
    {
        SwingUtilities.invokeLater( new Runnable()
        {   
            @Override
            public void run()
            {
                new ChangeColor( "Simple Evetn Try" );
            }
        });
    }
}

[Thamu Gurung]

Hi Peter,

Thanks for your kind reply.

It realy gave me idea of using Stacks , which i have never used .

Really appreicate your kind help.


Best Regards ,


Thamu