Learn with me

The BlueJ Discuss forum

2009-01-14T03:41:00.000-08:00

I ask many question on that milis(mailing list)

I try to ask some question on the BlueJ discuss.

The question is, How to connect using the real Mobile phones..
So my later script is REALY working :)
http://groups.google.com/group/bluej-discuss?hl=en

Server act

2008-12-31T03:13:00.000-08:00

when server receive the datagram..


public void run() {
..
....
        DatagramConnection dc = (DatagramConnection) Connector.open("datagram://:" + portString);
        f.insert(1,new StringItem("Server ready on port "+portString,""));
        sender = new Sender(dc);
        while (true) {
        Datagram dg = dc.newDatagram(100);
        dc.receive(dg);
        address = dg.getAddress();
        f.insert(1,new StringItem(address+" : ",new String(dg.getData(), 0, dg.getLength())));
        }
    }

The dialog, ...:

Server : waiting in the front house (near street)
Server : I'm ready at here !
Server : (making sender)
Server : prepare for receiving my goods(making a box, 10 x 2 x 5)
Server : waiting until I receiving my goods
Server : I get the goods! I'll put in the box.
Server : (See the sender label) aaah, from my client!
Server : (Placing the goods)I opened the box, and place the data in the "f" table.

The receive method at DatagramConnection class

2008-12-31T00:52:00.000-08:00

This important !
I think in the while(){} loop at the Server class, The Server is always receiving a blank datagram. But when i see in the Java Tutorial.

"The receive method waits forever until a packet is received. If no packet is received, the server makes no further progress and just waits. "

Connection ? : Datagram

2008-12-29T07:50:00.001-08:00

I'm always been very interested in connection in mobile phone, because phone comes handy, most of all my friend have phone and still connected. Now i want to LEARN connection, a Datagram connection. Datagram connection is simpler than Socket, that's what Java Tutorial said.

So.. let's begin.
First, I copied all of class in the WTK2.5.2_01 (C:\WTK2.5.2_01\apps\NetworkDemo\classes\datagram) to BlueJ! (The Readme.txt file also :D )
Compile all, deploy.

As seen in the readme file, "Run two instances of the emulator", "One acts as the datagram server, and the other as the datagram client". So, i click the Deploy button twice, and i get two emulator. After that, i go to the first emulator, and set that as server, and then set the client. I try to send a message to server, and in the server phone, i get the message. And then i try the other way. It Work !

That is the basic connection, i gonna edit them all.

updated!
The first thing that I do is, give the Server a Name !
So, in the Server class, I declare new variable called ServerName, and add new Constructor. Also a method that return the server name.
The variable


..
....

    private DatagramMIDlet parent;
    private Display display;
    private String serverName;   /**here*/
    private Form f;
    private StringItem si;
    private TextField tf;
..
..

the new Constructor


..
...
display.setCurrent(f);
    }
    
    public Server(DatagramMIDlet m, int p, String name) {
    parent = m;
    port = p;
    serverName = name;
    display = Display.getDisplay(parent);
    f = new Form(name);
    si = new StringItem("Status:", " ");
    tf = new TextField("Send:", "", 30, TextField.ANY);
    f.append(si);
    f.append(tf);
    f.addCommand(sendCommand);
    f.addCommand(exitCommand);
    f.setCommandListener(this);
    display.setCurrent(f);
    }
...
..

And.. getServerName() method,


public String getServerName()
    {
        return serverName;    
    }

I also edited the DatagramMIDlet class, so the server implementing my constructor(look at the commandAction method)


if (name.equals(SERVER)) {
  Server server = new Server(this, port,"The Server !");
  server.start();
     } else {
  Client client = new Client(this, port);
  client.start();
     }

Compile, Deploy, try becoming the Server, see what i have been changed ? :)

updated!
I have been edited many code of the server and client class
because of to much, i copy paste it directly

first, the server class


import java.io.*;
import javax.microedition.io.*;
import javax.microedition.lcdui.*;

public class Server implements Runnable, CommandListener {

    private DatagramMIDlet parent;
    private Display display;
    private String serverName;
    private Form f;
    private TextField tf;
    private Command sendCommand = new Command("Send", Command.ITEM, 1);
    private Command exitCommand = new Command("Exit", Command.EXIT, 1);
    Sender sender;
    private String address;
    private int port;

    ..
......
...
    
    public Server(DatagramMIDlet m, int p, String name) {
    parent = m;
    port = p;
    serverName = name;
    display = Display.getDisplay(parent);
    f = new Form(name);
    tf = new TextField("Send:", "", 30, TextField.ANY);
    f.append(tf);
    f.addCommand(sendCommand);
    f.addCommand(exitCommand);
    f.setCommandListener(this);
    display.setCurrent(f);
    }

    ....
.......
....

    public void run() {
    String portString = String.valueOf(port);
    try {
        f.insert(1,new StringItem("Waiting for connection on port"+portString,""));/**here*/
        DatagramConnection dc = (DatagramConnection) Connector.open("datagram://:" + portString); 

        sender = new Sender(dc);

        while (true) {
        Datagram dg = dc.newDatagram(100);
        dc.receive(dg);
        address = dg.getAddress();
        f.insert(1,new StringItem(address+" : ",new String(dg.getData(), 0, dg.getLength())));/**here*/
        }
    } catch (IOException ioe) {
        Alert a = new Alert("Server", "Port " + portString
            + " is already taken.", null, AlertType.ERROR);
        a.setTimeout(Alert.FOREVER);
        a.setCommandListener(this);
        display.setCurrent(a);
    } catch (Exception e) {
        e.printStackTrace();
    }
    }

    public void commandAction(Command c, Displayable s) {
    if ((c == sendCommand) && !parent.isPaused()) {
        if (address == null) {
        f.insert(3,new StringItem("Ooops! ","No destination address")); /**here*/
        } else {
        sender.send(address, tf.getString()); /**here*/
        f.insert(1,new StringItem("Me(Server) : ",tf.getString()));/**here*/
        tf.setString("");/**here*/
        }
    }

    public String getServerName()
    {
        return serverName;    
    }
    
    public String[] breakString(String s)
    {
        char[] ca = s.toCharArray();
        String[] sa = {};
        int h = 0;
        
        for(int w = 0;w <= ca.length-1;w++)
        {
            if(ca.equals(" "))
            {
                h = h + 1;
            }
            else
            {
                sa[h] = sa[h]+ca[w];
            }
        }
        return sa;
    }
    
}

The Client class


import java.io.IOException;

import javax.microedition.io.*;
import javax.microedition.lcdui.*;


public class Client implements Runnable, CommandListener {
    private DatagramMIDlet parent;
    private int port;
    private String ip; /**here*/
    private Display display;
    private Form f;
    private TextField tf;

    private Command sendCommand = new Command("Send", Command.ITEM, 1);
    private Command exitCommand = new Command("Exit", Command.EXIT, 1);

    Sender sender;

..
...
...
    
    public Client(DatagramMIDlet m, int p, String IP) {
    parent = m;
    port = p;
    this.ip = IP;  /**here*/
    display = Display.getDisplay(parent);
    f = new Form("Datagram Client");
    tf = new TextField("Send:", "", 30, TextField.ANY);
    f.append(tf);
    f.addCommand(sendCommand);
    f.addCommand(exitCommand);
    f.setCommandListener(this);
    display.setCurrent(f);
    }
..
...
...
    public void run() {
    String portString = String.valueOf(port);
    try {
        DatagramConnection dc = (DatagramConnection) Connector.open("datagram://"+ip+":" + portString); /**here*/

        f.insert(1,new StringItem("Waiting for connection "+ip+" on port "+portString,""));/**here*/

        sender = new Sender(dc);

        while (true) {
        Datagram dg = dc.newDatagram(100);
        dc.receive(dg);

        // Have we actually received something or
        // is this just a timeout ?
        if (dg.getLength() > 0) {
            f.insert(1,new StringItem("Server : ",new String(dg.getData(), 0, dg.getLength()))); /**here*/
        }
        }
    } catch (ConnectionNotFoundException cnfe) {
        ....
.....
..
    public void commandAction(Command c, Displayable s) {
    if ((c == sendCommand) && !parent.isPaused()) {
        sender.send(null, tf.getString());
        f.insert(1,new StringItem("Me(Client) : ",tf.getString()));/**here*/
        tf.setString("");/**here*/
    }

    if (c == exitCommand) {
        parent.destroyApp(true);
        parent.notifyDestroyed();
    }
    }

    public void stop() {
    }
    
}

And the DatagramMIDlet class


import javax.microedition.lcdui.*;
import javax.microedition.midlet.MIDlet;

public class DatagramMIDlet extends MIDlet implements CommandListener {

    private static final int DEFAULT_PORT = 5555;
    private String IP_ADDRESS;
    private static final String DEFAULT_IP = "202.3.213.129";
    private static final String SERVER = "Server";
    private static final String CLIENT = "Client";
    private static final String[] names = { SERVER, CLIENT };
    private static Display display;
    private Form f;
    private ChoiceGroup cg;
    private TextField portField;
    private TextField ipField; /**here*/
    private boolean isPaused;
    private Command exitCommand = new Command("Exit", Command.EXIT, 1);
    private Command startCommand = new Command("Start", Command.ITEM, 1);

    public DatagramMIDlet() {
    display = Display.getDisplay(this);
    f = new Form("Datagram Demo");
    cg = new ChoiceGroup("Please select peer", Choice.EXCLUSIVE, names,null);
    f.append(cg);
    portField = new TextField("Port number:", String.valueOf(DEFAULT_PORT),6, TextField.NUMERIC);
    ipField = new TextField("IP address:", DEFAULT_IP,20, TextField.ANY);/**here*/
    f.append(ipField);/**here*/
    f.append(portField);

    ....
........
......

    public void commandAction(Command c, Displayable s) {
    if (c == exitCommand) {
        destroyApp(true);
        notifyDestroyed();
    } else if (c == startCommand) {
        String name = cg.getString(cg.getSelectedIndex());
        int port = Integer.parseInt(portField.getString());
        String ip = ipField.getString(); /**here*/
        
        if (name.equals(SERVER)) {
        Server server = new Server(this, port,"The Server");/**here*/
        server.start();
        } else {
        Client client = new Client(this, port, ip);
        client.start();
        }
    }
    }
}

Playing with Graphics

2008-12-27T06:31:00.000-08:00

Now, i want to make an application that draw a line, and i have to matter with MIDlet image class, and MIDlet Graphics. So here it is.


...
public class DrawLine extends MIDlet implements CommandListener
{

    Form screen;
    Image line;
    TextField input_length;
    Graphics gr;

   /**
    * Called by the Application Management Software (AMS) when the MIDlet
    * begins execution.  The AMS is the software on a device that manages 
    * the downloading and life-cycle of MIDlets.  When this constructor 
    * returns, the AMS places the MIDlet in the Paused state.
    */
    public DrawLine()
    {
       screen = new Form("Draw.. Line...");      
       line = Image.createImage(screen.getWidth(),50);
       gr = line.getGraphics();
       input_length = new TextField("Input Length Here","",10,TextField.NUMERIC);
       screen.append(input_length);
       screen.append(line);
       screen.addCommand(new Command("Draw", Command.OK, 0));
       screen.addCommand(new Command("Exit", Command.EXIT, 0));
       screen.setCommandListener(this);
    }
...
..
    public void startApp()
    {
        Display.getDisplay(this).setCurrent(screen);
    }
..
..
public void commandAction(Command c, Displayable d)
    {
         
           if(c.getLabel().equals("Exit"))
           {
                notifyDestroyed();    
           }
           else if(c.getLabel().equals("Draw"))
           {
               Graphics g = line.getGraphics();
               int length = Integer.parseInt(input_length.getString());
               screen.delete(1);
               g.setColor(255,255,255);
               g.drawLine(0,20,g.getClipWidth(),20); // delete previouse image with white color ^_^"
               g.setColor(0,0,0);
               g.drawLine(0,20,length,20);
               input_length.setString("");
               screen.append(line);
            }

    }
}

Compile, Deploy, just input the length to the text box, and then click draw, it should draw a line with your input length in pixels.
After succeed with that, i want to make improvements. I crated a new class called DrawRectangle. I just add a new input field (TextField) because it's a rectangle who have width and height.


import javax.microedition.midlet.MIDlet;
import javax.microedition.lcdui.*;

/**
 * Class DrawRectangle - a simple MIDlet application that create rectangle image with user input
 *
 * @author     Keenan M
 * @version    1.0 :P
 */

public class DrawRectangle extends MIDlet implements CommandListener
{

    Form screen;
    Image rectangle;
    TextField input_width;
    TextField input_height;
    Graphics gr;

    public DrawRectangle()
    {
       screen = new Form("Draw.. Rectangle...");      
       rectangle = Image.createImage(screen.getWidth(),screen.getHeight());
       gr = rectangle.getGraphics();
       input_width = new TextField("Input Length Here","",10,TextField.NUMERIC);
       input_height = new TextField("Input Length Here","",10,TextField.NUMERIC);
       screen.append(input_width);
       screen.append(input_height);
       screen.append(rectangle);
       screen.addCommand(new Command("Draw", Command.OK, 0));
       screen.addCommand(new Command("Exit", Command.EXIT, 0));
       screen.setCommandListener(this);
    }

    public void startApp()
    {
        Display.getDisplay(this).setCurrent(screen);
    }

    public void pauseApp()
    {
    }

    public void destroyApp(boolean unconditional)
    {
    }
    
    public void commandAction(Command c, Displayable d)
    {
         
           if(c.getLabel().equals("Exit"))
           {
                notifyDestroyed();    
           }
           else if(c.getLabel().equals("Draw"))
           {
               Graphics gr = rectangle.getGraphics();
               int width = Integer.parseInt(input_width.getString());
               int height = Integer.parseInt(input_height.getString());
               screen.delete(2);
               /**              it's a clearing time */
               gr.setColor(255,255,255);
               gr.fillRect(1,1,screen.getWidth(),screen.getHeight());
               /**              end of clearing */ 
               gr.setColor(0,0,0);
               gr.drawRect(1,1,width,height);
               input_width.setString("");
               input_height.setString("");
               screen.append(rectangle);
            }
    }
}

Compile, Deploy, it's work, that code make me draw a rectangle :D.

updated!
Hmm, I think I should rename my Application to Drawer. woke, it's done.
Now, i want to make an application that make a String Image. with method drawString() in the graphics class. there it is.


import javax.microedition.midlet.MIDlet;
import javax.microedition.lcdui.*;

/**
 * Class DrawString - Draw string image
 *
 * @author     Keenan
 * @version    1.0
 */
public class DrawString extends MIDlet implements CommandListener
{

    Form screen;
    Image st;
    TextField input;
    Graphics gr;

    public DrawString()
    {
       screen = new Form("Draw.. String...");      
       st = Image.createImage(screen.getWidth(),15); // << string
       gr = st.getGraphics();
       input = new TextField("Input Here","",6+1+6+1+4,TextField.ANY);
       screen.append(input);
       screen.addCommand(new Command("Draw", Command.OK, 0));
       screen.addCommand(new Command("Exit", Command.EXIT, 1));
       screen.setCommandListener(this);
    }

    public void startApp()
    {
        Display.getDisplay(this).setCurrent(screen);
    }

    public void pauseApp()
    {
    }

    public void destroyApp(boolean unconditional)
    {
    }
    
    public void commandAction(Command c, Displayable d)
    {
        if(c.getLabel().equals("Exit"))
           {
                notifyDestroyed();    
           }
           else if(c.getLabel().equals("Draw"))
           {
               Graphics g = st.getGraphics();
               String v = input.getString();
               //screen.delete(1); << so it's like log message 
               g.setColor(255,255,255);
               g.fillRect(0,0,st.getWidth(),st.getHeight());
               g.setColor(0,0,0);
               g.drawString(v, 2,0,Graphics.LEFT|Graphics.TOP);
               input.setString("");
               screen.append(st);
            }   
    }
    
}

Compilelalalala, Deploylalala, it works! :D

Making a Simple Calculator

2008-12-27T06:29:00.000-08:00

I want to make a Calculator !


...
....
public class MyCalculator extends MIDlet implements CommandListener
{
...
....

After that, I preparing for the Item that i want to display in the screen
The item is :
3 TextField for inputing first value, second value, and the result.
1 ChoiceGroup for selecting the operator.
2 Command, one for exit, one for Calc(ulating) :D.
So..


..
...
private TextField fv = new TextField("First Value", "", 10, TextField.NUMERIC);
   private TextField sv = new TextField("Second Value", "", 10, TextField.NUMERIC);
   private TextField r = new TextField("Result", "", 50, TextField.ANY);
   String cgOperator[] = {"Divide","Times","Add","Subtract"};
   private ChoiceGroup operator = new ChoiceGroup("Operator",ChoiceGroup.EXCLUSIVE, cgOperator, null);
.....
.....

And of course, the commandAction() method..


...
..
public void commandAction(Command c, Displayable d) {
        // If it's our exitCommand, destroy ourselves
        if(c.getLabel().equals("Exit")) {
            notifyDestroyed();
        }else if(c.getLabel().equals("Calc")) {
            int first_value = Integer.parseInt(fv.getString());
            int second_value = Integer.parseInt(sv.getString());
            double result = 0;
            if(operator.isSelected(0))
            {
                result = first_value / second_value;
            }else if(operator.isSelected(1))
            {
                result = first_value * second_value;
            }else if(operator.isSelected(2))
            {
                result = first_value + second_value;
            }else if(operator.isSelected(3))
            {
                result = first_value - second_value;
                
            }
            r.setString(""+result+""); // <<< (i can't parseDouble() it.. :D)
        }
    }
...
..

Compile it, Deploy it, and I get my MIDlet Calculator !!! yeah

Spam blog ?

2008-12-27T05:19:00.000-08:00

aaah, my blog is marked by spam by the blogger
maybe that because i updated the blog by the existing post, not create a new blog
haha

Beginning of all : Making Mobile Application with BlueJ !

2008-12-25T19:28:00.000-08:00

Hello, my name is Keenan, and i want to learn how to make mobile application. In internet, i always find a great tutorials, great resource, and many more. I do love free, my teacher is internet. For now, I cant making any good mobile application using Java with BlueJ. I want too learn how to make good mobile applications ! I made this blog for posting my progress/improvement of making good mobile application !

So lets get started. You need JRE, download here.
I'm using BlueJ for this. You can download BlueJ here.
You need Wireless Toolkit 2.5.2 too ! download here.
That's it, i think that's is what i need.

I'm ready! did you ?

Okay, my first step, is searching in the bluej website for j2me. I got it here. After done reading that page and try they "command". I now can make simple application.

Now, time to edit the source code, of the Hello MIDlet that I downloaded. After seeking from the javax.microedition.lcdui API (you can see it at WTK 2.5.2 folder(C:\WTK2.5.2_01\docs\api\midp\index.html)). I found an Alert class, maybe i can use it. So, I edited the source code so like this !


import javax.microedition.midlet.*;
import javax.microedition.lcdui.*;

/**
* Class Hello - A simple Hello World MIDlet
*
* @author     Ian Utting
* @version    1.0
*/
public class Hello extends MIDlet implements CommandListener
{
   private Form screen;
   private Alert dor = new Alert("DOR !");/** HERE !*/
   private int a; /**HERE !!!*/

   public Hello()
   {
       screen = new Form("Hello Midlet");
       dor.setTimeout(1500); /**HERE !!!*/
       dor.setString(a + " Times..");  /**HERE !!!*/
       screen.append("Hello small world!");
       screen.addCommand(new Command("Exit", Command.EXIT, 0));
       screen.setCommandListener(this);
   }
   ..............
   .......

Hmm, I think to make application, that every time we click button, the alert will show, and print out many times we click that button ! for that, i make a variable called 'a'. And after that...


...
....
   public void commandAction(Command c, Displayable d) {
       // If it's our exitCommand, destroy ourselves
       if(c.getLabel().equals("Exit")) {
           notifyDestroyed();
       }
       if(c.getLabel().equals("Dor")) {    /**I add this !!!*/
           Display.getDisplay(this).setCurrent(dor);
           a += 1;
           dor.setString( a + " Times..");
       }
   }

I compile that, and then deploy. It's Work.

Now, i want display the clicked times in the form. I think, I will use text field.
I add this to the code


...
.....
public class Hello extends MIDlet implements CommandListener
{
   private Form screen;
   private TextField tf; /**HERE !!*/
   private int a = 0;
...
...

and then, in the Hello constructor


...
.....
   public Hello()
   {
       screen = new Form("Hello Midlet");
       tf = new TextField("hehe..","Hello small world!",255,TextField.ANY);
       screen.append(tf);
       screen.addCommand(new Command("Exit", Command.EXIT, 0));
       screen.addCommand(new Command("Dor", Command.ITEM, 0));
       screen.setCommandListener(this);
   }
...
..

After that, in the command listener.


public void commandAction(Command c, Displayable d) {
       // If it's our exitCommand, destroy ourselves
       if(c.getLabel().equals("Exit")) {
           notifyDestroyed();
       }
       if(c.getLabel().equals("Dor")) {
           a += 1;
       tf.setString("Hello small world!"+" \n "+ a +" Times :)");
       }
   }

Compile, Deploy, It's Work ! :D