JEDI Course Notes-Mobile Application Devt-Lesson09-Optional Packages

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Optional Packages

1 Objectives

In this section, we will be delving into writing, building, using the emulator andpackaging J2ME applications. The Integrated Programming Environment that we will beusing is Netbeans (www.netbeans.org).

After finishing this lesson, the student should be able to:

know the functionalities provided by the Mobile Media API

play simple tones

play an audio file from the network and from the JAR

send and receive SMS messages

2 Overview

Not all devices are created equal and each device class comes with different features. Itwould be very difficult to create a standard specification that encompass all the existing

devices.

To accomodate the different capabilities of devices, MIDP has defined several optionalpackages. These packages are specific to and cater only to the specific device feature.

In this section, we will be discussing how to start using the Mobile Media API (MMAPI)and the Wireless Messaging API (WMA).

3 Mobile Media API (MMAPI)

The Mobile Media API (MMAPI) allows us to generate tones, play and record audio andvideo on compatible devices.

Playing or recording media is handled by two objects: the DataSource and the Player.

Mobile Application Development 1
http://www.netbeans.org/http://www.netbeans.org/


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The DataSource handles the details of getting the data from the source. The source maybe a file from the JAR or from the network (via HTTP), a record from the RMS, astreaming connection from a server or other proprietary source. The Player does nothave to worry about where the data came from or the manner in which it would befetched. All the Player has to do is to read the data from the DataSource, process and

display or playback the media to the output device.

A third actor in our scene is the Manager. The Manager creates players fromDataSources. The Manager has methods to create Players from media locators (URLlocations), DataSources and InputStreams.

You can query MMAPI properties via the String System.getProperty(String key).

Key Description

microedition.media.version The version of the MMAPI specificationimplemented by the device. Example: "1.1"

supports.mixing Returns "true" if the device supports audiomixing: can play at least two tonessimultaneously, can have at least twoPlayers playing audio simultaneously andcan play a tone even if at least one Playeris playing audio at the same time.


DataSource Player

DataSource Player

Manager


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Key Description

supports.audio.capture returns the String "true" if audio capture issupported. returns "false", otherwise.

supports.video.capture returns the String "true" if video capture issupported. returns "false", otherwise.

supports.recording returns "true" if recording is supported.

3.1 Tone generation

Playing a tone is as simple as calling the static method Manager.playTone(int tone, intduration, int volume). The valid values for the tone is from 0 to 127. The duration of theplaying of the tone is specified in milliseconds. The volume parameter is from 0 to 100.

import javax.microedition.midlet.*;

import javax.microedition.lcdui.*;

import javax.microedition.media.*;

import javax.microedition.media.control.*;

import java.io.*;

public class ToneMIDlet extends MIDlet implements CommandListener{

private Command exitCommand, playCommand;

private Form form;

private Gauge volumeGauge;

private Gauge durationGauge;

private Gauge toneGauge;

private Display display;

private int duration = 2; // seconds

private int volume = 100;

private int tone = ToneControl.C4;

private static int MAX_VOLUME = 100;

private static int MAX_TONE = 127;

private static int MAX_DURATION = 5;

public ToneMIDlet() {

playCommand = new Command("Play", Command.OK, 1);

exitCommand = new Command("Exit", Command.EXIT, 1);



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volumeGauge = new Gauge("Volume", true, MAX_VOLUME, volume);

toneGauge = new Gauge("Tone", true, MAX_TONE, tone);

durationGauge = new Gauge("Duration",true,MAX_DURATION,duration);

form = new Form("Tone Player");

form.addCommand(playCommand);

form.addCommand(exitCommand);

form.append(volumeGauge);

form.append(durationGauge);

form.append(toneGauge);

}

public void startApp() {

display = Display.getDisplay(this);

form.setCommandListener(this);

display.setCurrent(form);

}

public void pauseApp() {}

public void destroyApp(boolean unconditional) {}

public void commandAction(Command c, Displayable d) {

if (c == exitCommand) {

notifyDestroyed();

}

if (c == playCommand){

try {

volume = volumeGauge.getValue();

tone = toneGauge.getValue();

duration = durationGauge.getValue();

Manager.playTone(tone, duration*1000, volume);

} catch (MediaException mex){}

}

}

}



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3.2 Audio playback

The convenience method Manager.createPlayer(String URI) creates a player which willplay the data from the URI.





import java.io.*;

public class NetAudioMidlet extends MIDlet implements CommandListener{


private Form form;





Player player;

public NetAudioMidlet() {




form = new Form("Audio Player");




}







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try {

player = Manager.createPlayer(

"http://localhost:8084/Chapter07/bong.wav ");

player.realize();

// pre-fetch media to reduce latency

player.prefetch();

} catch (IOException ioex) {

display.setCurrent(new Alert("IO Exception",

ioex.getMessage(),null, AlertType.ERROR));

} catch (MediaException mex) {

display.setCurrent(new Alert("Media Exception",

mex.getMessage(),

null, AlertType.ERROR));

}

}





notifyDestroyed();

}


try {

VolumeControl control = (VolumeControl)

player.getControl("VolumeControl");

if (control != null){

control.setLevel(volumeGauge.getValue());

}

player.start();


http://localhost:8084/Chapter07/bong.wavhttp://localhost:8084/Chapter07/bong.wav


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mex.getMessage(), null, AlertType.ERROR));

} catch (Exception ex){

display.setCurrent(new Alert("Exception",

ex.getMessage(), null, AlertType.ERROR));

}

}

}

}

You can also play media from a file in the JAR by creating a Stream from the fileresource and passing it to Manager.createPlayer().





import java.io.*;

public class AudioMidlet extends MIDlet implements CommandListener{


private Form form;





Player player;

public AudioMidlet() {




form = new Form("Audio Player");




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}





}





notifyDestroyed();

}


try {

InputStream stream = getClass().

getResourceAsStream("bong.wav");

player = Manager.createPlayer(stream, "audio/x-wav");

player.realize();

VolumeControl control = (VolumeControl)

player.getControl("VolumeControl");

if (control != null){

control.setLevel(volumeGauge.getValue());

}

player.start();



mex.getMessage(), null, AlertType.ERROR));


display.setCurrent(new Alert("Exception",



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ex.getMessage(), null, AlertType.ERROR));

}

}

}

}

4 Wireless Messaging API (WMA)

4.1 Sending SMS

Using the Wireless Messaging API is very similar to connection via Sockets andDatagrams. In fact, it uses the same framework the Generic Connection Framework(GCF). The connection URL format to use is "sms://+639178888888", where"+639178888888" is the number of the phone you want to send messages to.

public void sendSMS(String number, String message) throws Exception{

String url = "sms://" + number;

MessageConnection connection =

(MessageConnection) Connector.open(url);

TextMessage msg = (TextMessage) connection.newMessage(MessageConnection.TEXT_MESSAGE);

msg.setPayloadText(message);

connection.send(msg);

connection.close();

}

Development of wireless applications on Netbeans 4.1 is very convenient. You don't haveto send actual SMS messages just to test your application. Netbeans (with mobility pack)

comes with J2ME Wireless Toolkit. This toolkit comes with an emulator. It also includestools for testing sending and receiving SMS messages. You can configure the phonenumber (address) of the emulated phone by opening the WMA preferences.

Tools

Java Platform Manager

J2ME Wireless Toolkit 2.2

Tools and Extensions

Open Preferences -> WMA



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Open Utilities -> WMA: Open Console



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import javax.microedition.io.*;

import javax.wireless.messaging.*;

public class SMSMidlet extends MIDlet implements CommandListener, Runnable{

private Command exitCommand, sendCommand;

private Form form;

private TextField addressField, mesgField;


public SMSMidlet() {

sendCommand = new Command("Send", Command.OK, 1);


addressField = new TextField(

"Phone Number", "+5550000", 32, TextField.ANY);

mesgField = new TextField(

"Message", "hello, world!", 160, TextField.ANY);

form = new Form("SMS Message");

form.append(addressField);

form.append(mesgField);

form.addCommand(sendCommand);


}





}





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notifyDestroyed();

}

if (c == sendCommand) {

Thread thread = new Thread( this );

thread.start();

}

}

/**

* Sends an SMS message to number. This method will throw an exception* if there is an error in connecting or sending the message.

* @param number

* @param message

*/

public void sendSMS(String number, String message) throws Exception{

String url = "sms://" + number;

MessageConnection connection =

(MessageConnection) Connector.open(url);

TextMessage msg = (TextMessage) connection.newMessage(

MessageConnection.TEXT_MESSAGE);

msg.setPayloadText(message);

connection.send(msg);

connection.close();

}

public void run() {

try {

String address = addressField.getString();

String message = mesgField.getString();

sendSMS(address, message);

display.setCurrent(new Alert("SMS Message",

"Message Sent\n"

+ "To: " + address + "\n"

+ "Message: " + message,

null, AlertType.INFO));



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} catch (Exception ex) {

display.setCurrent(new Alert("SMS Error", ex.getMessage(),

null, AlertType.ERROR));

}

}

}



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4.2 Receiving SMS

To receive a text message, open a MessageConnection specifying a port. The protocolstring for SMS messaging is "sms". This command will listen for incoming SMS messagesfrom port 8888:

conn = (MessageConnection) Connector.open("sms://:8888");

We must register our application to be a Message Listener so that the AMS will notify ourMIDlet of incoming messages.

conn.setMessageListener(this);

The notifyIncomingMessage will be called by the AMS once a message is received by the

device. We will need to create a separate Thread for reading messages so that theListener callback method can exit immediately.

public void notifyIncomingMessage(MessageConnection messageConnection) {

if (thread == null){

thread = new Thread(this);

thread.start();

}

}



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In our run() method, we are now ready to get the message:

public void run(){

try {

// wait for and receive message

Message mesg = conn.receive();

// Received a message

// Check if this is a text message (and not MMS, etc.)

if (mesg != null && mesg instanceof TextMessage) {

TextMessage text = (TextMessage) mesg;addressField.setText(text.getAddress());

mesgField.setText(text.getPayloadText());

dateField.setText("" + text.getTimestamp());

statusField.setText("Message received.");

}

} catch (Exception e) {

statusField.setText("Error: " + e.getMessage());

}

thread = null;

}

Here is the complete source code listing for our SMS Receiver:



import javax.microedition.io.*;

import javax.wireless.messaging.*;

public class SMSReceiverMidlet extends MIDlet

implements CommandListener, MessageListener, Runnable {

private Command exitCommand, sendCommand;

private Form form;

private StringItem statusField, addressField, mesgField, dateField;




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private MessageConnection conn;

private Thread thread;

private String port = "8888";

public SMSReceiverMidlet() {


statusField = new StringItem("Status:", "");

addressField = new StringItem("From:", "");

mesgField = new StringItem("Message:", "");

dateField = new StringItem("Timestamp:", "");

form = new Form("SMS Receiver");

form.append(statusField);

form.append(addressField);

form.append(mesgField);

form.append(dateField);


}




startReceiver();


}

public void pauseApp() {

thread = null;

}

public void destroyApp(boolean unconditional) {

thread = null;

if (conn != null){

try {

conn.close();

} catch (Exception ex){}



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}

}



notifyDestroyed();

}

}

private void startReceiver(){

try {

String addr = "sms://:" + port;if (conn == null){

conn = (MessageConnection) Connector.open(addr);

conn.setMessageListener(this);

statusField.setText(

"waiting for message at port " + port);

}


statusField.setText("Cannot open connection on port "

+ port + ":" + ex.getMessage());

}


thread.start();

}

public void notifyIncomingMessage(MessageConnection messageConn){

if (thread == null){


thread.start();

}

}

public void run(){

try {



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// wait for and receive message

Message mesg = conn.receive();

// Received a message

// Check if this is a text message (and not MMS, etc.)

if (mesg != null && mesg instanceof TextMessage) {

TextMessage text = (TextMessage) mesg;

addressField.setText(text.getAddress());

mesgField.setText(text.getPayloadText());

dateField.setText("" + text.getTimestamp());

statusField.setText("Message received.");

} else {statusField.setText(

"Non-text message received: "

+ mesg.getClass().toString());

}

} catch (Exception e) {

statusField.setText("Error: " + e.getMessage());

}

thread = null;

}

}



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5 Exercises

5.1 Audio Player

Create a MIDlet that will play an audio file for an idefinite number of times (loop). Theaudio file should be read from the JAR. Hint: you must set a property on the Player tocontrol the looping.

5.2 SMS Auto-Responder

Create a MIDlet that will automatically reply when it receives a text message. Hint: youcan modify the SMSReceiverMidlet and use the same connection to send the replymessage.


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JEDI Course Notes-Mobile Application Devt-Lesson09-Optional Packages