Introduction to Java ME Mobile Development discussed by Prof. Erwin Globio from http://eglobiotraining.com/

1. Introduction to JAVA ME Mobile
Application Development
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Prof. Erwin M. Globio, MSIT
Resource Speaker
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JAVA Mobile Apps

2. Mobile Devices
Mobile devices may vary in size, design and layout, but they have
some characteristics in common that are totally different from desktop
systems.
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Small in size
Mobile devices are small in size. Consumers want smaller
devices for mobility and convenience.
Limited memory
Mobile devices also have small memory, both primary (RAM)
and secondary (disk). This limitation is one of the factors that
affects writing programs for these types of devices. With
limited amount of memory, special considerations must be
taken to conserve the use of this precious resource.
JAVA Mobile Apps

3. Continuation (Mobile Devices)
Limited processing power
Mobile systems are not as powerful as their desktop
counterparts. Size, technology and budget are some of the
factors that affect the state of this resource. Like the disk
storage and RAM, you can only fit so much of these resources
in such a small package.
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Low power consumption
Mobile devices consume less power than desktop machines.
These devices must conserve the use of power because they
run on a limited supply from batteries.
Robust and reliable
Because mobile devices are always carried along, they must
be robust enough to stand the force of bumps, motion and
occasional drops.
JAVA Mobile Apps

4. Continuation (Mobile Devices)
Limited connectivity
Mobile devices have low bandwidth, some of them not
connected at all. Most of them use wireless connections.
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Short wakeup time
These consumer devices startup in seconds and most of them
are always on. Take the case of mobile phones: they boot up
within seconds and most people do not turn them off even at
night. PDAs wakeup the second you press their power button.
JAVA Mobile Apps

5. Java Platform
Java was created in 1991 by James Gosling of Sun
Microsystems. Initially called Oak, in honor of the tree outside
Gosling's window, its name was changed to Java because there
was already a language called Oak.
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The original motivation for Java was the need for platform
independent language that could be embedded in various
consumer electronic products like toasters and refrigerators.
One of the first projects developed using Java was a personal
hand-held remote control named Star 7.
At about the same time, the World Wide Web and the Internet
were gaining popularity. Gosling realized that Java could be
used for Internet programming.
JAVA Mobile Apps

6. Continuation (Java Platform)
With the release of version 1.2, the Java platform was
classified into several editions: Now we have 1.7 version
JAVA SE – Java 2 Platform, Standard Edition
desktop applications
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JAVA EE – Java 2 Platform, Enterprise Edition
enterprise applications w/ focus on web server-side
development including servlets, JSP, EJB and XML
JAVA ME – Java 2 Platform, Micro Edition
mobile and handheld devices
JavaCard
Smart Cards
JAVA Mobile Apps

7. Continuation (Java Platform)
Servers
Servers
Desktop
machines
High-end
Optional consumer
Packages
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devices Low-end
consumer
Optional
Packages devices
Smart
Cards
J2EE Personal Profile
J2SE
Foundation Profile MIDP
Java
CDC CLDC
Card
Java Virtual Machine KVM Card VM
Java 2 Micro Edition (J2ME)
JAVA Mobile Apps

8. JAVA ME Overview
The Java Platform, Mobile Edition (JAVA ME) is a set
of specifications and technologies that focus on consumer
devices. These devices have limited amount of memory, less
processing power, small screens and low network bandwidth.
With the proliferation of mobile consumer devices
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from phones, PDAs, gaming boxes to home appliances, Java
provides a single portable environment for developing and
running applications on these devices.
JAVA ME programs, like all Java programs, are
interpreted. Programs are compiled into byte codes and
interpreted by the Java Virtual Machine (VM). JAVA ME
provides a consistent interface with the devices. Applications
do not have to be recompiled to be able to run on different
machines.
JAVA Mobile Apps

9. CLDC
The Connected Limited Device Configuration (CLDC) defines
and addresses the following areas:
Java language and Virtual Machine (VM) features
Core libraries (java.lang.*, java.util.*)
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Input/Output (java.io.*)
Security
Networking
Internationalization
JAVA Mobile Apps

10. MIDP
The Mobile Information Device Profile (MIDP) builds on top of the
CLDC.
The MIDP specification, much like the CLDC and other APIs, has
been defined through the Java Community Process (JCP). It
involved an expert group, from more that 50 companies,
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composed of mobile device manufacturers, carriers and software
developers.
MIDP defines the application model, user interface API, persistent
storage and networking, gaming and media API, security policies,
application deployment and over-the-air provisioning.
MIDlets
WMA MMAPI Optional OEM
MIDP 2.0
1.1 1.1 Packages APIs
CLDC 1.0 or 1.1
Device Operating System
JAVA Mobile Apps

11. MIDlet
An MIDP application is called a MIDlet. The device's application
management software (AMS) interacts directly with the MIDlet
with the MIDlet's create, start, pause, and destroy methods.
The MIDlet is part of the javax.microedition.midlet package. A
MIDlet must extend the MIDlet class. It can request
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parameters from the AMS as defined in the application
descriptor (JAD).
A MIDlet does not have (and MUST NOT have) a public static
void main(String[] argv) method. It will not be recognized by
the AMS as the program's starting point.
JAVA Mobile Apps

12. MIDlet Life Cycle
A MIDlet's life begins when it is instantiated by the AMS. It
initially enters the "Paused" state after being created with the
new command. The AMS calls the public no argument
constructor of the MIDlet. If an exception occurs at the
constructor, the MIDlet is put into a Destroyed state and
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discarded immediately.The MIDlet enters the Active state
upon calling the startUp() method by the AMS.
The MIDlet enters the Destroyed state when the AMS calls the
destroyApp() method. This state is also entered when the
notifyDestroyed() method returns succesfully to the
application. Take note that the MIDlet enters the Destroyed
state only once in its lifetime.
JAVA Mobile Apps

13. MIDlet Life Cycle
new
destroyApp()
startApp() Paused
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Destroyed
Active pauseApp()
destroyApp()
To be able to create a MIDlet, we must create a subclass of the
MIDlet class from javax.microedition.midlet package. We must
also override or implement the methods: startApp(),
destroyApp() and pauseApp(). These are the methods
expected by the AMS for running and controlling our MIDlet.
JAVA Mobile Apps

14. Using the Sun Wireless Toolkit
We'll now use the Sun Wireless Toolkit to compile and package our MIDlet
suite (containing a single MIDlet).
Open ktoolbar (from the Wireless Toolkit distribution)
Create a new project
Project Name: HelloMidlet
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MIDlet Class Name: HelloMidlet
On this Settings window, you can customize the a very comprehensive
selection of settings for your project. You can select what configuration to
use, what packages/APIs to include, Push Registry settings and more. For our
purposes, we will use the default project settings. Click "OK" to finish
creating the project.
Copy HelloMidlet.java into the project's "src directory: In Window, this is
under the directory: C:WTK23appsHelloMidletsrc (where C:WTK23 is
where you installed the wireless toolkit). Click "Build" and "Run":
JAVA Mobile Apps

15. Sample Code HelloMidlet
import javax.microedition.midlet.*;
import javax.microedition.lcdui.*;
public class HelloMidlet extends MIDlet implements CommandListener
{
Display display;
Command exitCommand = new Command("Exit", Command.EXIT, 1);
Alert helloAlert;
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public HelloMidlet(){
helloAlert = new Alert("Hello MIDlet", "Hello,
world!",null, AlertType.INFO);
helloAlert.setTimeout(Alert.FOREVER);
helloAlert.addCommand(exitCommand);
helloAlert.setCommandListener(this);
}
public void startApp() {
if (display == null){
display = Display.getDisplay(this);
}
display.setCurrent(helloAlert);
}
JAVA Mobile Apps

16. Sample Code HelloMidlet
public void pauseApp() { }
public void destroyApp(boolean unconditional) { }
public void commandAction(Command c, Displayable d){
if (c == exitCommand){
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destroyApp(true);
notifyDestroyed(); // Exit
}
}
}
JAVA Mobile Apps

17. Sample Code Explanation
Package javax.microedition.midlet
The MIDlet package defines Mobile Information Device Profile
applications and the interactions between the application and the
environment in which the application runs.
Package javax.microedition.lcdui
The UI API provides a set of features for implementation of user
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interfaces for MIDP applications.
public interface CommandListener
This interface is used by applications which need to receive high-
level events from the implementation. An application will provide an
implementation of a CommandListener (typically by using a nested
class or an inner class) and will then provide the instance to the
addCommand method on a Displayable in order to receive high-
level events on that screen.
JAVA Mobile Apps

18. Sample Code Explanation
Class Summary
Alert
An alert is a screen that shows data to the user and waits for a
certain period of time before proceeding to the next Displayable.
AlertType
The AlertType provides an indication of the nature of alerts.
ChoiceGroup
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A ChoiceGroup is a group of selectable elements intended to be
placed within a Form.
Command
The Command class is a construct that encapsulates the semantic
information of an action.
DateField
A DateField is an editable component for presenting date and time
(calendar) information that may be placed into a Form.
Display
Display represents the manager of the display and input devices of
the system.
JAVA Mobile Apps

19. Sample Code Explanation
Class Summary
Displayable
An object that has the capability of being placed on the display.
Implements a graphical display, such as a bar graph, of an integer
value.
List
A Screen containing list of choices.
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StringItem
An item that can contain a string.
TextBox
The TextBox class is a Screen that allows the user to enter and edit
text.
TextField
A TextField is an editable text component that may be placed into a
Form.
Ticker
Implements a "ticker-tape", a piece of text that runs continuously
across the display.
JAVA Mobile Apps

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SAMPLE PROGRAMS

21. PROFESSOR’S INFORMATION
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Prof. Erwin M. Globio, MSIT
Senior IT Lecturer of Far Eastern University
Owner and Senior Technical Trainer at http://eglobiotraining.com/
Email Address: erwin_globio@yahoo.com
Skype Id: erwinglobio

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