This document provides instructions for developing a simple "Hello World" mobile application called a midlet using Java ME. It explains the steps to create a new project in the Java ME SDK, selecting the MIDP 2.0 device profile. It also summarizes the key aspects of a midlet's lifecycle, including initialization in the constructor, becoming active in startApp(), and transitions between active and paused states.

1. Java Mobile Programming
Africa Nazarene University,
Meru Campus
May Trimester, 2013
Raphael Wanjiku,
Computer Science Department

2. Developing Midlets
Midlet- A java application that can run on any MIDP device.
We will develop our applications using the Sun’s J2ME Wireless Toolkit.
Hello world Midlet
Steps
1. Click on File ->New Project ->Categories(Java ME SDK) ->MIDP Application
2. Name the project as HelloApp and do not deselect the checkboxes.
3. Select Device(for Emulation)
4. Select device configuration as CLDC-1.0
5. Select Device profiles as MIDP-2.0 and click finish.
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3. 1. These imports the necessary classes required for use by the Midlet
2. Declaration of variables to be used in the Midlet
3. Creation of the constructor HelloMidlet().This is where objects are instantiated.
4. Instantiation of the different classes objects.
5. Implementation of the setCommandListener () method on the command object.
6. Setting of the displayable object upon call of the startApp().
7. Shows the class scope. This is shown by the curly braces.
8. Implementation of the commandAction().This is where one specifies which command
navigates where.
Midlet Lifecycle
A Midlet’s lifecycle is reflected in the methods and behaviour of the MIDlet class. A MIDlet
goes through the following states:
a) When a MIDlet is run, the constructor is run creating an instance. It is in the paused
state.
b) The MIDlet then enters the Active state when the startApp () is called.
c) While the MIDlet is still in the active state, its execution can be suspended entering
into paused state. This is effected by calling notifyPaused ().
d) While in the paused state, it can resume by calling startApp() to put it back into the
active state.
e) The MIDlet can be terminated by calling the destroyApp() or auto-destroy by calling
notifyDestroyed().
Code Explanation