CIS 642 - Mobile Information Device profie

Mobile

1. MIDP
Mobile Information
Device Profile
Johnny Yau
CIS 642
Prof. Insup Lee

2. Introduction
MIDP = Mobile Information Device
Profile
Spearheaded by Sun, Motorola, and
Nokia
Latest attempt by Sun to bring JAVA
into embedded systems, specifically
mobile phone

3. Motivation Behind MIDP
Heterogeneous development
platforms in mobile phone arena
Short product life cycles
MIDP attempts to solve that via
offering a standard environment for
application programmers

4. What is MIDP?
Set of JAVA APIs
Implements a MIDlet class
Addresses issues such as user
interface, persistent storage,
networking, and application model
Targeted towards mobile phones
Basically JAVA for mobile phones

5. Implementation
Stacked on top of Connected Limited
Device Configuration (CLDC) and
KVM

6. Implementation (cont)
Operates over existing network
protocols such as IrDA, Bluetooth,
IEEE 802.11, and wireless networks
Specifications are targeted towards
mobile phones
Other devices such as PDAs may find
more use in a super set of the MIDP
APIs

7. Service Model

8. Retrieval
Medium Verification
Figure out which communication device
to use (e.g. Bluetooth or IEEE 802.11)
Negotiations

9. Negotiations
Server and mobile device exchange
information about the MIDlet and
mobile device, respectively
Information such as device
capabilities (e.g. processing power,
volatile memory available), device
size, MIDlet requirements may be
exchanged

10. Negotiations (cont)
Crux of the useful capabilities
offered by MIDP
Especially important when it comes
to making things work over devices
with different sized screens and
different capabilities

11. Installation
Download
Security Verification
Check that the MIDlet does not violate
security issues
Transformation
Convert public representation to
internal representation

12. Launch
When selected by user application is
moved into KVM and run

13. Upgrade & Removal
Applications can be upgraded when
new versions become available
An application permanently stored
locally on device can be removed
from persistent storage when
selected for removal by user

14. Provided by Mobile Device
Classes and native code that
implements CLDC
JAVA Virtual Machine (KVM)
Native code for the MIDP

15. Provided by JVM & CLDC
Multi-threading
Locking
Synchronization
Execution of byte code
Method dispatching

16. MIDlet Class
All MIDP applications MUST inherit
from the MIDlet class
Does not have a main() function
Cannot call System.exit()
It triggers a SecurityException to be
thrown

17. JAVA Packages
java.lang.*
java.io.*
java.util.*
javax.microedition.io.*
javax.microedition.ui.*
javax.microedition.rms.*
javax.microedition.midlet.*

18. javax.microedition.io
StreamConnection
To open a basic connection that
reads/writes simple data.
ContentConnection
To open a connection that provides
content length, type, and encoding
information. This interface extends
from the StreamConnection interface.

19. javax.microedition.io
HttpConnection
To open a connection that provides
capabilities to interface through HTTP
including getting/setting headers and
HTTP-specific handling. This interface
extends from the
ContentConnectioninterface.

20. javax.microedition.ui
Offers two major choices in interface
design
Canvas
Used to construct a custom interface
using the Graphics object
Mainly used for multithreaded games or
non-traditional interfaces

21. javax.microedition.ui
Screen
For the construction of form based user
interfaces

22. javax.microedition.rms
Contains the classes needed to
implement a temporary storage
database on the device
Limited in capabilities because of the
restrictions imposed by mobile
phones

23. javax.microedition.midlet
MIDlet
Used to build MIDP applications

24. Hello World MIDlet
import javax.microedition.midlet.*;
import javax.microedition.lcdui.*;
public class HelloMidlet extends MIDlet implements CommandListener
{
    // Initialize the Midlet Display variable
    private Display midletDisplay;
    // Initialize a variable for the doneCommand
    private Command doneCommand;
    public HelloMidlet()
    {
      // Retrieve the display from the static display object
      midletDisplay = Display.getDisplay(this);
        // Initialize the doneCommand
      doneCommand = new Command("DONE", Command.SCREEN, 1);
    }

25.      /**
     * Create the Hello Midlet World TextBox and associate
     * the exit command and listener.
     */
    public void startApp()
    {
        // Create the TextBox containing the "Hello Midlet World!!" message
        TextBox textBox = new TextBox("Hello Midlet", "Hello Midlet World!!", 256, 0);
        // Add the done Command to the TextBox
        textBox.addCommand(doneCommand);
        // Set the command listener for the textbox to the current midlet
        textBox.setCommandListener( (CommandListener) this);
        // Set the current display of the midlet to the textBox screen
        midletDisplay.setCurrent(textBox);
    }
    /**
     * PauseApp is used to suspend background activities and release
     * resources on the device when the midlet is not active.
     */
    public void pauseApp()
    {
    }
   

26.  /**
     * DestroyApp is used to stop background activities and release
     * resources on the device when the midlet is at the end of its
     * life cycle.
     */
    public void destroyApp(boolean unconditional)
    {
    }
    /*
     * The commandAction method is implemented by this midlet to
     * satisfy the CommandListener interface and handle the done action.
     */
    public void commandAction(Command command, Displayable screen)
    {
      // If the command is the doneCommand
      if (command == doneCommand)
      {
            // Call the destroyApp method
            destroyApp(false);
            // Notify the midlet platform that the midlet has completed
            notifyDestroyed();
      }
    }
}

27. Screenshot

28. Development Cycle
Write application using MIDP APIs
Compile
Pre-verify
Pre-processes the class for use in KVM
Test
Package classes into a .jar file
Test with Package

29. Hits
Simpler development
Runs on acceptably well on
heterogeneous platforms

30. Misses
Too bloated really for mobile phones
Not powerful enough for devices like
PDAs and Wireless Internet
Appliances that have more resources
available
Though a superset of the APIs may
work fine