APIs in J2ME

General APIs
The core APIs are defined by the underlying Connected Limited Device Configuration.

javax.microedition.io

Contains the Java ME-specific classes used for I/O operations.

javax.microedition.lcdui

Contains the Java ME-specific classes used for the GUI. LCDUI has a simple screen based approach where a single Displayable is always active at a time in the application user interface. LCDUI API provides a small set of displayables common in mobile device user interfaces: List, Alert, TextBox, Form and Canvas. For all displayables the device MIDP implementation has control over the presentation and layout of the displayable. Canvas is a low-level graphics surface for which an application has full control over what is rendered to it, although normally some space is reserved for system areas like screen title and indicators common in mobile device UIs. Since MIDP 2.0, Canvas also supports a full-screen mode that allows to make full screen graphics, which is especially useful for games.
LCDUI also has quite unique approach of abstract operations, called Commands. The placement of commands added to a displayable is completely up to the device implementation of this toolkit. The application programmer uses API specified command types to indicate the usage or purpose of the command in application user interface. Common types are BACK, EXIT, ITEM, SCREEN. The idea of the command abstraction is to make applications more portable between various different mobile device. Application developers should use the command types properly to indicate the purpose of an operation, and device implementation then places the operation to the common location for a given type in device's specific user interface style. This may be e.g. a specific key, like "a back navigation key" for BACK commands or button on screen.
The term LCDUI was actually a joke in JCP Expert Group that created it. It has not been opened up in the MIDP specifications but stands for Limited Capability Device User Interface. The joke was that no-one else really knows what it stands for. Then later the Programming Wireless Devices with the Java 2 Platform, Micro Edition book gave this term out.
Other common definitions have appeared. "Liquid Crystal Display User Interface" would reflect the fact that mobile phones normally use LCD displays; however, the API is not specifically tailored to this particular display technology. It is also said that "LCD UI" stands for "lowest common denominator" due to the fact the specific UI has simplest possible design.

javax.microedition.rms

Provides a form of persistent storage for Java ME. It's like a database for the mobile device.
"Record Store"(class) is used to store the Data: RecordEnumeration(Interface) , RecordComparator(Interface), RecordFilter(Interface), are used to apply user queries for sorting,filtering the data of all the data present; and comparison of contents of two or more RecordStores is done by these Interfaces.Data is stored and must be retrieved from the RecordStore using a ByteArray.(i.e; data is stored in Bytes(string.getBytes() and stored in ByteArray Byte a[])

javax.microedition.midlet

Contains the base classes for Java ME applications.

Specialized APIs added in MIDP 2.0

MIDP 2.0 saw the introduction of gaming and multimedia APIs and some optional packages.

javax.microedition.media

Contains the base classes of the multimedia playback. These are approximately a subset of the JSR 135 Java Mobile Media API.

javax.microedition.lcdui.game

A gaming API aimed at simple 2D sprite based games.

javax.microedition.pki

Authenticate APIs for secure connections.

Optional JSRs

The following JSRs are not part of MIDP (1.0 or 2.0) but provide extra functionalities on some handsets. However, there is no guarantee that a MIDP2.0 handset implement such APIs

javax.microedition.messaging

Wireless messaging API (optional), for sending SMS and MMS messages.

javax.microedition.pim

Personal information management API (optional), access the device's Address Book , to-do List, Calendar.

javax.microedition.io.file

The File Connection Optional Package (FCOP) is one of two optional packages defined by JSR 75 through the Java Community Process. The FileConnection API specified in JSR 75 gives access to the local file systems on devices like PDA. In order to overcome security issues MIDlet needs to include requested file permission in its JAD file under MIDLet-Permission property.

Development Tools

There are several different ways to create MIDP applications: Code can be written in a plain text editor, or you can use a more advanced IDE such as NetBeans, IntelliJ (with bundled Java ME plugin), or Eclipse (with plugins such as EclipseME) which has a user interface for graphically laying out any forms you create, as well as providing many other advanced features not available in a simple text editor.

Noteworthy Limitations of MIDP 1.0

• MIDP 1.0 has no active rendering APIs
  
• MIDP 1.0 has no support for direct access to image pixels (RGB data)
  
• MIDP 1.0 has no support for full screen mode
  
• MIDP 1.0 has no support for audio
  
• MIDP 1.0 requires only HTTP support
  
• MIDP 1.0 cannot query key status (although key events are supported)
  
• The specifications are not always clear, leading to differences in implementations
  
• Some limitations may be avoided by using a vendor-specific API or MIDP 2.0, which obviously reduces the portability of the application

Spruce Up Your Table Views

Setting the background color of your table view is very easy.  All you need to do is set the backgroundColor property to the color you want to see.  For example, I have created a table view here in the app delegate and simply set the background property from here:

UITableViewController *tvc = [[UITableViewController alloc] initWithStyle:UITableViewStyleGrouped];

tvc.view.backgroundColor = [UIColor redColor];

    

[window addSubview:tvc.view];

    

[window makeKeyAndVisible];

If you are using sub-classing, you may also rather set this property in the initWithStyle.

You can use also an image as your background to really spice things up.

Here is that code:

UIView *backgroundView = [[UIView alloc] initWithFrame: window.frame];

backgroundView.backgroundColor = [UIColor colorWithPatternImage:[UIImage imageNamed:@"TableViewBackground.png"]];

[window addSubview:backgroundView];

[backgroundView release];

    

yourTableViewController = [[ATableViewController alloc] initWithStyle:UITableViewStyleGrouped];

yourTableViewController.view.backgroundColor = [UIColor clearColor];

[window addSubview:yourTableViewController.view];

    

[window makeKeyAndVisible];

 

This one takes a little more code - essentially you are putting an image into a view, inserting that into the app window and then setting the background to a transparent color. 

Simply setting the background color of the table view to the image would produce artifacts.  

That is it!  I hope that this tip will add some more pizazz to your apps!

As you can see, the this array is sorted. There you have it!

How To Add A Nice Background Image To Your Grouped Table View

Are you tired of your table views having the standard, boring, gray and white striped background?
Adding a nice image or pattern to your table views is one way of putting a little extra gloss to your UI. This is important, because gloss sells… However, if you have tried to do this yourself you already know that simply inserting an image into your table view will produce ugly artifacts.

What you need to do is create a view with your background image and add that view to your app’s window. Then you must set the table view’s background color to “clearColor”.
Here is how you would do that from the app delegate:

UIView *backgroundView = [[UIView alloc] initWithFrame: window.frame];
backgroundView.backgroundColor = [UIColor colorWithPatternImage:[UIImage imageNamed:@"TableViewBackground.png"]];
[window addSubview:backgroundView];
[backgroundView release];
yourTableViewController = [[ATableViewController alloc] initWithStyle:UITableViewStyleGrouped];
yourTableViewController.view.backgroundColor = [UIColor clearColor];
[window addSubview:yourTableViewController.view];
[window makeKeyAndVisible];

yourTableViewController is declared at the top level of the app delegate and ATableViewController is a subclass of UITableViewController that simply displays the rows and sections in the example.