J2ME learning notes finishing (1)

Author: Natsuhiko end

I have always wanted to write something to learn J2ME to make a summary. Since last time the notebook inexplicably lost after the bedroom, I have never written J2ME's study notes. I finally got a courage to make a pen, and I also prepared to learn J2ME brothers. The sisters play a piece of jade, huh, huen, hopes that everyone is disappointing.

Let's start from the most basic beginning ~

J2ME's full name is Java2 Platform Micro Edition, and its technical architecture is as follows

Optional Package Profile Configuration

Optional package is a vendor selective implementation. Profile is a high-level API set for special hardware regulations. Configuration is the role of defining hardware functions and low-level APIs.

Start from the bottom of the CONFIGURATION, it is a J2ME specifying the specification of the embedded device to execute the Java program. J2ME is limited, and the embedded device of the calculation function is called Connected Limited Device. If these devices can be implemented, if they can perform Java The program must be observed, and these specifications are defined in the Connected Limited Device Configuration, referred to as CLDC, similar to a connected, resource relatively unlimited device, is called Connected Device, and there is also a CDC specification. The phone we usually use is a CONNECTED LIMITED DEVICE. The mobile phone that supports J2ME must support the support of the CLDC specification. In the current point of view, there are 1.0 and 1.1, the biggest difference is the latter support floating point operation, and the former does not support, CDC 1.0 and CDC1.1 core class libraries (java.lang. *, Java .io. *, java.util. *) and J2se have almost no difference. CLDC1.0 is different, and CLDC1.1 is relatively relatively enhanced with CLDC1.0 function. The minimum amount of memory is also raised from 160K to 192K. The support extension library added by CLDC is javax.microedition.IO. *, Etc.

View CLDC Class Library Documents

You can get the following information, in order to make it easy for everyone, I have made a few big categories:

System class:

Java.lang.object

Java.lang.class

Java.lang.Runtime

Java.lang.system

Java.lang.thread

Java.lang.Runnable (interface)

Java.lang.string

Java.lang.StringBuffer

Java.lang.Throwable

Data Type Category:

Java.lang.Boolean

Java.lang.byte

Java.lang.short

Java.lang.integer

Java.lang.long

Java.lang.float (start support from version 1.1)

Java.lang.double (start support from version 1.1)

Java.lang.Character

Collection container:

Java.util.Vector

Java.util.stack

Java.util.hashable

Java.util.enumeration (interface)

Input / output class:

Java.io.inputStream

Java.io.outputstream

Java.io.byteArrayInputStream

Java.io.byteArrayoutputstream

Java.io.DataInput (interface)

Java.io.Dataoutput (interface)

Java.io.DataOutputSteam

Java.io.DataInputStream

Java.io.reader

Java.io.writer

Java.io.inputsteamReader

Java.io.OutputStreamReader

Java.io.printStream

Calendar and time class:

Java.util.calendar

Java.util.date

Java.util.timezone

Other additional classes:

Java.util.random

Java.lang.math

Error class:

Java.lang.Error

Java.lang.noclassdefounderror (support from version 1.1)

Java.lang.OutofMemoryError

Java.lang.virtualMachineError

Abnormal class:

Java.lang.exception

Java.lang.arithMeticexception

Java.lang.ArrayIndexOutofboundsexception

Java.lang.ArrayStoreException

Java.lang.classcastexception

Java.lang.classNotFoundException

Java.lang.illegaCCssexception

Java.lang.illegalargumentException

Java.lang.illegalmonitorStateException

Java.lang.illegalthreadStateException

Java.lang.indexOutofboundSexception

Java.lang.instantiationException

Java.lang.InterruptedException

Java.lang.negativeAraysizeException

Java.lang.nullpointerException

Java.lang.RuntimeException

Java.lang.NumberFormATexception

Java.lang.securityException

Java.lang.StringIndexOutofboundsexception

Java.util.emptyStackException

Java.util.emptynosuchelementexception

Java.io.eofexception

Java.io.InterruptedioException

Java.io.ioException

java.io.unsupportedEncodingexception

Java.io.utfdataFormatexception

Weak reference: (starting from version 1.1)

Java.lang.ref.reference

Java.lang.ref.weakreference

The following is a CLDC1.1 extended class library:

Javax.microedition.midlet. *

Javax.microedition.lcdui. *

Javax.microedition..rms. *

Javax.microedition..io. *

Javax.microedition.lcdui.game. *

Javax.microedition.pki. *

Javax.microedition..media. *

Javax.microedition.media.control. *

Let's say Profile, since Profile is built on the Configuration, its specification is naturally not lower than the Configuration, and the profile we usually has Mobile Information DEVICE PROFILE (MIDP), for mobile phones and Pager, and other mobile devices. There is also a common Profile, Information Module Profile, is designed for mobile devices without screens. At present, MIDP, the highest specification is 2.0, and the hardware requirements are:

Memory: 256KB non-volatile memory can be used by MIDP components, 8KB non-volatile memory works creates persistence data, 128KB volatile memory can be used in virtual machine runtime environments.

Display: Screen size 96 * 54, display depth: 1 bit, pixel shape (aspect ratio): 1: 1.

Enter: One-hand keyboard or hands keyboard or touch screen.

Network: two-way, wireless, can be intermittent, limited bandwidth.

Sound: Play different tone capabilities, can be obtained through software algorithms through a dedicated hardware.

In the J2ME specification, manufacturers also define packages that manufacturers can choose to implement, that is Optional Packages, usually different products from different manufacturers will have some different functions, then manufacturers can use the Optioanl Packages specification to achieve specific functionality of certain products. Corresponding API.

Then we usually say J2ME development, most of them are all MIDP programming, then let's first see the explanation of several nouns:

MIDlet: A basic unit of executable application mobile phone program.

MIDLET Suite: Many MIDLETs constructed are generally called MIDP Application (MIDP applications).

The relationship between MIDlet and MIDlet Suite is shown below

JAR file (jar file, .jar file)

It is actually wrapped in the file of MIDlet Suite, which belongs to the ZIP compression format.

JAD file (Descriptor file, .jad file)

A text file used to describe the basic information of the MIDlet Suite, it is an external file (not existing inside the JAR file, an independent file).

The only relationship is as shown below:

Finally, you should introduce the application manager (Java Application Manager), it is important, it is responsible for the execution of the MIDlet and its lifecycle. It is a native program used to perform J2ME.