Ha, I took a long time J2ME, I wrote a HelloWorld, and then I saw the two J2ME books in the past few days. Well, I probably learned about CLDC and MIDP, and I was introduced. Well, I compiled it, the platform. All is better, now it is only a time, the game is planning, now I still look at Ogre.
The 0GRE tutorial of the farmland is still quite detailed, um, check some functions or use it is very convenient, but Yanchen's still more detailed, more, Xixi, wait for him to update him . . .
Hey, I want to go home at 5, I can't buy tickets, 6, 7, but also sold. . . Dizzy, can only go back 4. . Go home can only read the book. . . Reading is also good, otherwise every day before the computer, the book N hasn't seen it for a long time. After reading Thinking in Java and C Edited :)
Turn: J2ME development start
Java Development History believes that people who are familiar with Java evolution history have heard that Java technology is not just called Java, but is called Oak, and the first time is a product designed for embedded systems. Later, because many of the Internet, the many features of Oak are just suitable for use on the network (such as portability, post-compilation program code is small), because the trademark has been registered, so OAK is renamed into Java, since then The ground has become a shining superstar on the network and has become more mature, and many non-expected related applications are slowly generated. Although Java has been used on many enterprise software, it is still very suitable for use in embedded systems. Although Java has been widely used in the table application and Applet development from Java 1.0, Java has returned to its first old road - that is, embedded systems. Application, the Sun Microsystems published two specifications of Embedded Java and Personal Java (also known as PJAVA). The Embedded Java is designed for embedded devices that have no resources, and does not display the embedded device of the device; Personal Java is designed to be designed to connect to the Internet, and have a consumer electronic device that displays a display system (such as color LCD). Then Java version evolves to Java 2, then the three versions of J2EE, J2SE, and J2ME are divided in order to distinguish between various Java applications. However, please remember that since Java 2 divides the Java application area into three blocks, the development of the Java program language will not spread out like Java 1.1, so that everyone will help you all kinds of java The clarification of the application does not cause the chaotic situation that will not be packed in the future. One of them is that when Personal Java has developed to version 1.2, there are also some Java 2 platforms related to security. J2ME J2ME follows the basic principles of "making a single development system for a variety of different devices". So J2ME first distinguish between all embedded devices into two: one is a limited function, and the power supply is also limited (in addition to PDA, mobile phone); the other is relatively better. And relatively sufficient embedded devices on power supply (in all ways, refrigerator, set-top box). Because of these two types of embedded devices, Java introduced a concept called Configuration, and then defined the above operational function, limited electricity, limited to the CONNECTED LIMITED Device Configuration (CLDC) specification; The specification is specified as the Connected Device Configuration (CDC) specification. That is, J2ME first uses all of the embedded devices into two abstract types using the concept of Configuration. In fact, everyone can use Configuration as a specifications for the J2ME for two types of embedded devices, and these specifications define these devices at least in line with the computing capacity, power supply capacity, memory size, etc. A set of categories that can be used in the Java program executed on these devices. The category library defined in these specifications is the subset of Java standard core category libraries and the characteristics of this type. Expansion classifier library. For example, on the CLDC specification, the core category library that can be supported is java.lang. *, Java.io. *, Java.util. *, The expansion class library is Java.MicRoEdition.io. *.
After two main Configuration, J2ME then defines the concept of Profile. Profile is the specification of the architecture in Configuration. The concept of Profile is to make it easier to learn how the Java program is developed on various embedded devices and what features they should have. Therefore, Profile defines the expansion class library that is very relevant to a particular embedded device, and how the user interface on various embedded devices is defined in the Profile. The expansion classifier library defined in Profile is established based on the core class fuse library defined in the underlying Configuration. Although the J2ME standard is wide, it is easy to grasp the reason for grasp the standard division. In the field of rapid development of this technology, we cannot limit our attention to the standard literal meaning, but to master, grasp the spirit. For example, the specific minimum memory requirements in the definition of CLDC and CDC is only "smallest", and with the rapid development of hardware capabilities, it is likely that some boundaries will become blurred. PDA should be a range of CLDC, but CDC is implemented on the iPAQ of Compaq. The next generation of PDAs in the future is not surprising, and it is entirely possible to implement CDC. However, from the perspective of the function, it should be a CLDC and the PDA Profile for the conditions of the PDA. By then, the specific implementation is to see the choice of manufacturers and developers. It should also be noted that because profile is built above Configuration, the Profile must configure support. Some articles are saying that MIDP needs at least 256K when speaking the MIDP's memory demand. This means the MIDP itself. Some articles say that MIDP requires a minimum of 768K, then because the 512K required to be the foundation CLDC is going in. CLDC CLDC is a configuration of a device for less than 512KB memory Footprint. CLDC uses KVM, which is highly optimized JVM, which is a 16-bit or 32-bit microprocessor, 160 to 512 kB memory-based low-end, network connection, battery-driven devices. Typical memory requirements are 128KB to store KVM and related libraries. More information about KVM can be obtained from Sun's KVM white pages. For networking, CLDC is targeted for limited and intermittent wireless connecting devices, all applications running over J2ME CLDC should be run on any other high-end Java VM. Of course, this requires the support of the CLDC library. CLDC configuration focuses on I / O, networking, security issues, international issues, and core Java libraries, etc. related areas. The fields related to event processing, user and application interaction, application survival management, etc. are processed by profile. Using interface definitions (for specific devices, such as pager, mobile phones, and PDA) are also within the range of the PROFILE layer and use the J2ME configuration. Mobile Information Device PROFILE (MIDP) is a J2ME profile that defines a specification related to user interfaces using CLDC configuration devices. CLDC Gets vast majority of classes from J2SE, but some new categories for small memory Footprint devices are not available from J2SE APIs. For specific information about the class from J2SE, inheritance and new CLDC classes, refer to the contents of 6.2 and 6.3 of the CLDC specification 1.0A version. Some exceptions in the Java language specification are no floating point support, and there is no completion support and limited error handling capabilities of class instances.
