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J2ME in a Nutshell phần 2

nó là vô cùng không bao giờ bạn cần phải viết phần mềm hoạt động duy nhất với các API được cung cấp bởi CLDC, vì nó chứa không có gì cho phép tương tác với người sử dụng, thiết bị lưu trữ, hoặc mạng. CLDC là nhằm mục đích để được một lớp cơ sở trên đầu | J2ME in a Nutshell Chapter 3. The Mobile Information Device Profile and MIDlets The Connected Limited Device Configuration provides the basis for running Java on devices that have insufficient resources to support a complete virtual machine together with a full version of the J2SE core packages. However if you are an application developer it is extremely unlikely that you will ever need to write software that works solely with the APIs provided by CLDC because it contains nothing that allows for interaction with users storage devices or a network. CLDC is intended to be a base layer on top of which a range of profiles that provide the missing facilities can be provided in a form suitable for the class of device for which each profile is designed. The Mobile Information Device Profile or MIDP for short is one such profile intended for use on small footprint devices with a limited user interface in the form of a small screen with some kind of input capability. This chapter introduces MIDP in the following two chapters we ll look in more detail at how it supports user interfaces networking and persistent storage of information. 3.1 MIDP Overview MIDP is a version of the Java platform based on CLDC and KVM that is aimed at small footprint devices principally cell phones and two-way pagers. It is also suitable for running on PDAs and an implementation is available for PalmOS Version 3.5 and higher. In the longer term it is intended that these devices use the PDA profile which is also hosted by CLDC. The MIDP specification was developed under the Java Community Process and is available for download from http jcp.org jsr detail 37.jsp. The logical position of MIDP within the software architecture of a device that implements it is shown in Figure 3-1. The software that implements MIDP runs in the KVM supplied by CLDC and provides additional services for the benefit of application code written using MIDP APIs. MIDP applications are called MIDlets. As Figure 3-1 shows .