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The MIDP High-Level API
Sep 26,2007 00:00
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The MIDP High-Level API • Command Processing • Command-Processing Scenario • Screen Navigation • Command Organization At this point, you know how to organize the UI of a basic MIDP application. In any MIDlet more complicated than the first contrived example you saw, you have to define multiple screens. The application moves from screen to screen in response to user input from the keypad, soft keys, or function buttons of a typical mobile device. To build more complex applications, you need to learn how the MIDP accommodates user input and does event processing. This chapter covers the MIDP's high-level API, which defines the abstractions that accommodate handling high-level application events. The high-level API is the first of two APIs for MIDP UI components. The other is the low-level API, which you'll learn about in chapter 5. The term high-level refers to the API's high level of granularity that is provided to the programmer in two areas: • ability to manipulate the look and feel of UI widgets • granularity of information about events and event handling All the UI components under the Screen class hierarchy implement the high-level API. These widgets don't give you the ability to change their look-and-feel. As for events, the information available to the application is at a high level of abstraction. Applications don't have access to concrete input devices. For example, using the Screen abstraction, applications don't have access to information about what physical keys the user presses. The high-level API is designed for business applications that must be portable across many devices. Therefore, the MIDP implementation abstracts the details of things like the implementation to hardware. |