Wireless Java

The MIDP GUI APIs

Because of the issues outlined earlier, the MIDP contains its own abbreviated GUI, which is much different from AWT. The MIDP GUI consists of both high-level and low-level APIs, each with their own set of events. This chapter discusses and shows examples of using objects from both the high-level and low-level APIs. Handling events from APIs, however, is deferred to the next chapter.

The high-level API is designed for applications where portability between mobile information devices is important. To achieve portability, the API employs a high-level abstraction and gives you little control over its look and feel. For example, you cannot define the visual appearance (shape, color, or font) of the high-level components. Most interactions with the components are encapsulated by the implementation; the application will not be aware of them. Consequently, the underlying implementation does the necessary adaptation to the device’s hardware and native user interface style. Classes that implement the high-level API all inherit the javax.microedition.lcdui.Screen class.

The low-level API provides little abstraction. It is designed for applications that need precise placement and control of graphic elements, as well as access to low-level input events. This API gives the application full control over what is being drawn on the display. The javax.microedition.lcdui.Canvas and javax.microedition.lcdui.Graphics classes implement the low-level API. However, we should point out ...