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This chapter is from the book

This chapter is from the book

Chapter Summary

In this chapter you've learned about the basic organization and structure of MIDP applications. The center of the MIDP programming model is the MIDlet.

The main components of a MIDlet's structure are the MIDlet instance, a Display instance, and one or more Displayable widgets, which are UI components.

MIDlet objects are associated with a Display object. MIDlets create Displayable widgets, which are UI components, and request that they be displayed on the device's screen. The display manages the device's screen and the visibility of the UI widgets.

The abstract Screen class is the first of two main types that categorize all Displayable objects. The Screen class is the central display abstraction. The Form class is a concrete subclass of Screen. Only one Screen is visible at any moment in a MIDlet's life.

All MIDlets have associated properties and attributes. Properties are standard system properties defined by the CLDC specification. They pertain to the platform and are maintained and managed by the application management system. Attributes are associated with MIDlets. There are required attributes that are available to all MIDlets, and there are optional attributes. Additionally, there are application-specific attributes that can be defined by the MIDlet author. Attributes exist in the application JAD file and are managed by the device AMS software during runtime.

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