Symbian
Symbian OS Library

SYMBIAN OS V9.3

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Uikon Overview


Purpose

Provides the top-layer of the framework for applications. The framework is fundamental to all GUI applications.

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Architectural relationships

Uikon provides a UI library layer that is common to all Symbian OS phones. UI variants add further UI libraries that can include controls that derive from the ones provided by Uikon. Application developers can use the Uikon APIs directly, though they should check that there is not a more appropriate phone-specific API available in the UI variant's own libraries.

The Uikon application framework extends two lower frameworks:

Uikon ties these two frameworks together to provide the framework for the standard application design.

Uikon's framework classes are extended in turn by:

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Description

The API has five key concepts: application (CEikApplication), document (CEikDocument), app UI (CEikAppUi), UI Environment (CEikonEnv), and utilities (EikFileUtils).


Application

The application class defines properties of the application, such as UID and caption, and creates a new document.

The application base class is provided by CEikApplication.


Document

The document class represents the data model for the application. In file-based applications, it stores and restores the application's data. It handles requests to edit a document by creating an app UI.

The document base class is provided by CEikDocument.


App UI

The app UI is the central user interface class. It creates and owns controls to display the application data, and centralises handling of command input from standard controls such as menus and toolbars.

The app UI base class is provided by CEikAppUi, which can be customised by using the resource structure EIK_APP_INFO.


UI Environment

The UI Environment provides a large number of assorted UI functionality, particularly simple access to information and query dialogs, and access to standard system UI resources (bitmaps and fonts). Every object in a GUI application can access a UI Environment (through CEikonEnv::Static()), as a pointer to it is stored in thread-local storage.

The UI Environment is provided by CEikonEnv.


Utilities

Utility classes provide easy access for applications to frequently-used functionality. Notable are EikFileUtils for file access, and EikResourceUtils for resource access.

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See also

UI Control Framework Overview