Uikon Overview

Purpose

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

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:

the Application Architecture Framework: handles application start-up and accessing the application data (its document).
UI Control Framework: provides the framework for drawing and handling input to screen controls

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

Uikon's framework classes are extended in turn by:

applications, to implement appropriate behaviour for their type of data, and for their types of command
possibly by UI variant-specific libraries, to add UI variant-specific behaviour to the application framework

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.