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<concept id="GUID-1C802DBD-1453-5C69-94D5-FB0229C544D6" xml:lang="en"><title>Uikon
Overview</title><prolog><metadata><keywords/></metadata></prolog><conbody>
<section id="GUID-CB78AFE5-5471-49D0-9740-E3FDA18ED6E9"><title>Purpose</title> <p>Provides a framework for applications.
The framework is fundamental to all GUI applications.</p> </section>
<section id="GUID-74F7D413-3912-477E-A89E-D6BD5F395F9D"><title>Architectural relationships</title> <p>Uikon provides a UI
library layer. It was designed to allow further higher level UI libraries
to be added that can include controls that derive from the ones provided by
Uikon. Avkon provides these higher level UI libraries in Symbian^3 and historically
in the S60 platform. Application developers can use the Uikon APIs directly,
though they should check that there is not a more appropriate Avkon API. </p> <p>The
Uikon application framework extends two lower frameworks:</p> <ul>
<li id="GUID-6941969D-7625-5376-A5D6-5E5B0378D0E7"><p>the Application Architecture
Framework: handles application start-up and accessing the application data
(its <i>document</i>). </p> </li>
<li id="GUID-F1AA0F97-5205-537C-994A-6A3FA811AA72"><p>UI Control Framework:
provides the framework for drawing and handling input to screen controls</p> </li>
</ul> <p> Uikon ties these two frameworks together to provide the framework
for the standard application design. </p> <p>Uikon's framework classes are
extended in turn by:</p> <ul>
<li id="GUID-EF33F5C8-6EA8-5D8A-AE53-A35C692E291A"><p>applications, to implement
appropriate behaviour for their type of data, and for their types of command</p> </li>
<li id="GUID-66353589-7D6B-548E-81A0-3A3515CF8BD8"><p>possibly by UI variant-specific
libraries, to add UI variant-specific behaviour to the application framework</p> </li>
</ul> </section>
<section id="GUID-3B1FA50E-E199-46F3-B8A0-9370BECDE8E2"><title>Description</title> <p>The API has five key concepts: application
(<codeph>CEikApplication</codeph>), document (<codeph>CEikDocument</codeph>),
app UI (<codeph>CEikAppUi</codeph>), UI Environment (<codeph>CEikonEnv</codeph>),
and utilities (<codeph>EikFileUtils</codeph>).</p> <p><b>Application</b> </p> <p>The application class defines properties of the application, such as UID
and caption, and creates a new document.</p> <p>The application base class
is provided by <xref href="GUID-E36E2F07-09E7-32BC-BB83-14DF9232E7D9.dita"><apiname>CEikApplication</apiname></xref>.</p> <p><b>Document</b> </p> <p>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.</p> <p>The
document base class is provided by <xref href="GUID-B33A8A56-D1BE-3E3D-B5AC-F644A5C764DB.dita"><apiname>CEikDocument</apiname></xref>.</p> <p><b>App UI</b> </p> <p>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.</p> <p>The
app UI base class is provided by <xref href="GUID-1185F595-0488-3E93-8D60-6B3A1A3AC32E.dita"><apiname>CEikAppUi</apiname></xref>, which can be
customised by using the resource structure <xref href="GUID-77DF8122-9267-36A6-B5C5-AC989828F2EA.dita"><apiname>EIK_APP_INFO</apiname></xref>.</p> <p><b>UI Environment</b> </p> <p>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 <xref href="GUID-96CA3B4B-993F-36C0-9A5B-DF5CC74EE20E.dita#GUID-96CA3B4B-993F-36C0-9A5B-DF5CC74EE20E/GUID-3587E866-F434-30BA-9CFC-0D40EF8D47FE"><apiname>CEikonEnv::Static()</apiname></xref>),
as a pointer to it is stored in thread-local storage.</p> <p>The UI Environment
is provided by <xref href="GUID-96CA3B4B-993F-36C0-9A5B-DF5CC74EE20E.dita"><apiname>CEikonEnv</apiname></xref>.</p> <p><b>Utilities</b> </p> <p>Utility classes provide easy access for applications
to frequently-used functionality. Notable are <xref href="GUID-EF4568CF-947B-3931-B860-2A63A6B7C275.dita"><apiname>EikFileUtils</apiname></xref> for
file access, and <xref href="GUID-C886511D-1922-3703-843D-1936018788AC.dita"><apiname>EikResourceUtils</apiname></xref> for resource access.</p> </section>
<section id="GUID-E0A48D84-08C6-44BC-B4A0-E8DF472DCB3B"><title>See also</title> <p><xref href="GUID-37E8A48E-09B8-5958-9263-B33EDAE3F7C6.dita">UI
Control Framework Overview</xref> </p> </section>
</conbody></concept>