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    10 <!DOCTYPE concept

    11   PUBLIC "-//OASIS//DTD DITA Concept//EN" "concept.dtd">

    12 <concept id="GUID-68B999C2-0993-4804-9624-42C3D88BE5C7" xml:lang="en"><title>View

    13 architecture</title><prolog><metadata><keywords/></metadata></prolog><conbody>

    14 <p>The following image illustrates the components of the view architecture

    15 approach.</p>

    16 <fig id="GUID-A4D968BE-B048-424C-94B5-FAAA7B14C5D5"><title>View architecture classes</title><image href="GUID-2B50C6B1-E1E8-44E6-840B-7FAA206E6C26_d0e44021_href.png"/></fig>

    17 <p>Symbian platform applications that follow the view architecture require:</p>

    18 <ul>

    19 <li><p>a <xref href="GUID-FD2CDEB8-0784-4BE5-A775-170F57D71BBC.dita">UI

    20 controller</xref> derived from <xref href="jar:GUID-759FBC7F-5384-4487-8457-A8D4B76F6AA6.jar!/html/classCAknViewAppUi.html" format="application/java-archive"><parmname>CAknViewAppUi</parmname></xref></p>

    21 </li>

    22 <li><p>a <xref href="GUID-DAC32BB9-C0EB-42FF-A596-C2F1A90A4BD7.dita">view

    23 controller</xref> derived from <xref href="jar:GUID-759FBC7F-5384-4487-8457-A8D4B76F6AA6.jar!/html/classCAknView.html" format="application/java-archive"><parmname>CAknView</parmname></xref></p>

    24 </li>

    25 <li><p>a <xref href="GUID-DAC32BB9-C0EB-42FF-A596-C2F1A90A4BD7.dita">view</xref> or

    26 views derived from <xref href="jar:GUID-35228542-8C95-4849-A73F-2B4F082F0C44.jar!/sdk/doc_source/reference/reference-cpp/Control_Environment/CCoeControlClass.html" format="application/java-archive"><parmname>CCoeControl</parmname></xref></p>

    27 </li>

    28 </ul>

    29 <p>The view architecture only allows one view to be active in each application.

    30 If a new view is switched to within an application, the current view is immediately

    31 deactivated, so this architectural approach is <i>not</i> appropriate in the

    32 following cases:</p>

    33 <ul>

    34 <li><p>Applications with any view that cannot cleanly handle unexpected

    35 activation of another view in that application.</p></li>

    36 <li><p>Applications that provide views that can be nested over other

    37 applications, except where embedding is used.</p></li>

    38 <li><p>Applications that provide controls that can be used inside

    39 other applications (for example, using a Web control inside an e-mail viewer

    40 to show an e‑mail with HTML content).</p></li>

    41 </ul>

    42 <p>Typical responsibilities in this architecture are:</p>

    43 <ul>

    44 <li><p><xref href="jar:GUID-759FBC7F-5384-4487-8457-A8D4B76F6AA6.jar!/html/classCAknViewAppUi.html" format="application/java-archive"><parmname>CAknViewAppUi</parmname></xref>-derived

    45 class acts as a <xref href="GUID-FD2CDEB8-0784-4BE5-A775-170F57D71BBC.dita">UI

    46 controller</xref>:</p>

    47 <itemgroup>

    48 <ul>

    49 <li><p>It creates one or more <xref href="jar:GUID-759FBC7F-5384-4487-8457-A8D4B76F6AA6.jar!/html/classCAknView.html" format="application/java-archive"><parmname>CAknView</parmname></xref>-derived

    50 view controllers.</p></li>

    51 <li><p>It handles <xref href="GUID-EF7FF39E-929F-4767-B475-5D582D37BB32.dita">events</xref> that

    52 are not handled by the view controllers.</p></li>

    53 <li><p>To switch between views, it activates and deactivates views.</p>

    54 </li>

    55 <li><p>It handles menu <xref href="GUID-4941C035-C359-4968-9BD5-31F44EE5F810.dita">commands</xref> passed

    56 to it by the view controllers.</p></li>

    57 <li><p>It receives events such as <xref href="GUID-DD15F24B-0786-4531-A6C5-A5E70EBE2732.dita">layout</xref> and <xref href="GUID-3B441CDC-AB7A-4D8D-A595-57C21E1D426C.dita">foreground</xref> notifications

    58 from the run-time environment.</p></li>

    59 </ul>

    60 </itemgroup>

    61 </li>

    62 <li><p><xref href="jar:GUID-759FBC7F-5384-4487-8457-A8D4B76F6AA6.jar!/html/classCAknView.html" format="application/java-archive"><parmname>CAknView</parmname></xref>-derived

    63 class acts as a <xref href="GUID-FD2CDEB8-0784-4BE5-A775-170F57D71BBC.dita">view

    64 controller</xref></p>

    65 <itemgroup>

    66 <ul>

    67 <li><p>It creates one of more <xref href="jar:GUID-35228542-8C95-4849-A73F-2B4F082F0C44.jar!/sdk/doc_source/reference/reference-cpp/Control_Environment/CCoeControlClass.html" format="application/java-archive"><parmname>CCoeControl</parmname></xref>-derived

    68 views.</p></li>

    69 <li><p>It handles registering controls for <xref href="GUID-E402616A-7ED8-45AC-B836-99C3A3760B33.dita">key

    70 event handling</xref>.</p></li>

    71 <li><p>It handles menu <xref href="GUID-4941C035-C359-4968-9BD5-31F44EE5F810.dita">commands</xref>.</p>

    72 </li>

    73 </ul>

    74 </itemgroup>

    75 </li>

    76 <li><p><xref href="jar:GUID-35228542-8C95-4849-A73F-2B4F082F0C44.jar!/sdk/doc_source/reference/reference-cpp/Control_Environment/CCoeControlClass.html" format="application/java-archive"><parmname>CCoeControl</parmname></xref>-derived

    77 view:</p>

    78 <itemgroup>

    79 <ul>

    80 <li><p>Shows application data and state on the screen.</p></li>

    81 </ul>

    82 </itemgroup>

    83 </li>

    84 </ul>

    85 <p>For information on the <xref href="jar:GUID-759FBC7F-5384-4487-8457-A8D4B76F6AA6.jar!/html/classCAknApplication.html" format="application/java-archive"><parmname>CAknApplication</parmname></xref> and <xref href="jar:GUID-759FBC7F-5384-4487-8457-A8D4B76F6AA6.jar!/html/classCAknDocument.html" format="application/java-archive"><parmname>CAknDocument</parmname></xref>-derived

    86 classes, see <xref href="GUID-BDDDF68F-F7C3-43AF-8B6C-C77C701FD2A9.dita">Framework

    87 requirements for GUI applications</xref>.</p>

    88 </conbody></concept>