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  PUBLIC "-//OASIS//DTD DITA Task//EN" "task.dtd">
<task id="GUID-A399508A-DE6A-490D-9BFB-4FCF56FF9D4C" xml:lang="en"><title>Derive
a class from the MCoeView class</title><prolog><metadata><keywords/></metadata></prolog><taskbody>
<context>       <p>Derive a class from the <codeph>MCoeView</codeph> class
and provide the definition for each of the following functions:</p><ul>
<li><p><codeblock xml:space="preserve">TVwsViewId ViewId() const</codeblock></p><p>This function
defines the unique identifier of the view within the given application.</p></li>
</ul><ul>
<li><p><codeblock xml:space="preserve">void ViewActivatedL(const TVwsViewId&amp; aPrevViewId,TUid aCustomMessageId,const TDesC8&amp; aCustomMessage)</codeblock></p><p>This is the function is called by the operating system when a view is activated.
The call gets several arguments: the view ID of the previous view that was
displayed (in case a switch back to it is desired), and the identifier and
text of a message that comes from the process that is activating the view.
This message can convey specialized information, such as information on what
to display, from the activating process.</p></li>
</ul><ul>
<li><p><codeblock xml:space="preserve">void ViewDeactivated()</codeblock></p><p>This function is
called by the operating system when a view is deactivated. </p></li>
</ul><ul>
<li><p><codeblock xml:space="preserve">TVwsViewIdAndMessage ViewScreenDeviceChangedL()</codeblock></p><p>This
function has a default implementation. It handles a change to the screen device
returning the value of the <codeph>TVwsViewIdAndMessage</codeph> object. By
default, returns the ID of the active view.</p><p>Cone provides a default
screen device change handler <codeph>CCoeScreenDeviceChangeDefaultHandler</codeph>. <codeph>CCoeScreenDeviceChangeDefaultHandler</codeph> handles
any screen device changes that occur while a view is active. It is used to
activate a default view when a screen flip (changing the screen orientation,
for example, landscape to portrait) occurs, if the currently active view does
not implement <codeph>MCoeView::ViewScreenDeviceChangedL()</codeph>.</p></li>
</ul><p>The following code snippet shows deriving a class from <codeph>MCoeView</codeph> and
implementing the required functions:</p><codeblock xml:space="preserve">class CNewView : public MCoeView
    {
    public:
        //construction
        CNewView( const TVwsViewId&amp; aViewId, CCoeAppUi&amp; aAppUi );
        void ConstructL();
        ~CNewView();
    private:
        // From MCoeView class
        void ViewActivatedL( const TVwsViewId&amp; aPrevViewId, 
                             TUid aCustomMessageId, 
                             const TDesC8&amp; aCustomMessage );    
        void ViewDeactivated();
        TVwsViewIdAndMessage ViewScreenDeviceChangedL();
        void ViewConstructL();
    private:
        CCoeAppUi&amp; iCCoeAppUi;
        TVwsViewId&amp; iViewId;
    };
</codeblock></context>
</taskbody></task>