Handling scalability in Symbian C++ on touch enabled device

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Article Metadata

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Tested with

Devices(s): Nokia 5800 XpressMusic

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Compatibility

Platform(s): S60 5th Edition

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Article

Keywords: CAknAppUi::HandleResourceChangeL(), CCoeControl::HandleResourceChange()

Created: tepaa (03 Oct 2008)

Last edited: hamishwillee (14 Jun 2012)

Overview

S60 5th Edition supports touch events. All AVKON UI controls handle touch UI events and you do not need to implement anything new.

If you implement your own custom CCoeControl UI control, it is important to handle its scalability. If scalability is not handled, the S60 platform may not receive touch events, or it may receive touch events for the incorrect control because the correct location of the touch event may not be known.

MMP file

The following libraries are required:

LIBRARY cone.lib

Handle resoucre change

Custom CCoeControl-derived classes must be able to react to changes in UI layout.

void CMyControl::HandleResourceChange(TInt aType)
    {
    // Call base class implementation
    CCoeControl::HandleResourceChange(aType);
    if ( aType==KEikDynamicLayoutVariantSwitch )
        {
        // Setting new rect for this control
        TRect rect;
        AknLayoutUtils::LayoutMetricsRect(
        AknLayoutUtils::EMainPane,rect);
        // SetRect() causes calling components SizeChanged()
        SetRect(rect);
        }
    }

Handle scalability in your application CAknAppUi class:

void CMyAppUi::HandleResourceChangeL(TInt aType)
        {
        // Call base class implementation
        CAknAppUi::HandleResourceChangeL( aType );
        if ( aType == KEikDynamicLayoutVariantSwitch )
             {
             // Do the re-layout of the components
             // TODO: do some layout impl here if needed
             }
 
        // NOTE: Must not call this if the components are on the control stack
        // iMyView->HandleResourceChangeL( aType );
 
        // NOTE: If CMyControl is in control stack is 
        // CMyControl::HandleResourceChange() called automatically
        }

Adding controls into control stack

If a control is in the control stack, it will receive key events and resource change events.

In traditional Symbian C++ applications, when CMyAppUi is derived from CAknAppUi:

void CMyAppUi::ConstructL ( )
    {
    // Initialise app UI with standard value.
    BaseConstructL (EAknEnableSkin | EAknTouchCompatible);
 
    // Create view
    iAppView = CMobilePaintAppView::NewL (ClientRect ( ) );
 
    // --> Add view into control stack    
    AddToStackL( iAppView ); 
    }

When using view switching CMyAppUi is derived from CAknViewAppUi. The control is added into the control stack when the view is activated.

void CMyView::DoActivateL(const TVwsViewId& aPrevViewId,
    TUid aCustomMessageId, const TDesC8& aCustomMessage)
    {
    if (!iContainer)
        {
        iContainer = CMyControl::NewL(ClientRect());
 
        // -->  Add view into control stack
        AppUi()->AddToStackL (*this, iContainer);
        }
    }

Postconditions

Scalability of the control is handled.

See also

S60 Platform: Image Converter Example