Layout change events

Layout change events are generated when the screen size or layout is changed. The Symbian platform supports multiple screen resolutions ( scalable UI ). Thus, layout awareness is particularly crucial for those applications that implement a customized UI instead of using automatically scalable AVKON UI components. Applications can detect the changes in layout with, for example, the following methods:

• Controls can override the CCoeControl::HandleResourceChange() to detect the KEikDynamicLayoutVariantSwitch message.

• UI controllers can override the CCoeControl::HandleResourceChange() to detect the KEikDynamicLayoutVariantSwitch message.

The following example code demonstrates the implementation of HandleResourceChange() :

      
       
      
      void CExampleControl::HandleResourceChange( TInt aType )
    {
    CCoeControl::HandleResourceChange(aType);
    //call base class implementation
    if( aType==KEikDynamicLayoutVariantSwitch )
        {
        TRect rect;
        // ask where container's rectangle should be
        // EMainPane equals to area returned by
        //CEikAppUi::ClientRect()
        AknLayoutUtils::LayoutMetricsRect( AknLayoutUtils::EMainPane,rect );
        SetRect( rect );
        }
    }
     

The following example code demonstrates the implementation of HandleResourceChangeL() :

      
       
      
      void CExampleAppUi::HandleResourceChangeL( TInt aType )
    {
    CAknAppUi::HandleResourceChangeL( aType );
    if( aType == KEikDynamicLayoutVariantSwitch )
        {
        // do the re-layout of the components
        }
    // Controls derived from CCoeControl, handled in a
    // container class
    iExampleControlContainer->HandleResourceChange( aType );
    //Must not call this if the components are on the control stack
    //iView->HandleResourceChangeL( aType );
    }
     

If iExampleControlContainer is added to the control stack, it will get its HandleResourceChange() called when a layout is switched and there is no need to call it explicitly.