From Forum Nokia Wiki

ID	CS000869	Creation date	March 28, 2008
Platform	S60 3rd Edition, FP1	Tested on devices	Nokia N95
Category	Symbian C++	Subcategory	UI

Keywords (APIs, classes, methods, functions): CCoeControl, TKeyEvent, CEikScrollBarFrame, TAknDoubleSpanScrollBarModel

Overview

This code snippet shows how to add scrollbars to a container control that has custom controls and how to show only visible components and search for more of them in view top and bottom.

This example extends the existing code snippet CS000868 - Custom control: Focusing. Check the See also section of this article for other snippets of the Custom Control series.

CMyContainerControl - Header

Add these methods and member data to the CMyContainerControl component header.

MoveFocusUpL() Moves focus to ask for more components to the screen at the bottom of the view
MoveFocusDownL() Moves focus to ask for more components to the screen at the bottom of the view
UpdateScrollBarFrameL() Updates scroll bar
ShowNextItem() Searches for more items to the screen at the bottom of the view
ShowPrevItem() Searches for more items to the screen at the top of the view

#include <eiksbfrm.h>
 
private:
    void ShowNextItem();
    void ShowPrevItem();
    void MoveFocusUpL();
    void MoveFocusDownL();
    void UpdateScrollBarFrameL();
private:
    CEikScrollBarFrame*                   iScrollBarFrame;
    TAknDoubleSpanScrollBarModel          iHDsSbarModel;
    TAknDoubleSpanScrollBarModel          iVDsSbarModel;        
    TInt                                  iFocusedIndex;

CMyContainerControl - Source

Create scroll bar in CMyContainerControl::ConstructL()

// Creating Scroll Bars
iScrollBarFrame = new ( ELeave ) CEikScrollBarFrame( this, NULL );
iScrollBarFrame->CreateDoubleSpanScrollBarsL( ETrue, EFalse );
iScrollBarFrame->SetTypeOfVScrollBar( CEikScrollBarFrame::EDoubleSpan );
iScrollBarFrame->SetScrollBarVisibilityL( CEikScrollBarFrame::EOff, 
CEikScrollBarFrame::EOff );

Update scroll bar data in CMyContainerControl::UpdateScrollBarFrameL() The method will be called in CMyContainerControl::AddControlL() after adding components into this container control.

void CMyContainerControl::UpdateScrollBarFrameL()
    {
    TInt controlsHeight = 0; // Height of the controls
    TInt height = 0; // This view height
 
    // Calculate components height
    CCoeControlArray::TCursor cursor = Components().Begin();
    CCoeControl* ctrl = NULL;
    while ((ctrl = cursor.Control<CCoeControl>()) != NULL)
        {
        controlsHeight += ctrl->MinimumSize().iHeight;
        cursor.Next();
        }
 
    // This view height
    height = Rect().Height();
 
    // Set teh scrollbar visible if fields do not fit the screen
    if( controlsHeight > height && 
        iScrollBarFrame->VScrollBarVisibility() == 
        CEikScrollBarFrame::EOff)
        {
        iScrollBarFrame->SetScrollBarVisibilityL(
                CEikScrollBarFrame::EOff, // horizontal
                CEikScrollBarFrame::EOn); // vertical
        }
    // Hide the scrollbar if fields fit the screen
    else if ( controlsHeight <= height && 
              iScrollBarFrame->VScrollBarVisibility() == 
              CEikScrollBarFrame::EOn)
        {
        iScrollBarFrame->SetScrollBarVisibilityL(
                CEikScrollBarFrame::EOff, // horizontal
                CEikScrollBarFrame::EOff); // vertical
        }
 
    // Update scroll bar position
    iVDsSbarModel.SetScrollSpan(Components().Count());
    iVDsSbarModel.SetWindowSize(1);
    iVDsSbarModel.SetFocusPosition(iFocusedIndex);
    TEikScrollBarFrameLayout layout;
    layout.iTilingMode = TEikScrollBarFrameLayout::EInclusiveRectConstant;
    TRect rect = Rect();
    iScrollBarFrame->TileL(&iHDsSbarModel,&iVDsSbarModel,rect,rect,layout);
    iScrollBarFrame->SetVFocusPosToThumbPos(iVDsSbarModel.FocusPosition());
    }

CMyContainerControl::MoveFocusUpL() moves active component focus and asks to show more components if the cursor reaches the screen top.

void CMyContainerControl::MoveFocusUpL()
    {
    CCoeControlArray::TCursor cursor = Components().Begin();
    CCoeControl* ctrl = NULL;
    CCoeControl* prevCtrl = NULL;
    while ((ctrl = cursor.Control<CCoeControl>()) != NULL)
        {
        if (ctrl->IsFocused())
            {
            if (prevCtrl)
                {
                // Set focus to previous control
                ctrl->SetFocus(EFalse);
                prevCtrl->SetFocus(ETrue);
                iFocusedIndex--;
 
                // Focus is over the view?
                if (iFocusedIndex > 0 && !prevCtrl->IsVisible())
                    {
                    ShowPrevItem();
                    }
                break;
                }
            else
                {
                break; // First control is already focused
                }
            }
        prevCtrl = ctrl;
        cursor.Next();
        }
 
    UpdateScrollBarFrameL();
    }

CMyContainerControl::MoveFocusDownL() moves active component focus and asks to show more components if the cursor reaches the screen bottom.

void CMyContainerControl::MoveFocusDownL()
    {
    CCoeControlArray::TCursor cursor = Components().Begin();
    CCoeControl* ctrl = NULL;
    CCoeControl* nextCtrl = NULL;
    while ((ctrl = cursor.Control<CCoeControl>()) != NULL)
        {
        if (ctrl && ctrl->IsFocused())
            {
            cursor.Next();
            nextCtrl = cursor.Control<CCoeControl>();
            if (nextCtrl)
                {
                // Set focus to next control
                ctrl->SetFocus(EFalse);
                nextCtrl->SetFocus(ETrue);
                iFocusedIndex++;
 
                // Focus is over the view?
                if (!nextCtrl->IsVisible())
                    {
                    ShowNextItem();
                    }
                break;
                }
            else
                {
                break; // Last control is already focused
                }
            }
        cursor.Next();
        }
 
    UpdateScrollBarFrameL();
    }

void CMyContainerControl::ShowNextItem() and void CMyContainerControl::ShowPrevItem() find more components to view and set them to the correct position.

void CMyContainerControl::ShowNextItem()
    {
    TPoint position;
 
    // Goes throught all components of this container control
    CCoeControlArray::TCursor cursor = Components().Begin();
    CCoeControl* ctrl = NULL;
    TBool focusedFound = EFalse;
    while ((ctrl = cursor.Control<CCoeControl>()) != NULL)
        {
        if (ctrl && ctrl->IsFocused())
            {
            focusedFound = ETrue;
            }
 
        if (focusedFound)
            {
            // Set size
            TSize size = ctrl->MinimumSize();
            size.SetSize(Rect().Width(),size.iHeight);
            ctrl->SetSize(size);
 
            // Does it fit to the screen?
            if ((position.iY + size.iHeight) >= Rect().iBr.iY)
                {
                ctrl->MakeVisible(EFalse);
                focusedFound = EFalse; // Let rest components be MakeVisible(EFalse) 
                }
            else
                {
                ctrl->MakeVisible(ETrue);
 
                // Set position
                ctrl->SetPosition(position);
 
                // Store position of last component
                position.iY += size.iHeight;
                }
            }
        else
            {
            ctrl->MakeVisible(EFalse);
            }
        cursor.Next();
        }
    }
 
 
void CMyContainerControl::ShowPrevItem()
    {
    TPoint position;
    position.iY = Rect().iBr.iY;
 
    // Goes throught all components from the last -> to the first one
    CCoeControlArray::TCursor cursor = Components().End();
    CCoeControl* ctrl = NULL;
    TBool focusedFound = EFalse;
    while (cursor.Prev())
        {
        ctrl = cursor.Control<CCoeControl>();
        if (ctrl && ctrl->IsFocused())
            {
            focusedFound = ETrue;
            }
 
        if (focusedFound)
            {
            // Set size
            TSize size = ctrl->MinimumSize();
            size.SetSize(Rect().Width(),size.iHeight);
            ctrl->SetSize(size);
 
            // Fix position
            position.iY -= size.iHeight;
 
            if ((position.iY) <= Rect().iTl.iY-2)
                {
                // Does not fit anymore
                ctrl->MakeVisible(EFalse);
                focusedFound = EFalse; // Let rest components be MakeVisible(EFalse)
                }
            else
                {
                ctrl->MakeVisible(ETrue);
 
                // Set position
                ctrl->SetPosition(position);
                }
            }
        else
            {
            ctrl->MakeVisible(EFalse);
            }
        }
    }

Postconditions

Custom control has scrollbars that show the position of the focus in the view. More components will be shown when reaching the bottom or top of the view.

See also

Custom Control Series:

• CS000859 - Custom control How to define custom control
• CS000860 - Custom control: Construct from resource Creating a control from a resource
• CS000861 - Custom control: Container control Creating a container control
• CS000868 - Custom control: Focusing Handling key events and changing active custom control focus
• CS000870 - Custom control: In dialog Adding a custom control into CAknDialog
• File:CustomControl.zip Example code patch