Scrollbar events in 5th edition-优快云博客

本文介绍了一个自定义控件中滚动条的方向和移动跨度的实现方法。通过Symbian C++编程，详细展示了如何创建滚动条、定义滚动条大小，并处理滚动事件。

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This article demonstrates how to get the scrollbar direction and movement spans.

Header:

class CMyControl: public CCoeControl, public MEikScrollBarObserver
{
     public:// Constructors and destructor
        ~CMyControl();
        static CMyControl* NewL(TRect aRect);
        static CMyControl* NewLC(TRect aRect);

     private:
         CMyControl();
         void ConstructL(TRect aRect);
         void Draw( const TRect& aRect ) const;
         virtual void HandlePointerEventL(const TPointerEvent& aPointerEvent);
         TInt CountComponentControls() const;
         CCoeControl* ComponentControl( TInt aIndex ) const;
         void CreateScrollBar();

     private:///MEikScrollBarObserver
         void HandleScrollEventL(CEikScrollBar* aScrollBar,TEikScrollEvent aEventType );

     protected:
         void SizeChanged();

     private:
        CEikScrollBarFrame* iSBFrame;
        TInt                iScrollSpan;
        TInt                iScrollPos;
TBool iIsScrollDown;

};

Cpp:

// Implementation of scroll bar in custom control along with number of movement by scrollbar in one Drag.
// ScrollBar in symbian c++ ("Symbian c++").

void CMyControl::CreateScrollBar()
{
         iScrollPos=-1;// initial scroll pos is -1 as 0 specify the first span/drag.
         iScrollSpan=1;// scrollbar moves by one item at a time
         iSBFrame=new ( ELeave ) CEikScrollBarFrame( this,this);
         iSBFrame->SetScrollBarVisibilityL(CEikScrollBarFrame::EOff,CEikScrollBarFrame::EOn);
         iSBFrame->CreateDoubleSpanScrollBarsL(ETrue, EFalse);// create scrollbar
         iSBFrame->SetTypeOfVScrollBar(CEikScrollBarFrame::EDoubleSpan);//type of scrollbar
}

void CMyControl::SizeChanged()
{
         // Here you are required to define the size of your scrollbar//
          TInt listStatusPaneHeight=60;
          TEikScrollBarFrameLayout layout;
          TEikScrollBarModel       myModel;
          TEikScrollBarModel       myModel2;
          myModel.iThumbSpan=1;
          myModel.iScrollSpan =iScrollSpan;
          layout.iTilingMode=TEikScrollBarFrameLayout::EInclusiveRectConstant;
          TRect fullRect =TRect(TPoint(Rect().iTl.iX,Rect().iTl.iY+listStatusPaneHeight),TSize(Rect().Size().iWidth,Rect ().Size().iHeight-listStatusPaneHeight));
          TRect inclRect = fullRect;
          if(iSBFrame)
    {
            TBool stat = iSBFrame->TileL(&myModel2, &myModel, fullRect, inclRect, layout);
        iSBFrame->DrawScrollBarsNow();
          }
    }

void CMyControl::HandleScrollEventL(CEikScrollBar* aScrollBar,TEikScrollEvent aEventType )
        {
        switch(aEventType)
           {
             case EEikScrollThumbDragVert:
                 {
                   CEikScrollBar* sb= iSBFrame->VerticalScrollBar();// get an object of your scroll bar
                   TInt pos=sb->ThumbPosition();/// it will provide new position of scrollbar
                  if(iScrollPos<pos)
                   {
                     iScrollPos=pos;/// moving down number of scroll span
                     iIsScrollDown=ETrue;
                   }
                  else
                   {
                     iScrollPos=pos;/// moving down number of scroll span
                     iIsScrollDown=EFalse;
                   }
                  DrawNow();
                  break;
                }
             case EEikScrollThumbReleaseVert:
                  break;
             default:
                  break;
            }
        }

Usage:

// get an object of your scroll bar type
CEikScrollBar* sb = iSBFrame->VerticalScrollBar();

// it starts with 0 depicting your first scroll, every time you scroll your thumb position changes
// with number of scroll movement in one drag.
TInt pos=sb->ThumbPosition();