Working with ChoiceList API - S60 Touch UI

Comments

21 Sep
2009

Article Review by User:FireSwarog (20090921)

Another useful example that demonstrates the new features of S60 5th. The article shows how you can use classes from ChoiceList API to provide user a choice from several alternatives.

The code snippet shows how to create a list to choose how to respond on the user's choice. You can realize own event handler with the help of observer pattern and interface MCoeControlObserver, such approach is very popular in Symbian C++. Furthermore, the author added a working demo project, which can be used for more detailed study of new opportunities for various kinds of experiments.

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28 Sep
2009

Article Review by savaj (20090928)

Apart from CAknPopupField, CAknChoiceList is considered as a alternative to drop-down list box of desktop system. As class CAknChoiceList is introduced in S60 5th edition, it is important to understand how to use CAknChoiceList efficiently. Article describes a way to implement CAknChoiceList and useful methods that can be used to enhance functionality of choice list. A working code example will be useful for more detailed study.

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Article Metadata

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Code Example

Source file: Media:ChoiceList.zip

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Article

Created: kiran10182 (02 Nov 2008)

Last edited: hamishwillee (08 Feb 2012)

Overview

ChoiceList API is a new component introduced in S60 5th edition Touch UI concept. In this article we will learn how to play with ChoiceList API with different methods.

What is ChoiceList API

• ChoiceList API is a new Touch UI component available with S60 5th Edition platform.
• In the construction of ChoiceList, you can define it with "default selection enabled" or "without selection enabled" for the items in the list.
• You can use Buttons as items on ChoiceList.
• You can fill the items of ChoiceList with array elements.
• ChoiceList API provides various function to manipulate items residing on ChoiceList.

Implementing ChoiceList component

ChoiceListAppView.h

• We will inherit our class from MCoeControlObserver interface and implement its pure virtual method HandleControlEventL() to receive and handle events for ChoiceList.
• Declare object of CAknChoiceList and use it to set observer for this class and handle events on ChoiceList.

...
...
#include <aknchoicelist.h>
 
// CLASS DECLARATION
class CChoiceListAppView : public CCoeControl, public MCoeControlObserver
	{
		.....
		.....
		//From MCoeControlObserver
		void HandleControlEventL(CCoeControl *aControl,TCoeEvent aEventType);
 
		//Application specific helper function
		void CreateChoiceListL();
 
		//From CCoeControl
		TInt CountComponentControls() const;
		CCoeControl* ComponentControl(TInt aIndex) const;
		.....
	private:
		CAknChoiceList* iChoiceList;
		....
	};

ChoiceListAppView.cpp

• Call to create choice list function from ConstructL() as shown below.

// -----------------------------------------------------------------------------
// CChoiceListAppView::ConstructL()
// Symbian 2nd phase constructor can leave.
// -----------------------------------------------------------------------------
//
void CChoiceListAppView::ConstructL(const TRect& aRect)
	{
	// Create a window for this application view
	CreateWindowL();
 
	CreateChoiceListL(); //We will create our choice list in this function
	....
	....
 
	// Set the windows size
	SetRect(aRect);
 
	// Activate the window, which makes it ready to be drawn
	ActivateL();
	}

• Create choice list and fill the default items from array.
• Set "this" as an observer for ChoiceList and eventually we will receive callbacks in HandleControlEventL()

void CChoiceListAppView::CreateChoiceListL()
	{
	CDesCArray* itemArray = new (ELeave) CDesCArrayFlat(5);
	CleanupStack::PushL(itemArray);
	itemArray->AppendL(_L("First"));
	itemArray->AppendL(_L("Second"));
	itemArray->AppendL(_L("Third"));
 
	iChoiceList = CAknChoiceList::NewL(this, itemArray);
	CleanupStack::Pop(itemArray);
	iChoiceList->SetContainerWindowL(*this);
	iChoiceList->SetObserver(this);
	iChoiceList->SetRect(TRect ( TPoint(100,200), TSize(120,10) ) );
	}

• We will handle callback events on choice list control as shown below in the HandleControlEventL

void CChoiceListAppView::HandleControlEventL(CCoeControl *aControl,TCoeEvent aEventType)
	{
	if(iChoiceList == aControl)
		switch(aEventType)
		{
			case EEventStateChanged:
			{
				TInt index = iChoiceList->SelectedIndex();
				_LIT(KMenuItem,"%d is selected");
				TBuf<20> buf;
				buf.Format(KMenuItem(), index+1);							
				CAknInformationNote* info = new (ELeave) CAknInformationNote;
				info->ExecuteLD(buf);
			}
			break;
		}
	}

• Definition for the following functions to return ChoiceList control.

TInt CChoiceListAppView::CountComponentControls() const
{
	return 1; // return number of controls inside this container
}
 
CCoeControl* CChoiceListAppView::ComponentControl(TInt aIndex) const
{
    switch ( aIndex )
    {
        case 0:
            return iChoiceList;
 
        default:
            return NULL;
    }
}

• Make sure to delete iChoiceList in the destructor of the class.

 
// -----------------------------------------------------------------------------
// CChoiceListAppView::~CChoiceListAppView()
// Destructor.
// -----------------------------------------------------------------------------
//
CChoiceListAppView::~CChoiceListAppView()
{
	....
	....
	if(iChoiceList)
	{
		delete iChoiceList;
		iChoiceList = NULL;
	}
}

Useful functions

CAknChoiceList

• SelectedIndex()
• AddItemL()
• RemoveItem()
• HideChoiceList()
• InsertItemL()

MCoeControlObserver

• HandleControlEventL()

Keywords

Headers

• #include <aknchoicelist.h>

Classes

• CAknChoiceList
• MCoeControlObserver

Libraries

• eikcoctl.lib

Example Application

• ChoiceList.zip

Related links

• A tour to the S60 Touch UI components
• Working with Toolbar API - S60 Touch UI
• Working with LongTapDetector API - S60 Touch UI
• Working with Stylus Pop-up Menu API - S60 Touch UI
• Working with Tactile Feedback Client API - S60 Touch UI
• Working with Adaptive Search feature - S60 Touch UI
• Working with Generic Button API - S60 Touch UI
• Working with SingleStyleTreeList with Hierarchical Lists API - S60 Touch UI
• Working with SingleColumnStyleTreeList with Hierarchical Lists API - S60 Touch UI

Reference list

• S60 5th edition SDK help
• S60 5th Edition C++ Developer's Library v1.0