nameddatabase.cpp

Symbian文件数据库的实例源代码 很不错

CMyDBClass::~CMyDBClass()
{
	iItemsDatabase.Close();
	iFsSession.Close();
}
    
void CMyDBClass::ConstructL()
{
	User::LeaveIfError(iFsSession.Connect());
	
	TFileName DBFileName;
	// private path with no drive on it
	iFsSession.PrivatePath(DBFileName);
	
	TFindFile PrivFolder(iFsSession);
	// find out the drive
	if(KErrNone == PrivFolder.FindByDir(DBFileName, KNullDesC))
	{
		DBFileName.Copy(PrivFolder.File());
		DBFileName.Append(KtxDatabaseName);
				
		if(BaflUtils::FileExists(iFsSession, DBFileName))
		{
			User::LeaveIfError(iItemsDatabase.Open(iFsSession,
                                                                   DBFileName));
			ReadDbItemsL();
		}
		else
		{	// no database exists so we make one
			User::LeaveIfError(iItemsDatabase.Create(iFsSession,
                                                                   DBFileName));
			// and will create the onlt table needed for it
			CreateTableL(iItemsDatabase);
		}
	}
}
 
void CMyDBClass::CreateTableL(RDbDatabase& aDatabase) 
	{
	// Create a table definition
	CDbColSet* columns=CDbColSet::NewLC();
	
	// Add Columns
	TDbCol id(NCol0,EDbColInt32);
	// automatic indexing for items,it is our key field.
	id.iAttributes=id.EAutoIncrement;
	columns->AddL(id);				 
	
	columns->AddL(TDbCol(NCol1, EDbColText,100));
	columns->AddL(TDbCol(NCol2, EDbColText,100));
	
	// Create a table
	User::LeaveIfError(aDatabase.CreateTable(KtxtItemlist, *columns));
				
	// cleanup the column set
	CleanupStack::PopAndDestroy(columns);
}
 
void CMyDBClass::ReadDbItemsL(RArray<TExampleItem>& aItemArray)
{
	aItemArray.Reset();// first reset the array
	
	TFileName QueryBuffer;
	// just get all columns & rows
	QueryBuffer.Copy(_L("SELECT * FROM "));
	QueryBuffer.Append(KtxtItemlist);
	
	RDbView Myview;
	Myview.Prepare(iItemsDatabase,TDbQuery(QueryBuffer));
	CleanupClosePushL(Myview);
	Myview.EvaluateAll();
	Myview.FirstL();
 
	// Just delete one instance of the message
	while(Myview.AtRow()) 
	{	
		Myview.GetL();		
		
		TExampleItem NewItem;	
		NewItem.iIndex = Myview.ColInt(1);
        NewItem.iName.Copy(Myview.ColDes(2));
        NewItem.iValue.Copy(Myview.ColDes(3));
		
		aItemArray.Append(NewItem);		
		Myview.NextL();
	} 
	
	CleanupStack::PopAndDestroy(1); // Myview
}
 
void CMyDBClass::DeleteFromDatabaseL(TInt& aIndex)
{	
	TFileName QueryBuffer;
	QueryBuffer.Copy(_L("SELECT * FROM "));
	QueryBuffer.Append(KtxtItemlist);
	QueryBuffer.Append(_L(" WHERE "));
	QueryBuffer.Append(NCol0);
	QueryBuffer.Append(_L(" = "));
	QueryBuffer.AppendNum(aIndex);
		
	iItemsDatabase.Begin();
	
	RDbView Myview;
	// query buffr with index finds only the selected item row.
	Myview.Prepare(iItemsDatabase,TDbQuery(QueryBuffer));
	CleanupClosePushL(Myview);
	
	Myview.EvaluateAll();
	Myview.FirstL();
	// we have autoincrement in index so it should be unique
	// but just to make sure, we use 'while', instead of 'if'
	while(Myview.AtRow())            
	{	
		Myview.GetL();
		Myview.DeleteL();	
		Myview.NextL();
	}
			
	CleanupStack::PopAndDestroy(1); // Myview
	iItemsDatabase.Commit();
	// compacts the databse, by physicaly removig deleted data.
	iItemsDatabase.Compact();
}
 
void CMyDBClass::UpdateDatabaseL(const TDesC& aName, 
                                 const TDesC& aValue, 
                                          TInt& aIndex)
{	
	TFileName QueryBuffer;
	QueryBuffer.Copy(_L("SELECT * FROM "));
	QueryBuffer.Append(KtxtItemlist);
	QueryBuffer.Append(_L(" WHERE "));
	QueryBuffer.Append(NCol0);
	QueryBuffer.Append(_L(" = "));
	QueryBuffer.AppendNum(aIndex);
	
	iItemsDatabase.Begin();
	
	RDbView Myview;
	Myview.Prepare(iItemsDatabase, TDbQuery(QueryBuffer));
	CleanupClosePushL(Myview);
	
	Myview.EvaluateAll();
	Myview.FirstL();
	
	if(Myview.AtRow())            
	{			
		Myview.UpdateL();
		Myview.SetColL(2, aName);		
		Myview.SetColL(3, aValue);	
		Myview.PutL();
	}
			
	CleanupStack::PopAndDestroy(1); // Myview
	iItemsDatabase.Commit();
}
 
void CMyDBClass::SaveToDatabaseL(const TDesC& aName, 
                                 const TDesC& aValue, 
                                          TInt& aIndex)
{	
	TFileName QueryBuffer;
	QueryBuffer.Copy(_L("SELECT * FROM "));
	QueryBuffer.Append(KtxtItemlist);
 
	iItemsDatabase.Begin();
 
	RDbView Myview;
	Myview.Prepare(iItemsDatabase, TDbQuery(QueryBuffer));
	CleanupClosePushL(Myview);
 
	Myview.InsertL(); 
		
	Myview.SetColL(2, aName);
	Myview.SetColL(3, aValue);
 
	Myview.PutL();  
	
	aIndex = Myview.ColInt(1);// autoincrement gives us unique index.
			
	CleanupStack::PopAndDestroy(1); // Myview
	iItemsDatabase.Commit();
}