Items in QListView should sort on Header Click

[vinnu]

hai

OK...let me say my way of implementation....
i have written the connect stmt to the header click.

QHeader * pHeader = m_pBBListView->header();
connect(pHeader,SIGNAL(clicked(int)),this, SLOT(sortColumns(int)));

QHeader * pHeader = m_pBBListView->header();
connect(pHeader,SIGNAL(clicked(int)),this, SLOT(sortColumns(int)));

To copy to clipboard, switch view to plain text mode 

in Sortcolumn() i have added the following functionality.

void BBPickerDialog::sortColumns(int index)
{
   BBPtr<BBStruct>listViewItemStruct(BBStruct::create("Item", "Item"));//it is our struct where we handle the our list view items//
 
	QListViewItemIterator it( m_pBBListView );//m_pBBListview is member of BBpicker Dialog.
	int valueIndex = (index == 0)?1:0;
 
	PChar tempStr,tempStr2;
 
    for ( ; it.current(); ++it)
	{
		QListViewItem  *pItem = it.current();
		QString key = pItem->text(index);
		QString value = pItem->text(valueIndex);
		sortList->addCopy(key.latin1());
		listViewItemStruct->addStringField(key.latin1(),value);
	}
	for(size_t i=0;i<sortList->size();i++)
	{
		for(size_t j = i+1 ;j <sortList->size()-1;j++)
		{
			if(strcmp((*sortList)[i],(*sortList)[j])>0)
			{
				tempStr  = strDup((*sortList)[i]);
				tempStr2 = strDup((*sortList)[j]);
				sortList->replaceItemAtIndex(i,tempStr2);
				sortList->replaceItemAtIndex(j,tempStr);
			}
		}
	}
	QListViewItem *pLastItem = NULL;
	m_pBBListView->clear();
 
	for(size_t indx=0;indx<sortList->size();indx++)
	{
		BBPtr<BBString> value(listViewItemStruct->getStringField((*sortList)[indx]));
		if(index==0)
			pLastItem =	new QListViewItem( m_pBBListView,(*sortList)[indx],value->asPChar());
		else
			pLastItem = new QListViewItem( m_pBBListView,value->asPChar(),(*sortList)[indx]);
	}
}

void BBPickerDialog::sortColumns(int index)
{
   BBPtr<BBStruct>listViewItemStruct(BBStruct::create("Item", "Item"));//it is our struct where we handle the our list view items//

	QListViewItemIterator it( m_pBBListView );//m_pBBListview is member of BBpicker Dialog.
	int valueIndex = (index == 0)?1:0;

	PChar tempStr,tempStr2;

    for ( ; it.current(); ++it)
	{
		QListViewItem  *pItem = it.current();
		QString key = pItem->text(index);
		QString value = pItem->text(valueIndex);
		sortList->addCopy(key.latin1());
		listViewItemStruct->addStringField(key.latin1(),value);
	}
	for(size_t i=0;i<sortList->size();i++)
	{
		for(size_t j = i+1 ;j <sortList->size()-1;j++)
		{
			if(strcmp((*sortList)[i],(*sortList)[j])>0)
			{
				tempStr  = strDup((*sortList)[i]);
				tempStr2 = strDup((*sortList)[j]);
				sortList->replaceItemAtIndex(i,tempStr2);
				sortList->replaceItemAtIndex(j,tempStr);
			}
		}
	}
	QListViewItem *pLastItem = NULL;
	m_pBBListView->clear();

	for(size_t indx=0;indx<sortList->size();indx++)
	{
		BBPtr<BBString> value(listViewItemStruct->getStringField((*sortList)[indx]));
		if(index==0)
			pLastItem =	new QListViewItem( m_pBBListView,(*sortList)[indx],value->asPChar());
		else
			pLastItem = new QListViewItem( m_pBBListView,value->asPChar(),(*sortList)[indx]);
	}
}

To copy to clipboard, switch view to plain text mode 

u can understand my code ...

i think now u can understand my problem

[jacek]

u can understand my code ...

Unreadable code is a bad code.

First let's see how many lines of code it would take to implement it using QListViewItem::compare():

int CustomListViewItem::compare( QListViewItem * item, int col, bool ascending ) const
{
   Q_UNUSED( ascending ); // ignored, like the docs recommend
   if( col == 0 ) {
      int a = text( col ).toInt();
      int b = item->text( col ).toInt();
      return (a - b);
   }
   else {
      return QString::localeAwareCompare( text( col ), item->text( col ) );
   }
}

int CustomListViewItem::compare( QListViewItem * item, int col, bool ascending ) const
{
   Q_UNUSED( ascending ); // ignored, like the docs recommend
   if( col == 0 ) {
      int a = text( col ).toInt();
      int b = item->text( col ).toInt();
      return (a - b);
   }
   else {
      return QString::localeAwareCompare( text( col ), item->text( col ) );
   }
}

To copy to clipboard, switch view to plain text mode 

See? It wasn't that hard.

Now for the sortColumns(). First of all you use QString::latin1(). What will happen with non-ASCII characters? And why do you delete all items, if you just need to reorder them? Why don't you reuse existing code?

I would do it this way:

class NumericalComparator
{
   public:
     NumericalComparator( int column ) : _column( column ) {}
 
     bool operator()( const QListViewItem *a, const QListViewItem *b ) const
     {
         return ( ( a->text( _column ).toInt() - b->text( _column ).toInt() ) > 0 );
     }
 
  private:
     int _column;
};
 
class StringComparator
{
   public:
     StringComparator( int column ) : _column( column ) {}
 
     bool operator()( const QListViewItem *a, const QListViewItem *b ) const
     {
         return ( QString::localeAwareCompare( a->text( _column ), b->text( _column ) ) > 0 );
     }
 
  private:
     int _column;
};
 
void BBPickerDialog::sortColumns(int index)
{
   m_pBBListView->setUpdatesEnabled( false );
 
   std::vector< QListViewItem * > items( m_pBBListView->childCount() );
 
   for( QListViewItemIterator it( m_pBBListView ); it.current(); ++it ) {
      items.push_back( it.current() );
   }
 
   if( index == 0 ) {
      std::sort( items.begin(), items.end(), NumericalComparator( index ) );
   }
   else {
      std::sort( items.begin(), items.end(), StringComparator( index ) );
   }
 
   for( std::vector< QListViewItem *>::iterator it = items.begin(); it != items.end(); ++it ) {
      m_pBBListView->takeItem( *it );
      m_pBBListView->insertItem( *it );
   }
 
   m_pBBListView->setUpdatesEnabled( true );
}

class NumericalComparator
{
   public:
     NumericalComparator( int column ) : _column( column ) {}

     bool operator()( const QListViewItem *a, const QListViewItem *b ) const
     {
         return ( ( a->text( _column ).toInt() - b->text( _column ).toInt() ) > 0 );
     }

  private:
     int _column;
};

class StringComparator
{
   public:
     StringComparator( int column ) : _column( column ) {}

     bool operator()( const QListViewItem *a, const QListViewItem *b ) const
     {
         return ( QString::localeAwareCompare( a->text( _column ), b->text( _column ) ) > 0 );
     }

  private:
     int _column;
};

void BBPickerDialog::sortColumns(int index)
{
   m_pBBListView->setUpdatesEnabled( false );

   std::vector< QListViewItem * > items( m_pBBListView->childCount() );

   for( QListViewItemIterator it( m_pBBListView ); it.current(); ++it ) {
      items.push_back( it.current() );
   }

   if( index == 0 ) {
      std::sort( items.begin(), items.end(), NumericalComparator( index ) );
   }
   else {
      std::sort( items.begin(), items.end(), StringComparator( index ) );
   }

   for( std::vector< QListViewItem *>::iterator it = items.begin(); it != items.end(); ++it ) {
      m_pBBListView->takeItem( *it );
      m_pBBListView->insertItem( *it );
   }

   m_pBBListView->setUpdatesEnabled( true );
}

To copy to clipboard, switch view to plain text mode 

Now (provided that this code works, as I didn't test it) you can see that you don't need to copy anything, except for the pointers, and that you can easily reuse existing code (in this case from STL).

If you don't like STL, you can do a similar thing using QPtrList --- just subclass QPtrList<QListViewItem> and reimplement compareItems().

[vinnu]

Hai

Thank u .i will put it in my code and see whether it works or not and come to u again..

thanks a lot jaeck.

vinnu

[vinnu]

Hai jacek,

Thank u for ur help in time.I have approached my clients and said the problem and i have got the green signal to derive a class from QListviewItem and overide compare.It worked for me .

Thank u so much

bye
vinnu