FMX.TListView (C++) - Sorting

Description

This example shows how to implement a sort function for FMX TListView items.

To test this example, create a new FireMonkey application and add a Delphi source unit to the C++ project to instantiate the generic class:

unit ImportUnitToInclude;
 
interface
uses
  System.Generics.Defaults,
  FMX.ListView.Appearances;
 
implementation
//force the generic/template to be generated by the Delphi compiler
var
   Comparer : TComparer<TListViewItem>;
end.

Delphi generics need to have an instantiation available in order for C++ to use them.

When using the Clang compiler, you can use use a lambda expression or a functor. The following code uses a lambda expression:

void SortListViewClangOnly(TListView *ListViewToSort)
{
  //using lambda expression for sorting
  ListViewToSort->Items->Sort(TComparer__1<TListViewItem*>::Construct([](TListViewItem* Left, TListViewItem* Right) -> int
  {
    return CompareText(Left->Text, Right->Text);
  } ));
}

If you are using a classic compiler, only the functor expression can be used:

void SortListViewClangAndClassic(TListView *ListViewToSort)
{
    //using a functor for sorting
    typedef  TComparison__1<TListViewItem*> TCompLVItem;
    struct TFmxLVSortCompare : public TCppInterfacedObject< TCompLVItem>
    {
         virtual int __fastcall Invoke(TListViewItem* Left, TListViewItem* Right)
        {
           return CompareText(Left->Text, Right->Text);
        };
    };
  ListViewToSort->Items->Sort(TComparer__1<TListViewItem*>::Construct(new TFmxLVSortCompare()));
}

To call one of the previous implementations, you can use the following code:

void __fastcall TForm2::Button4Click(TObject *Sender)
{
 SortListViewClangAndClassic(ListView1);
}

Or

 
void __fastcall TForm2::Button1Click(TObject *Sender)
{
  #ifdef __clang__
    SortListViewClangOnly(ListView1);
  #else
    ShowMessage(L"This is only for clang");
  #endif
}