After second assign TPngImageCollectionItem object TreeView still paint first assigned image(Delphi XE 7)

Question

I use last TPngComponents "PngComponents for Delphi 2009 - Delphi 10.2 Tokyo". Create simple project to show my problem.

Why after the second assign TPngImageCollectionItem object TreeView still paint first assigned image and may be need call some refresh functions?

type
  TForm1 = class(TForm)
    pilTree: TPngImageList;
    pilNoImage: TPngImageList;
    pilAllCor: TPngImageList;
    tvCor: TTreeView;
    pilAllNotCor: TPngImageList;
    tvNoCor: TTreeView;
    procedure FormCreate(Sender: TObject);
  private
    { Private declarations }
  public
    { Public declarations }
  end;

procedure AddNodes(ATV: TTreeView);
var
  nFirst, nChild: TTreeNode;
begin
  nFirst := ATV.Items.AddChild(nil, '1');
  nChild := ATV.Items.AddChild(nFirst,'2');
  nChild.ImageIndex := 1;
  nChild.SelectedIndex := 1;
  nFirst.Expanded := True;
end;

procedure TForm1.FormCreate(Sender: TObject);
var
  iI: Integer;
  ItemAdd: TPngImageCollectionItem;
  ANode: TTreeNode;
begin
  // Steps working correct
  for iI := 0 to 1 do begin
    ItemAdd := pilAllCor.PngImages.Add;
    ItemAdd.Assign(pilTree.PngImages[iI]);
  end;
  // Steps working NOT correct
  for iI := 0 to 1 do begin
    ItemAdd := pilAllNotCor.PngImages.Add;
    ItemAdd.Assign(pilNoImage.PngImages[0]);
    ItemAdd.Assign(pilTree.PngImages[iI]);
  end;

  //Setup treeview
  tvCor.Images := pilAllCor;
  tvNoCor.Images := pilAllNotCor;
  AddNodes(tvCor);
  AddNodes(tvNoCor);
end;

Example:

Answer 1

The way to add a TPngImage to a TPngImageList is using AddPng and not fiddling around with the collection. This will also update the underlying Windows image list responsible for the actual display of the image.

The correct code should look like:

  for iI := 0 to 1 do begin
    pilAllCor.AddPng(pilTree.PngImages[iI].PngImage);
  end;

If you want to change an existing item you should assign the PngImage property of the collection item:

    pilAllCor.PngImages[iI].PngImage := pilTree.PngImages[iI].PngImage;