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Listview and Imagelist item deletion

ray_marik
ray_marik asked
on
I have a listview and and imagelist on my form, the listview is set to display large icons from left to right. The problem is that I want to set  a limit on how many items the listview can display at a time, say 10. I want to just pass a bitmap to this listview procedure, and it can internally add it and delete the first one if the total number of icons is already 10. This procedure works well up to 11, but then it starts adding icons not to the end of the listview but the beginning in increasing numbers. I've tried everything but can't seem to get it right.

procedure TForm1.FormCreate(Sender: TObject);
begin
  ImageList1.Height := 200;
  ImageList1.Width := 200;
  // initialize LV
  ListView1.Left := 8;
  ListView1.Top := 12;
  ListView1.Height := 244;
  ListView1.Width := 445;
  ListView1.Color := clActiveCaption;
  ListView1.ColumnClick := False;
  ListView1.IconOptions.Arrangement := iaLeft;
  ListView1.ShowColumnHeaders := False;

  ListView1.LargeImages := ImageList1;
  ListView1.LargeImages.Height := 200;
  ListView1.LargeImages.Width := 200;
end;

procedure TForm1.Button1Click(Sender: TObject);
var
  bmp: TBitmap;
begin
  OpenDialog1.Filter := 'Bitmaps (*.bmp)|*.BMP';
  if OpenDialog1.Execute then
  begin
    if OpenDialog1.FileName <> '' then
    begin
      bmp := TBitmap.Create;
      try
        bmp.LoadFromFile(OpenDialog1.FileName);
        pushOntoListView(ImageList1, ListView1, bmp, OpenDialog1.FileName);
      finally
        bmp.Free;
      end;

    end;
  end;
end;

procedure pushOntoListView(IL: TImageList; LV: TListView; bmp: TBitmap; inputStr: String);
const
  Max_Count = 10;
var
  index: integer;
  ListItem: TListItem;
begin
  if LV.Items.Count >= Max_Count then
  begin
    //IL.Delete(0);
    LV.Items.Delete(0);
  end;

  // load bitmap into ImageList
  index := IL.Add(bmp, nil);
  // load ImageList into ListView
  if index > -1 then
  begin
    with LV do
    begin
      ListItem := Items.Add;
      Listitem.Caption := inputStr;
      ListItem.ImageIndex := index;
    end;
  end;
end;
Comment
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Software architect
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Top Expert 2012
Commented:
your procedure may looks like (hint: do arrange after delete):

procedure pushOntoListView(IL: TImageList; LV: TListView; bmp: TBitmap; inputStr: String);
const
  Max_Count = 10;
var
  index: integer;
  ListItem: TListItem;
begin
  LV.Items.BeginUpdate;
  try
    if LV.Items.Count >= Max_Count then
    begin
      LV.Items.Delete(0);
      LV.Arrange(arAlignLeft);
    end;

    // load bitmap into ImageList
    index := IL.Add(bmp, nil);
    // load ImageList into ListView
    if index > -1 then
    begin
      with LV do
      begin
        ListItem := Items.Add;
        Listitem.Caption := inputStr;
        ListItem.ImageIndex := index;
      end;
    end;
  finally
    LV.Items.EndUpdate;
  end;
end;

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... another note: you can use custom sort to rearrange items.
Ephraim WangoyaSoftware Engineer
CERTIFIED EXPERT

Commented:
try

procedure pushOntoListView(IL: TImageList; LV: TListView; bmp: TBitmap; inputStr: String);
const
  Max_Count = 10;
var
  index: integer;
  ListItem: TListItem;
begin
  LV.Items.BeginUpdate;
  try
    if LV.Items.Count >= Max_Count then
    begin
      //IL.Delete(0);
      LV.Items.Delete(0);
    end;

    // load bitmap into ImageList
    index := IL.Add(bmp, nil);
    // load ImageList into ListView
    if index > -1 then
    begin
      ListItem := LV.Items.Add;
      Listitem.Caption := inputStr;
      ListItem.ImageIndex := index;
    end;
  finally
    LV.Items.EndUpdate;
  end;
end;

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Author

Commented:
Thank you both for your solutions.
However, it seems specifying "LV.Arrange(arAlignLeft)" is the key which is why I rewarded sinisav.