ListBox.Items.Add is slow and flickers (Views: 27)
Problem/Question/Abstract: ListBox.Items.Add is slow and flickers Answer: Adding a (larger) group of entries to a ListBox is very slow, because after every "items.add" call the ListBox is repainted. There are two ways to overcome this: Use the Windows message WM_SETREDRAW (see Win32.hlp for details). The VCL provides two methods for this: BeginUpdate and EndUpdate. I would assume that this is faster than solve #2. Read the strings in a temporary TStringList object. Maybe you already have such a list - in this case you should use your existing list. Then use the Assign method to transfer the whole list. Solve 1: procedure TForm1.Button1Click(Sender: TObject); var i: integer; begin ListBox1.Items.BeginUpdate; for i := 1 to maxitems do ListBox1.Items.add(IntToStr(i)); ListBox1.Items.EndUpate; end; Solve 2: procedure TForm1.Button2Click(Sender: TObject); var i: integer; tmp: tstringlist; begin tmp := TStringList.Create; for i := 1 to maxitems do tmp.add(inttostr(i)); ListBox1.Items.Assign(tmp); tmp.Free; end; |