TListview.items.clear long execution time

If you have a lot of items and are calling items.clear regualrly this may take significant cpu time and thus result in the lag. To fix this problem try a linear deletion of the items:

For X:=0 to listview1.items.count-1 do
         begin
          listview1.items.item[x].delete
         end;

Hope this solves your problem

Hypoviax

variant 1
// unhooking the renovation for time peelings - can enlarge speed

 ListView1.Items.BeginUpdate;
 ListView1.Items.clear;
 ListView1.Items.EndUpdate;

variant 2
//partial removing
 ListView1.Items.BeginUpdate;
For i:=0 to listview1.items.count-1 do
         begin
          listview1.items.item[0].delete;
          Application.ProcessMessages; //to did not hang
         end;
 ListView1.Items.EndUpdate;

>try-finaly-end
IMHO, spare!

>try-finaly-end
no need

my friend, if you don't use the try-finally, and if something goes wrong while clearing the ListView (e.g. you added Objects to your ListView and something goes wrong while freeing them, etc), you will never be able to see refreshes/updates to the listview till you restart your application... better be safe than sorry.  :-)

I agree . but when calling clear this unlikely.À at accompaniment in list or items[...].delete -  i agree :)

actually, I didn't notice that we posted the Begin/End-Update thingy only 1 minute (or seconds apart!)... ehhehe... lamtl354, if it works, give the points to 13_th, not me, ok? :-)

Adding large number of items to a list view cripples, even crashes your application. I would recommend using Virtual ListView (normal ListView with OwnerData = True) instead. See "Virtual ListView" example under Demos folder of Delphi (i.e. C:\Program Files\Borland\Delphi7\Demos\Virtual Listview). Or, you may use a third-party component:

http://www.delphi-gems.com/VirtualTreeview/VT.php