for i := 0 to cbb_controlmattype.Items.Count -1 do
  begin
     if cbb_controlmattype.Items[i].Selected = True then
     begin
        if cbb_controlmattype.Items[i].Expanded = False then
            cbb_controlmattype.Items[i].Expanded := True
        else
            cbb_controlmattype.Items[i].Expanded := False;
        mattypename := cbb_controlmattype.Items[i].Text;   //单击的时候临时赋值物料类别
        cbb_controlmattype.Items[i].Selected := False;    //避免小三角单击事件冲突
        Break;
     end;

end;