TTreeNodes.BeginUpdate Method

Prevents the updating of the tree view until the EndUpdate method is called.

Pascal

procedure BeginUpdate;

C++

__fastcall BeginUpdate();

Description

BeginUpdate prevents the screen from being repainted when new nodes are added, deleted, or inserted. Tree nodes affected by the changes will have invalid Index values until EndUpdate is called.

Use BeginUpdate to prevent screen repaints and to speed processing time while adding nodes to the tree view.

Note: Calls to BeginUpdate are cumulative; for every call to BeginUpdate there must be a corresponding call to EndUpdate.

C++ Examples:

Copy Code

/*
The following example adds a new item to the selected item’s
list of child items in the tree view control. The new item
is added first in the list of child items. The new item is
identified by the text ‘New Item’. The TBitmap object is
attached to the new item.
*/
#include <memory>       //for STL auto_ptr class
Graphics::TBitmap *MyBitMap;

void __fastcall TForm1::Button1Click(TObject *Sender)
{
  static std::auto_ptr<Graphics::TBitmap> _MyBitMapCleaner((MyBitMap = new Graphics::TBitmap()));  // just create it once
  MyBitMap->LoadFromFile("..\\littleB.bmp");
  TreeView1->Items->BeginUpdate(); // keep the node from painting until it's built
  TreeView1->Items->AddChildObjectFirst(
    TreeView1->Selected, "New Item", MyBitMap);
  TreeView1->Items->EndUpdate();
}

Delphi Examples:

Copy Code

{
The following example adds a new item to the selected item’s
list of child items in the tree view control. The new item
is added first in the list of child items. The new item is
identified by the text ‘New Item’. The TBitmap object is
attached to the new item.
}
procedure TForm1.Button1Click(Sender: TObject);
var
  MyBitMap : TBitmap;
  node : TTreeNode;
begin
  MyBitMap := TBitmap.Create;
  MyBitMap.LoadFromFile('littleB.bmp');
  TreeView1.Items.BeginUpdate;
  node:= TreeView1.Items.AddChildObjectFirst(
    TreeView1.Selected, 'New Item', MyBitMap);
//  node.ImageIndex:= -1;
  TreeView1.Items.EndUpdate;
end;