delphi - 在 VirtualTreeView 中编辑根节点单元格文本

Question

我想更改现有虚拟(根)节点的单元格文本。我可以更改数据，但我必须刷新整个 TreeView，以便再次触发 GetText。是否有更简单的方法或可能的方法来仅刷新 1 个根节点而不是整个树？

感谢您的帮助。

Answer 1

在下面的代码中，我尝试模拟您的节点更新事件。这里用按钮点击Button1Click事件来表示。在这里，如果您单击该按钮，数据记录中的值将增加，并且节点将被强制重新绘制(这将触发 OnGetText 事件，您将在该记录中获得新增加的值准备好获取)。在您的实际代码中，您需要执行以下操作:

• 找到您要更新的节点(我找到了 TopNode :-)
• 更新该节点的数据记录(在我的情况下，Count 值会递增)
• 调用该节点的 InvalidateNode(这将触发某些事件的虚拟事件链，但 OnGetText 将在其中)

type
  PTreeData = ^TTreeData;
  TTreeData = record
    Title: string;
    Count: Integer;
  end;

procedure TForm1.FormCreate(Sender: TObject);
var
  TreeData: PTreeData;
  TreeNode: PVirtualNode;
begin
  // this is just for memory leaks report
  ReportMemoryLeaksOnShutdown := True;
  // initialize data size for our data record
  VirtualTree.NodeDataSize := SizeOf(TTreeData);
  // add one node and store it to the TreeNode variable
  TreeNode := VirtualTree.AddChild(nil);
  // get the pointer to just created node data record
  TreeData := VirtualTree.GetNodeData(TreeNode);
  // and assign some values to that data record
  TreeData.Title := 'Count: ';
  TreeData.Count := 0;
end;

procedure TForm1.Button1Click(Sender: TObject);
var
  TreeData: PTreeData;
  TreeNode: PVirtualNode;
begin
  // now I take the the top node just as an example
  TreeNode := VirtualTree.TopNode;
  // get the pointer to its data record
  TreeData := VirtualTree.GetNodeData(TreeNode);
  // increase the value in data record for this node
  TreeData.Count := TreeData.Count + 1;
  // and force the node to repaint, what will except
  // other events trigger also the OnGetText one
  VirtualTree.InvalidateNode(TreeNode);
end;

procedure TForm1.VirtualTreeGetText(Sender: TBaseVirtualTree;
  Node: PVirtualNode; Column: TColumnIndex; TextType: TVSTTextType;
  var CellText: string);
var
  TreeData: PTreeData;
begin
  // here I'll get the pointer to data of the currently refreshed cell's node
  TreeData := VirtualTree.GetNodeData(Node);
  // and return the caption of the cell
  CellText := TreeData.Title + IntToStr(TreeData.Count);
end;

procedure TForm1.VirtualTreeFreeNode(Sender: TBaseVirtualTree;
  Node: PVirtualNode);
var
  TreeData: PTreeData;
begin
  // this is here because of VT memory leaks, so get the pointer to data
  TreeData := Sender.GetNodeData(Node);
  // and finalize them
  Finalize(TreeData^);
end;