TVirtualStringTree的Minimal例子学习

预步骤第一步，定义数据结构
type
PMyRec = ^TMyRec;
TMyRec = record
Caption: WideString;
end;
预步骤第二步，规定取得节点数据时候的大小
procedure TMainForm.FormCreate(Sender: TObject);
begin
VST.NodeDataSize := SizeOf(TMyRec); // 如果没用到数据，貌似屏蔽也没关系
// VST.RootNodeCount := 20; // 可以尝试指定节点数据
end;

第一步，初始化节点的内容（赋值）：
procedure TMainForm.VSTInitNode(Sender: TBaseVirtualTree; ParentNode, Node: PVirtualNode;
var InitialStates: TVirtualNodeInitStates);
var
Data: PMyRec;
begin
with Sender do
begin
Data := GetNodeData(Node); // 只是取得当前节点的指针而已，其内容仍需程序员处理
// 建立每个节点的数据，注意每个节点只触发一次。
// 为数据赋值，一次赋值，永远拥有。而不是每次重复赋值。异步显示刚增加的数据
Data.Caption := Format('Level %d, Index %d', [GetNodeLevel(Node), Node.Index]);
end;
end;

第二步，定义某个GetText函数，用来自动随时取得某个节点的数据：
procedure TMainForm.VSTGetText(Sender: TBaseVirtualTree; Node: PVirtualNode;
Column: TColumnIndex; TextType: TVSTTextType; var CellText: string);
var
Data: PMyRec;
begin
// A handler for the OnGetText event is always needed as it provides the tree with the string data to display.
// Note that we are always using WideString.
Data := Sender.GetNodeData(Node);
if Assigned(Data) then Text := Data.Caption; // 这句非必要，是在写窗口的Caption，但很好的演示了取到数据以后可以做很多事情
end;

第三步，增加根节点，或者子节点。或者清除所有节点：VST.Clear;
procedure TMainForm.AddButtonClick(Sender: TObject);
var
Start: Cardinal;
begin
with VST do
begin
Start := GetTickCount; // 计算时间
case (Sender as TButton).Tag of
0: // add to root
begin
RootNodeCount := 10; // 就这一句就足够增加节点了
end;
1: // add as child
if Assigned(FocusedNode) then
begin
ChildCount[FocusedNode] := ChildCount[FocusedNode] + 2; // ChildCount 和 FocusedNode 都是自带属性
Expanded[FocusedNode] := True; // 自带展开方法
InvalidateToBottom(FocusedNode); // 自带全部刷新
end;
end;
// 速度快啊，10万个节点32ms. 100万个节点200ms左右，1000万个节点40秒（内存不够，硬盘狂闪）
// Label1.Caption := Format('Last operation duration: %d ms', [GetTickCount - Start]);
end;
end;

最后，释放节点：
procedure TMainForm.VSTFreeNode(Sender: TBaseVirtualTree; Node: PVirtualNode);
var
Data: PMyRec;
begin
Data := Sender.GetNodeData(Node);
// Explicitely free the string, the VCL cannot know that there is one but needs to free
// it nonetheless. For more fields in such a record which must be freed use Finalize(Data^) instead touching
// every member individually.
Finalize(Data^);
end;

TVirtualNode = packed record
Index, // index of node with regard to its parent
ChildCount: Cardinal; // number of child nodes
NodeHeight: Word; // height in pixels
States: TVirtualNodeStates; // states describing various properties of the node (expanded, initialized etc.)
Align: Byte; // line/button alignment
CheckState: TCheckState; // indicates the current check state (e.g. checked, pressed etc.)
CheckType: TCheckType; // indicates which check type shall be used for this node
Dummy: Byte; // dummy value to fill DWORD boundary
TotalCount, // sum of this node, all of its child nodes and their child nodes etc.
TotalHeight: Cardinal; // height in pixels this node covers on screen including the height of all of its
// children
// Note: Some copy routines require that all pointers (as well as the data area) in a node are
// located at the end of the node! Hence if you want to add new member fields (except pointers to internal
// data) then put them before field Parent.
Parent, // reference to the node's parent (for the root this contains the treeview)
PrevSibling, // link to the node's previous sibling or nil if it is the first node
NextSibling, // link to the node's next sibling or nil if it is the last node
FirstChild, // link to the node's first child...
LastChild: PVirtualNode; // link to the node's last child...
Data: record end; // this is a placeholder, each node gets extra data determined by NodeDataSize
end;