虚拟树Demos\Minimal 简单的例子

//分析虚拟树demo
6-VirtualTreeView\VirtualTreeViewV5.3.0\Demos\Minimal的main.pas文件

unit Main;

// Demonstration project for TVirtualStringTree to generally show how to get started.

// Written by Mike Lischke.

interface

uses

  Windows, Messages, SysUtils, Classes, Graphics, Controls, Forms, Dialogs,

  VirtualTrees, StdCtrls, ExtCtrls;

type

  TMainForm = class(TForm)

    VST: TVirtualStringTree;

    ClearButton: TButton;

    AddOneButton: TButton;

    Edit1: TEdit;

    Button1: TButton;

    Label1: TLabel;

    CloseButton: TButton;

    procedure FormCreate(Sender: TObject);

    procedure ClearButtonClick(Sender: TObject);

    procedure AddButtonClick(Sender: TObject);

    procedure VSTGetText(Sender: TBaseVirtualTree; Node: PVirtualNode; Column: TColumnIndex;

      TextType: TVSTTextType; var Text: UnicodeString);

    procedure VSTFreeNode(Sender: TBaseVirtualTree; Node: PVirtualNode);

    procedure VSTInitNode(Sender: TBaseVirtualTree; ParentNode, Node: PVirtualNode;

      var InitialStates: TVirtualNodeInitStates);

    procedure CloseButtonClick(Sender: TObject);

    procedure VSTStartDrag(Sender: TObject; var DragObject: TDragObject);

  end;

var

  MainForm: TMainForm;

//----------------------------------------------------------------------------------------------------------------------

implementation

{$R *.DFM}

type

  // This is a very simple record we use to store data in the nodes.

  // Since the application is responsible to manage all data including the node's caption

  // this record can be considered as minimal requirement in all VT applications.

  // Extend it to whatever your application needs.

  PMyRec = ^TMyRec;

  TMyRec = record

    Caption: WideString;

  end;

//----------------------------------------------------------------------------------------------------------------------

procedure TMainForm.FormCreate(Sender: TObject);

begin

  // We assign the OnGetText handler manually to keep the demo source code compatible

  // with older Delphi versions after using UnicodeString instead of WideString.

  VST.OnGetText := VSTGetText;

  // Let the tree know how much data space we need.

  VST.NodeDataSize := SizeOf(TMyRec); //设定一个node的内存大小，虚拟树的妙处

  // Set an initial number of nodes.

  VST.RootNodeCount := ;

end;

//----------------------------------------------------------------------------------------------------------------------

procedure TMainForm.ClearButtonClick(Sender: TObject);

var

  Start: Cardinal;

begin

  Screen.Cursor := crHourGlass;

  try

    Start := GetTickCount;

    VST.Clear;

    Label1.Caption := Format('Last operation duration: %d ms', [GetTickCount - Start]);

  finally

    Screen.Cursor := crDefault;

  end;

end;

//----------------------------------------------------------------------------------------------------------------------

procedure TMainForm.AddButtonClick(Sender: TObject);

var

  Count: Cardinal;

  Start: Cardinal;

begin

  // Add some nodes to the treeview.

  Screen.Cursor := crHourGlass;

  with VST do

  try

    Start := GetTickCount;

    case (Sender as TButton).Tag of

      : // add to root

        begin

          Count := StrToInt(Edit1.Text);

          RootNodeCount := RootNodeCount + Count;//自动改变这个属性即可

        end;

      : // add as child

        if Assigned(FocusedNode) then

        begin

          Count := StrToInt(Edit1.Text);

          ChildCount[FocusedNode] := ChildCount[FocusedNode] + Count;

          Expanded[FocusedNode] := True;

          InvalidateToBottom(FocusedNode);//要放到后面

        end;

    end;

    Label1.Caption := Format('Last operation duration: %d ms', [GetTickCount - Start]);

  finally

    Screen.Cursor := crDefault;

  end;

end;

//----------------------------------------------------------------------------------------------------------------------

procedure TMainForm.VSTGetText(Sender: TBaseVirtualTree; Node: PVirtualNode; Column: TColumnIndex;

  TextType: TVSTTextType; var Text: UnicodeString);

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.

  // OnGetText事件处理程序总是需要为它提供了树显示的字符串数据。

//注意,我们总是使用WideString。

  Data := Sender.GetNodeData(Node);//虚拟树的取值

  if Assigned(Data) then

    Text := Data.Caption;

end;

//----------------------------------------------------------------------------------------------------------------------

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.

  ///影响自由的字符串,VCL无法知道有一个但仍然需要自由。

  //为多个字段的记录必须释放使用Finalize(数据^)而不是单独触摸每一个成员。

  Finalize(Data^);

end;

//----------------------------------------------------------------------------------------------------------------------

procedure TMainForm.VSTInitNode(Sender: TBaseVirtualTree; ParentNode, Node: PVirtualNode;

  var InitialStates: TVirtualNodeInitStates);

var

  Data: PMyRec;

begin

  with Sender do

  begin

    Data := GetNodeData(Node);

    // Construct a node caption. This event is triggered once for each node but

    // appears asynchronously, which means when the node is displayed not when it is added.

    //构造一个节点标题。这个事件触发异步为每个节点,但一旦出现,这意味着当节点添加时不显示。  每次初始化时都会给这样的值

    Data.Caption := Format('Level %d, Index %d', [GetNodeLevel(Node), Node.Index]);

  end;

end;

//----------------------------------------------------------------------------------------------------------------------

procedure TMainForm.CloseButtonClick(Sender: TObject);

begin

  Close;

end;

//----------------------------------------------------------------------------------------------------------------------

procedure TMainForm.VSTStartDrag(Sender: TObject; var DragObject: TDragObject);

begin

  DragObject := TDragObject.Create;

end;

//----------------------------------------------------------------------------------------------------------------------

end.