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delphi – 是否可以将VirtualStringTree用于主细节网格视图？

发布时间：2020-12-15 04:01:00 所属栏目：大数据 来源：网络整理
导读：好吧,我在这里得到了一些非常棘手的东西…… 我想将标题绘制/使用到ChildNode. 我认为这个想法是合理的,因为在子节点中有标题会让人看起来很棒,所以可以在表格中指定子节点. 是否有VST具有或根本不可能的功能？ 谢谢你的帮助. 解决方法 1.有没有办法将Virtua
好吧,我在这里得到了一些非常棘手的东西……
我想将标题绘制/使用到ChildNode.
我认为这个想法是合理的,因为在子节点中有标题会让人看起来很棒,所以可以在表格中指定子节点.
是否有VST具有或根本不可能的功能？

谢谢你的帮助.

解决方法

1.有没有办法将VirtualTreeView用于主/详细网格视图？

不,目前没有这样的功能可用,恕我直言不会,因为这将涉及对现有代码的非常大的干预.

2.如何为子节点详细信息网格视图创建功能完整的标头？

考虑到几种方法,如何模拟子节点的头部外观和行为,我发现对于详细网格视图使用嵌套树视图很有用.这为您提供了详细数据的独立性,并允许您将嵌套树视图定位到子节点矩形的整个模拟最小化.

2.1.启动项目

在下面的项目中,我试图展示如何实现这样一个简单的任务,例如在子节点内部定位控件可能是(不涉及原始的VirtualTree代码).把它作为一个启动项目,而不是最终的解决方案.

2.2.已知问题&局限性：

>这个项目是经过编写和测试的,每个根节点只使用一个子节点,所以当你超过这个限制时不要对行为感到惊讶,因为这个设计没有设计,甚至没有测试过
>当主树的双击列大小调整为列调整大小时,当ScrollDC函数滚动画布时,嵌套的树视图会用线条透支
>保持VirtualTree代码而不改变我已经覆盖了滚动条更新的方法.每当需要更新滚动条时,它用于更新嵌套的树视图边界
>当前OnExpanded实现在范围和滚动位置固定之前触发事件,是什么使代码更复杂并且有一个很大的弱点 – 在显示树之后更新细节树视图的边界,有时可以看到什么

2.3.项目代码

它是在Delphi 2009中编写和测试的,用于Delphi 7.用于下一个代码follow this link的注释版本：

Unit1.pas

unit Unit1;

interface

uses
  Windows,Messages,SysUtils,Variants,Classes,Graphics,Controls,Forms,Dialogs,StdCtrls,VirtualTrees;

type
  TVTScrollBarsUpdateEvent = procedure(Sender: TBaseVirtualTree; DoRepaint: Boolean) of object;
  TVirtualStringTree = class(VirtualTrees.TVirtualStringTree)
  private
    FOnUpdateScrollBars: TVTScrollBarsUpdateEvent;
  public
    procedure UpdateScrollBars(DoRepaint: Boolean); override;
  published
    property OnUpdateScrollBars: TVTScrollBarsUpdateEvent read FOnUpdateScrollBars write FOnUpdateScrollBars;
  end;

type
  PNodeSubTree = ^TNodeSubTree;
  TNodeSubTree = class
    FChildTree: TVirtualStringTree;
  end;

type
  TForm1 = class(TForm)
    Button1: TButton;
    VirtualStringTree1: TVirtualStringTree;
    procedure FormCreate(Sender: TObject);
    procedure Button1Click(Sender: TObject);
    procedure VirtualStringTree1AfterAutoFitColumns(Sender: TVTHeader);
    procedure VirtualStringTree1BeforeDrawTreeLine(Sender: TBaseVirtualTree;
      Node: PVirtualNode; Level: Integer; var PosX: Integer);
    procedure VirtualStringTree1Collapsed(Sender: TBaseVirtualTree;
      Node: PVirtualNode);
    procedure VirtualStringTree1ColumnResize(Sender: TVTHeader;
      Column: TColumnIndex);
    procedure VirtualStringTree1Expanded(Sender: TBaseVirtualTree;
      Node: PVirtualNode);
    procedure VirtualStringTree1FocusChanging(Sender: TBaseVirtualTree; OldNode,NewNode: PVirtualNode; OldColumn,NewColumn: TColumnIndex;
      var Allowed: Boolean);
    procedure VirtualStringTree1FreeNode(Sender: TBaseVirtualTree;
      Node: PVirtualNode);
    procedure VirtualStringTree1MeasureItem(Sender: TBaseVirtualTree;
      TargetCanvas: TCanvas; Node: PVirtualNode; var NodeHeight: Integer);
  private
    procedure InvalidateSubTrees(Tree: TBaseVirtualTree);
    procedure ResizeSubTrees(Tree: TBaseVirtualTree);
    procedure UpdateSubTreeBounds(Tree: TBaseVirtualTree; Node: PVirtualNode);
    procedure OnUpdateScrollBars(Sender: TBaseVirtualTree; DoRepaint: Boolean);
  public
    { Public declarations }
  end;

var
  Form1: TForm1;

implementation

{$R *.dfm}

{ TVirtualStringTree }

procedure TVirtualStringTree.UpdateScrollBars(DoRepaint: Boolean);
begin
  inherited;
  if HandleAllocated and Assigned(FOnUpdateScrollBars) then
    FOnUpdateScrollBars(Self,DoRepaint);
end;

{ TForm1 }

procedure TForm1.FormCreate(Sender: TObject);
begin
  ReportMemoryLeaksOnShutdown := True;
  VirtualStringTree1.NodeDataSize := SizeOf(TNodeSubTree);
  VirtualStringTree1.OnUpdateScrollBars := OnUpdateScrollBars;
end;

procedure TForm1.Button1Click(Sender: TObject);
var
  Data: PNodeSubTree;
  Node: PVirtualNode;
begin
  Node := VirtualStringTree1.AddChild(nil);
  Node := VirtualStringTree1.AddChild(Node);
  VirtualStringTree1.InitNode(Node);
  Data := VirtualStringTree1.GetNodeData(Node);
  Data^ := TNodeSubTree.Create;
  Data^.FChildTree := TVirtualStringTree.Create(nil);
  with Data.FChildTree do
  begin
    Visible := False;
    Parent := VirtualStringTree1;
    Height := 150;
    DefaultNodeHeight := 21;
    Header.AutoSizeIndex := 0;
    Header.Font.Charset := DEFAULT_CHARSET;
    Header.Font.Color := clWindowText;
    Header.Font.Height := -11;
    Header.Font.Name := 'Tahoma';
    Header.Font.Style := [];
    Header.Height := 21;
    Header.Options := [hoColumnResize,hoDrag,hoShowSortGlyphs,hoVisible];
    TabStop := False;
    with Header.Columns.Add do
    begin
      Width := 100;
      Text := 'Header item 1';
    end;
    with Header.Columns.Add do
    begin
      Width := 100;
      Text := 'Header item 2';
    end;
  end;
end;

procedure TForm1.VirtualStringTree1AfterAutoFitColumns(Sender: TVTHeader);
begin
  InvalidateSubTrees(Sender.Treeview);
end;

procedure TForm1.VirtualStringTree1BeforeDrawTreeLine(Sender: TBaseVirtualTree;
  Node: PVirtualNode; Level: Integer; var PosX: Integer);
begin
  if Level = 1 then
    PosX := 0;
end;

procedure TForm1.VirtualStringTree1Collapsed(Sender: TBaseVirtualTree;
  Node: PVirtualNode);
var
  Data: PNodeSubTree;
begin
  Data := VirtualStringTree1.GetNodeData(Node.FirstChild);
  if Assigned(Data^) and Assigned(Data^.FChildTree) then
    Data^.FChildTree.Visible := False;
end;

procedure TForm1.VirtualStringTree1ColumnResize(Sender: TVTHeader;
  Column: TColumnIndex);
begin
  ResizeSubTrees(Sender.Treeview);
end;

procedure TForm1.VirtualStringTree1Expanded(Sender: TBaseVirtualTree;
  Node: PVirtualNode);
var
  Data: PNodeSubTree;
begin
  Data := VirtualStringTree1.GetNodeData(Node.FirstChild);
  if Assigned(Data^) and Assigned(Data^.FChildTree) then
    Data^.FChildTree.Visible := True;
end;

procedure TForm1.VirtualStringTree1FocusChanging(Sender: TBaseVirtualTree;
  OldNode,NewColumn: TColumnIndex;
  var Allowed: Boolean);
begin
  if Sender.GetNodeLevel(NewNode) = 1 then
  begin
    Allowed := False;
    if Sender.AbsoluteIndex(OldNode) > Sender.AbsoluteIndex(NewNode) then
      Sender.FocusedNode := Sender.GetPreviousSibling(OldNode)
    else
    if OldNode <> Sender.GetLastChild(nil) then
      Sender.FocusedNode := Sender.GetNextSibling(OldNode)
    else
      Sender.FocusedNode := OldNode;
  end;
end;

procedure TForm1.VirtualStringTree1FreeNode(Sender: TBaseVirtualTree;
  Node: PVirtualNode);
var
  Data: PNodeSubTree;
begin
  Data := VirtualStringTree1.GetNodeData(Node);
  if Assigned(Data^) then
  begin
    if Assigned(Data^.FChildTree) then
      Data^.FChildTree.Free;
    Data^.Free;
  end;
end;

procedure TForm1.VirtualStringTree1MeasureItem(Sender: TBaseVirtualTree;
  TargetCanvas: TCanvas; Node: PVirtualNode; var NodeHeight: Integer);
var
  Data: PNodeSubTree;
begin
  if VirtualStringTree1.GetNodeLevel(Node) = 1 then
  begin
    Data := VirtualStringTree1.GetNodeData(Node);
    if Assigned(Data^) and Assigned(Data^.FChildTree) then
      NodeHeight := Data^.FChildTree.Height + 8;
  end;
end;

procedure TForm1.InvalidateSubTrees(Tree: TBaseVirtualTree);
var
  Data: PNodeSubTree;
  Node: PVirtualNode;
begin
  Node := Tree.GetFirst;
  while Assigned(Node) do
  begin
    if Tree.HasChildren[Node] then
    begin
      Data := Tree.GetNodeData(Node.FirstChild);
      if Assigned(Data^) and Assigned(Data^.FChildTree) then
      begin
        Data^.FChildTree.Header.Invalidate(nil);
        Data^.FChildTree.Invalidate;
      end;
    end;
    Node := Tree.GetNextSibling(Node);
  end;
end;

procedure TForm1.ResizeSubTrees(Tree: TBaseVirtualTree);
var
  Node: PVirtualNode;
begin
  Node := Tree.GetFirst;
  while Assigned(Node) do
  begin
    if Tree.HasChildren[Node] then
      UpdateSubTreeBounds(Tree,Node.FirstChild);
    Node := Tree.GetNextSibling(Node);
  end;
end;

procedure TForm1.UpdateSubTreeBounds(Tree: TBaseVirtualTree; Node: PVirtualNode);
var
  R: TRect;
  Data: PNodeSubTree;
begin
  if Assigned(Node) then
  begin
    Data := Tree.GetNodeData(Node);
    if Assigned(Data^) and Assigned(Data^.FChildTree) and
      Data^.FChildTree.Visible then
    begin
      R := Tree.GetDisplayRect(Node,-1,False,True);
      R.Left := R.Left + (Tree as TVirtualStringTree).Indent;
      R.Top := R.Top + 4;
      R.Right := R.Right - 8;
      R.Bottom := R.Bottom - 4;
      Data^.FChildTree.BoundsRect := R;
    end;
  end;
end;

procedure TForm1.OnUpdateScrollBars(Sender: TBaseVirtualTree; DoRepaint: Boolean);
begin
  ResizeSubTrees(Sender);
end;

end.

Unit1.dfm

object Form1: TForm1
  Left = 0
  Top = 0
  Caption = 'Form1'
  ClientHeight = 282
  ClientWidth = 468
  Color = clBtnFace
  Font.Charset = DEFAULT_CHARSET
  Font.Color = clWindowText
  Font.Height = -11
  Font.Name = 'Tahoma'
  Font.Style = []
  OldCreateOrder = False
  OnCreate = FormCreate
  DesignSize = (
    468
    282)
  PixelsPerInch = 96
  TextHeight = 13
  object VirtualStringTree1: TVirtualStringTree
    Left = 8
    Top = 8
    Width = 371
    Height = 266
    Anchors = [akLeft,akTop,akRight,akBottom]
    Header.AutoSizeIndex = 0
    Header.Font.Charset = DEFAULT_CHARSET
    Header.Font.Color = clWindowText
    Header.Font.Height = -11
    Header.Font.Name = 'Tahoma'
    Header.Font.Style = []
    Header.Height = 21
    Header.Options = [hoColumnResize,hoDblClickResize,hoVisible]
    TabOrder = 0
    TreeOptions.MiscOptions = [toVariableNodeHeight]
    OnAfterAutoFitColumns = VirtualStringTree1AfterAutoFitColumns
    OnBeforeDrawTreeLine = VirtualStringTree1BeforeDrawTreeLine
    OnCollapsed = VirtualStringTree1Collapsed
    OnColumnResize = VirtualStringTree1ColumnResize
    OnExpanded = VirtualStringTree1Expanded
    OnFocusChanging = VirtualStringTree1FocusChanging
    OnFreeNode = VirtualStringTree1FreeNode
    OnMeasureItem = VirtualStringTree1MeasureItem
    ExplicitWidth = 581
    ExplicitHeight = 326
    Columns = <
      item
        Position = 0
        Width = 75
        WideText = 'Column 1'
      end
      item
        Position = 1
        Width = 75
        WideText = 'Column 2'
      end
      item
        Position = 2
        Width = 75
        WideText = 'Column 3'
      end>
  end
  object Button1: TButton
    Left = 385
    Top = 8
    Width = 75
    Height = 25
    Anchors = [akTop,akRight]
    Caption = 'Button1'
    TabOrder = 1
    OnClick = Button1Click
    ExplicitLeft = 595
  end
end

2.4.截图

（编辑：李大同）

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