是否有可能使用VirtualStringTree作为主细节网格视图？

2018-06-12 05:46:39

好的，我在这里遇到了一些非常棘手的问题......我想将小标题绘制/使用到小孩节点。我认为这个想法是合理的，因为在子节点中包含标题看起来会很神奇，所以可以在表中指定子节点。 VST有或根本无法做到这一点？

谢谢你的帮助。

1.有没有办法将VirtualTreeView用于主/细网格视图？

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

2.如何为子节点细节网格视图创建功能齐全的标头？

考虑几种方法，如何模拟子节点的标题外观和行为我发现对于使用嵌套树视图来实现详细的网格视图非常有用。这将为您带来细节数据的分离性，并允许您将整个模拟最小化，以将嵌套树视图定位到子节点的矩形中。

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，比如在子节点内的控件的定位可以是多么复杂（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。 已知问题和限制：

这个项目经过编写和测试，每个根节点只能使用一个孩子，所以当你超过这个限制时，不要对此行为感到惊讶，因为这是没有设计的，甚至没有经过测试

当主树的双击列大小调整列的大小时，嵌套树视图会在画布由ScrollDC函数滚动时用线条透支

保持VirtualTree代码不变我重写了滚动条更新的方法。当滚动条需要更新时，它用于更新嵌套树视图边界

当前的OnExpanded实现会在范围和滚动位置固定之前触发事件，这会导致代码更复杂并带来很大的弱点 - 在显示树之后更新详细树视图的界限，有时可以看到

2.3。 项目代码

它是在Delphi 2009中针对Delphi 7中的应用编写和测试的。关于下一个代码的评论版本，请follow this link ：

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, NewNode: PVirtualNode; OldColumn, 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, hoDrag, hoShowSortGlyphs, 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

在这里输入图像描述

链接地址: http://www.djcxy.com/p/35027.html

上一篇: Is it possible to use VirtualStringTree for a master detail grid view?

下一篇: Embedding Controls In Cells