浅谈Delphi高效使用TreeView

Posted 2022-08-09 jijm123

本来我一直都是使用递归算法, 效率很低

下边这段代码是我原来写的

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procedure TForm1.GetDepartmentMsg;
var
  Test, Test2 : TTreeNode;
  procedure NodeAdd(Test : TTreeNode; DepartmentId : string);
  var
    Testlevel : TTreeNode;
    TestQuery : TADOQuery;
  begin
    try
      TestQuery := TADOQuery.Create(Nil);
      TestQuery.Connection := ADOConnection1;
      With TestQuery do
      begin
        Close;
        SQL.Text := ‘Select  DepartmentID  ,NAME from  Department where DepartmentID like ‘‘‘+DepartmentId+‘%‘‘ and Len(DepartmentId) = ‘ + IntToStr(Length (DepartmentId) + 2) +  ‘Group by DepartmentID ,name order by DepartmentID ‘  ;
        Open;
        if Not IsEmpty then
        begin
          while not Eof do
          begin
            Testlevel := TreeView1.Items.AddChild(Test,TestQuery.fieldbyName(‘Name‘).AsString + ‘ | ‘+ TestQuery.fieldbyName(‘DepartmentId‘).AsString);
            NodeAdd(Testlevel,TestQuery.fieldbyName(‘DepartmentId‘).AsString);
            Testlevel.ImageIndex := Testlevel.Level -1;
            Testlevel.SelectedIndex := Testlevel.Level -1;
            Next;
          end;
        end;
      end;
    finally
      TestQuery.free;
    end;
end;

begin
  Test := TreeView1.Items.Add(nil,‘ ***** | 00‘);
  Test.ImageIndex := 1;
  with Query1 do
  begin
    Close;
    Sql.Text := ‘Select * from Department where State = ‘‘正常‘‘ and DepartmentLevel = ‘‘1‘‘ ‘;
    Open;
  end;
  Query1.First;
  TreeView1.Items.BeginUpdate;
  while not Query1.Eof do
  begin
    Test2 := TreeView1.Items.AddChild(Test,Query1.fieldbyName(‘Name‘).AsString + ‘ | ‘+ Query1.fieldbyName(‘DepartmentId‘).AsString) ;
    NodeAdd(Test2,Query1.fieldbyName(‘DepartmentId‘).AsString);
    Query1.Next;
  end;

  TreeView1.Items.EndUpdate;
  Query1.Close;
end;

今天无事测试了这段代码 时间是6-7秒左右

下边这段改进后的,不使用递归

 

procedure TForm1.NewGetDepartmentMsg;
const
  DivNum = 2;
var
  nLevel: Integer;
  pNodes: array[0..1023] of TTreeNode;
  DepartmentID, Name: string;
  Str: string;
begin
  Str := ‘Select DepartmentID, Name from Department  order by DepartmentID‘;
  with adoquery1 do
  begin
    Close;
    Sql.clear;
    Sql.add(Str);
    Open;
  end;

  TreeView1.Items.Clear;
  TreeView1.Items.BeginUpdate;
  pNodes[0] := TreeView1.Items.Add(nil, ‘***‘);
  if Not ADOQuery1.IsEmpty then
    while not ADOQuery1.Eof do
    begin
      DepartmentID := ADOQuery1.fieldbyName(‘DepartmentID‘).AsString;
      Name := ADOQuery1.fieldbyName(‘Name‘).AsString;
      nLevel := Length(DepartmentID) div DivNum ;
      pNodes[nLevel] := TreeView1.Items.AddChild(pNodes[nLevel - 1], DepartmentID + ‘ | ‘ + Name);
      ADOQuery1.Next;
    end;
  TreeView1.Items.EndUpdate;
  ADOQuery1.Close;
end;

这个算法主要合理利用了 ‘Select DepartmentID, Name from Department  order by DepartmentID‘ 来排序, 这就保证了 

pNodes[nLevel] := TreeView1.Items.AddChild(pNodes[nLevel - 1], DepartmentID + ‘ | ‘ + Name);

他的上级结点不为空

这段代码我一测试, 大概是0.2秒左右, 数据和上边那段代码处理一样的数据

这样写肯定是有缺陷的, 也不是什么情况下都能使用

写得不对的地方,欢迎批评和指正,谢谢