学习 TTreeView [15] - 连接数据库 (作为给 "丁永其" 和 "DELPHI万岁" 两位朋友的回复)

本例效果图:

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unit Unit1;



interface



uses

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

  Dialogs, Grids, DBGrids, DB, DBClient, StdCtrls, ComCtrls, ExtCtrls;



type

  TForm1 = class(TForm)

    DataSource1: TDataSource;

    ClientDataSet1: TClientDataSet;

    DBGrid1: TDBGrid;

    TreeView1: TTreeView;

    Splitter1: TSplitter;

    procedure FormCreate(Sender: TObject);

    procedure TreeView1Change(Sender: TObject; Node: TTreeNode);

  end;



var

  Form1: TForm1;



implementation



{$R *.dfm}



procedure TForm1.FormCreate(Sender: TObject);

var

  i: Integer;

  node: TTreeNode;

  List: TStringList;

  s: string;

begin

  {country.xml 是 Delphi 的数据示范文件, 也可以用 country.cds}

  ClientDataSet1.FileName := 'c:\temp\country.xml';

  ClientDataSet1.Active := True;

  DataSource1.DataSet := ClientDataSet1;

  DBGrid1.DataSource := DataSource1;

  {上面四行是让数据构件互相挂接, 也可以在设计时设定}



  {建立 List}

  List := TStringList.Create;

  List.Sorted := True;           {指定排序}

  List.Duplicates := dupIgnore;  {避免重复}



  {把数据加入到 TreeView}

  for i := 0 to ClientDataSet1.FieldDefs.Count - 1 do

  begin

    node := TreeView1.Items.Add(nil, ClientDataSet1.FieldDefs[i].Name); {字段名}



    {为避免数据重复, 先把数据给 List}

    List.Clear;

    ClientDataSet1.First;

    while not ClientDataSet1.Eof do

    begin

      List.Add(ClientDataSet1.Fields[i].value);

      ClientDataSet1.Next;

    end;

    {把 List 中的数据加入到 TreeView}

    for s in List do TreeView1.Items.AddChild(node, s);

  end;



  List.Free;

end;



procedure TForm1.TreeView1Change(Sender: TObject; Node: TTreeNode);

begin

  if Node.Parent <> nil then

  begin

    {下面的 Filter 其实就是 SQL 查询语句, 如果用其他数据库替换就是}

    ClientDataSet1.Filter := Node.Parent.Text + '=''' + Node.Text + '''';

    ClientDataSet1.Filtered := True;

  end else ClientDataSet1.Filtered := False; {选字段名时取消过虑}

end;



end.


 
   

附数据库样本: <?xml version="1.0" standalone="yes"?> <DATAPACKET Version="2.0"> <METADATA> <FIELDS> <FIELD attrname="Name" fieldtype="string" WIDTH="24"/> <FIELD attrname="Capital" fieldtype="string" WIDTH="24"/> <FIELD attrname="Continent" fieldtype="string" WIDTH="24"/> <FIELD attrname="Area" fieldtype="r8"/> <FIELD attrname="Population" fieldtype="r8"/> </FIELDS> <PARAMS DEFAULT_ORDER="1" PRIMARY_KEY="1" LCID="2057"/> </METADATA> <ROWDATA> <ROW Name="Argentina" Capital="Buenos Aires" Continent="South America" Area="2777815" Population="32300003"/> <ROW Name="Bolivia" Capital="La Paz" Continent="South America" Area="1098575" Population="7300000"/> <ROW Name="Brazil" Capital="Brasilia" Continent="South America" Area="8511196" Population="150400000"/> <ROW Name="Canada" Capital="Ottawa" Continent="North America" Area="9976147" Population="26500000"/> <ROW Name="Chile" Capital="Santiago" Continent="South America" Area="756943" Population="13200000"/> <ROW Name="Colombia" Capital="Bagota" Continent="South America" Area="1138907" Population="33000000"/> <ROW Name="Cuba" Capital="Havana" Continent="North America" Area="114524" Population="10600000"/> <ROW Name="Ecuador" Capital="Quito" Continent="South America" Area="455502" Population="10600000"/> <ROW Name="El Salvador" Capital="San Salvador" Continent="North America" Area="20865" Population="5300000"/> <ROW Name="Guyana" Capital="Georgetown" Continent="South America" Area="214969" Population="800000"/> <ROW Name="Jamaica" Capital="Kingston" Continent="North America" Area="11424" Population="2500000"/> <ROW Name="Mexico" Capital="Mexico City" Continent="North America" Area="1967180" Population="88600000"/> <ROW Name="Nicaragua" Capital="Managua" Continent="North America" Area="139000" Population="3900000"/> <ROW Name="Paraguay" Capital="Asuncion" Continent="South America" Area="406576" Population="4660000"/> <ROW Name="Peru" Capital="Lima" Continent="South America" Area="1285215" Population="21600000"/> <ROW Name="United States of America" Capital="Washington" Continent="North America" Area="9363130" Population="249200000"/> <ROW Name="Uruguay" Capital="Montevideo" Continent="South America" Area="176140" Population="3002000"/> <ROW Name="Venezuela" Capital="Caracas" Continent="South America" Area="912047" Population="19700000"/> </ROWDATA> </DATAPACKET>

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