Delphi中根據分類數據生成樹形結構的最優方法(2)

4． 程序源代碼：

unit Unit1;
interface
uses
Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms, Dialogs, DB, DBTables, ImgList, ComCtrls , PubVar, Grids, DBGrids, Menus , StrUtils, StdCtrls;
type
TForm1 = class(TForm)
Tree: TTreeVIEw;
ImageList1: TImageList;
Table1: TTable;
DataSource1: TDataSource;
DBGrid1: TDBGrid;
PopupMenu1: TPopupMenu;
AddMenu: TMenuItem;
DeleteMenu: TMenuItem;
RenameMenu: TMenuItem;
Query1: TQuery;
DataSource2: TDataSource;
procedure AddMenuClick(Sender: TObject);//點擊增加子項菜單
procedure RenameMenuClick(Sender: TObject);//點擊重命名菜單
procedure DeleteMenuClick(Sender: TObject); //點擊刪除該項菜單
procedure FormCreate(Sender: TObject);
procedure TreeClick(Sender: TObject);
private
{ Private declarations }
public
{ Public declarations }
procedure LoadTree(treeDB:TDBDataSet);//初始化樹
procedure UpdateTree(curNode:TTreenode; nodeTxt:string; state:string);//更新樹
function GetNodeLevel(sFormat,sCode:string):integer;//獲得節點層數
function GetCurrChildNodeMaxMa(curNode:TTreenode):string;
//獲得當前節點子節點的最大編碼
function GetCurrentNodeBianma(curNode:TTreenode):string;//獲得當前節點的編碼
procedure UpdateTable(bianma:string; cityname:string ;state:string); //更新數據庫
end;
var
Form1: TForm1;
CurrentTreeNode: TTreeNode;
// AddChildeTreeNode: TTreeNode;
// flag:boolean; //用於標識是否需要在重命名樹結點時更新數據
implementation
uses AddChildUnit,RenameItemUnit;
{$R *.dfm}
procedure TForm1.LoadTree(treeDB:TDBDataSet);//初始化樹
var
curID,nodeTxt:string;
level:integer;
mynode:array[0..3] of TTreenode;
begin //初始化變量
Screen.Cursor:=crHourGlass;
tree.Enabled:=True;
tree.Items.Clear;
level:=0 ;
//設置根節點
mynode[level]:=tree.items.add(Tree.Topitem,cTreeRootTxt);
mynode[level].ImageIndex:=1;
//遍歷數據表，利用編碼字段記錄排序規律，依次添加樹節點
with treeDB do
begin
try
if not Active then open;
first;
while not Eof do
begin
curID:=trim(FIEldByName(’bianma’).AsString);
nodeTxt:=curID+’-’+trim(FIEldByName(’cityname’).AsString);
level:=GetNodeLevel(cTreeCodeFormat,curID);
//這裡返回代碼的層次數
if level〉0 then
begin
//增加下一節點時，用添加子節點的方法可輕松實現節點間的層次關系
//注意：這裡的父節點是用當前節點的上一級節點mynode[level-1]
mynode[level]:= tree.items.addchild(mynode[level-1],nodeTxt);
mynode[level].ImageIndex:=2;
end;
next;//下一條記錄
end;
finally
close;
End;
mynode[0].expand(False);
Screen.Cursor:=crDefault;
end;
end;
function TForm1.GetNodeLevel(sFormat,sCode:string):integer;//獲得節點層數
var i,level,iLen:integer;
begin
level:=-1 ;
iLen:=0;
if (sFormat〈〉’’) and (sCode〈〉’’) then
for i:=1 to Length(sFormat) do //分析編碼格式，找出當前代碼層次
begin
iLen:=iLen+StrToInt(sFormat[i]);
if Length(sCode)=iLen then
begin level:=i; break; end;
end;
result:=level;
end;
//以下過程在新增、刪除、修改記錄時，同步更新樹形結構
procedure TForm1.UpdateTree(curNode:TTreenode; nodeTxt:string; state:string);
Begin
if UpperCase(state)=’ADD’ then
begin
curNode:=tree.items.addchild(curNode,nodeTxt);
curNode.ImageIndex:=2;
end;
if UpperCase(state)=’DEL’ then
begin
curNode.DeleteChildren;
curNode.delete;
end;
if UpperCase(state)=’EDI’ then curNode.Text:=nodeTxt;
end;
procedure TForm1.AddMenuClick(Sender: TObject);//點擊增加子項菜單
var AddChildText, AddTableText,maxbianma : string;
begin
AddChildForm.Label1.Caption:=’為“’+CurrentTreeNode.Text+’“增加子項 ’;
if AddChildForm.ShowModal=mrOk then
begin
AddChildText:=AddChildForm.Edit1.Text;
maxbianma:=GetCurrChildNodeMaxMa(CurrentTreeNode);
if (CurrentTreeNode.Text=’城市’) and (maxbianma=’1000’) then
maxbianma:=’11’//如果當前節點為根節點，且只有一個子節點，使增加節點編碼為11
else if CurrentTreeNode.Text=’城市’ then
maxbianma:=IntToStr(StrToInt(LeftStr(maxbianma,2))+1)
else
maxbianma:=IntToStr(StrToInt(maxbianma)+1); //使子項編碼自動增1
if maxbianma〈〉’0’ then
begin
//增加樹子層
AddTableText:=maxbianma+’-’+AddChildText;
UpdateTree(CurrentTreeNode,AddTableText,’add’); //更新樹
UpdateTable(maxbianma,AddChildText,’add’); //更新表
ShowMessage(’添加成功!’);
end
else ShowMessage(’此層為最低子層，不能在該層增加子層’);
AddChildForm.Edit1.Text:=’’;
end;
end;
function TForm1.GetCurrChildNodeMaxMa(curNode:TTreenode):string;
//獲得當前節點子節點的最大編碼
var
aSQL,maxbianma:string;
li_pos:integer;
begin
li_pos:=pos(’-’,curNode.Text);
if li_pos=7 then
begin result:=’-1’; exit; end;
if (li_pos=0) and (not(curNode.HasChildren)) then // 如果當前節點為根節點並且沒有子節點
begin
result:=’9’; //使根節點第一個節點編碼為10
exit;
end
else begin
aSQL:=’select bianma from city_tree where bianma like “’ + MidStr(curNode.Text, 1, li_pos-1) + ’%“’;
Query1.UnPrepare;
Query1.Close;
Query1.SQL.Clear;
Query1.SQL.Text:=aSQL;
Query1.Prepare;
Query1.ExecSQL;
Query1.Active:=true;
Query1.Last;
maxbianma:=Query1.fIEldbyname(’bianma’).AsString;
if Query1.RecordCount=1 then//如果當前項沒有子項
maxbianma:=maxbianma+’00’;
Query1.Active:=false;
end;
result:=maxbianma;
end;
procedure TForm1.RenameMenuClick(Sender: TObject);//點擊重命名菜單
var
bianma:string;
itemtext:string; //用於重命名時保存輸入的Edit.text
begin
RenameItemForm.Label1.Caption:=’將“’+CurrentTreeNode.Text+’“命名為 ’;
if RenameItemForm.ShowModal=mrOk then
begin
itemtext:=RenameItemForm.Edit1.Text;
bianma:=GetCurrentNodeBianma(CurrentTreeNode);
Table1.Locate(’bianma’,bianma,[]);
UpdateTable(’’,itemtext,’edi’);
itemtext:=bianma+’-’+itemtext;
UpdateTree(CurrentTreeNode,itemtext,’edi’);
ShowMessage(’重命名成功!’);
end;
end;
//以下過程在新增、刪除、修改記錄時，同步更新數據庫表
procedure TForm1.UpdateTable(bianma:string; cityname:string ;state:string); //更新數據庫
begin
if state=’add’ then
begin
Table1.Active:=True;
Table1.Insert;
Table1.SetFIElds([bianma,cityname]);
Table1.Post;
end;
if state=’del’ then
begin
Table1.Active:=True;
Table1.Locate(’bianma’,bianma,[]);
Table1.Delete;
end;
if state=’edi’ then
begin
Table1.Edit;
Table1.FIEldByName(’cityname’).AsString:=cityname;
Table1.Post;
end;
end;
procedure TForm1.DeleteMenuClick(Sender: TObject); //點擊刪除該項菜單
var
bianma:string;
begin
CurrentTreeNode.expand(False);
if CurrentTreeNode.Text=’城市’ then //如果當前節點為根節點
begin
ShowMessage(’不能刪除根節點’);
exit;//退出該過程
end;
if CurrentTreeNode.HasChildren then //如果當前節點具有子項
begin
ShowMessage(’請先刪除其子項’);
exit;//退出該過程
end;
if Application.MessageBox(PChar(’真的要刪除“’+CurrentTreeNode.Text+’“這項嗎?’),’警告’,MB_YESNO)=mrYES then
begin
bianma:=GetCurrentNodeBianma(CurrentTreeNode);
UpdateTree(CurrentTreeNode,’’,’del’);
UpdateTable(bianma,’’,’del’);
ShowMessage(’刪除成功!’);
Table1.Refresh;//更新TBGrid控件中的顯示
Table1.Active:=true;
CurrentTreeNode:=Form1.tree.selected;
end;
end;
function TForm1.GetCurrentNodeBianma(curNode:TTreeNode):string;//獲得當前節點的編碼
var
li_pos:integer;
bianma:string;
begin
li_pos:=pos(’-’,curNode.Text);
bianma:=MidStr(curNode.Text,1,li_pos-1);
result:=bianma;
end;
procedure TForm1.FormCreate(Sender: TObject);
begin
LoadTree(Table1);
Table1.Active:=true;
end;
procedure TForm1.TreeClick(Sender: TObject);
begin
CurrentTreeNode:=Form1.tree.selected; //獲得當前節點
end;
end.
unit PubVar;
interface
uses
SysUtils, WinTypes, WinProcs, Messages, Classes, Graphics, Controls, Forms, DbTables, StdCtrls, ExtCtrls, Buttons, Dialogs,Registry,Db, ComCtrls;
const
cTreeCodeFormat=’222’; //編碼格式:xx xx xx
cTreeMaxLevel=3; //最大編碼(樹節點)層次
cTreeRootTxt=’城市’; //樹的根節點名稱
implementation
end.

5． 編譯運行結果圖：(附後)

四、 小結：

本程序與編碼法快速生成樹形結構，通過TreeView控件直接操作數據表，實現了對表的數據導航。如果你想通過點擊TreeVIEw控件某項直接顯示該項的相關信息，可在該程序的基礎上進行修改。

原文載於《電腦編程技巧與維護》2003年第一期P27