datatree和數據庫綁定的最少代碼

2019-11-18 17:57:30

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unit mmslibrarypage;

interface

uses
Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
Dialogs, ImgList, VirtualTrees, ComCtrls, ToolWin, mpToolBar,basicModal,DataModal,
database,myScroll,insertdemon,MySQL,newmmsForlibrary;

type
TMMSLibraryForm = class(TPageForm)
    mainToolBar: TmpToolBar;
    btnNewMMS: TToolButton;
    btnDelete: TToolButton;
    DataTree: TVirtualStringTree;
    ilImages: TImageList;
    btnImport: TToolButton;
    btn2: TToolButton;
    btn3: TToolButton;
    btn4: TToolButton;
    btn5: TToolButton;
    btnExport: TToolButton;
    btnRefresh: TToolButton;
    PRocedure FormCreate(Sender: TObject);
    procedure btnNewMMSClick(Sender: TObject);
    procedure btnDeleteClick(Sender: TObject);
    procedure btnImportClick(Sender: TObject);
    procedure btnExportClick(Sender: TObject);
    procedure FormShow(Sender: TObject);
    procedure btnRefreshClick(Sender: TObject);
    procedure FormDestroy(Sender: TObject);
    procedure DataTreeGetText(Sender: TBaseVirtualTree; Node: PVirtualNode;
      Column: TColumnIndex; TextType: TVSTTextType;
      var CellText: WideString);
    procedure DataTreeInitNode(Sender: TBaseVirtualTree; ParentNode,
      Node: PVirtualNode; var InitialStates: TVirtualNodeInitStates);

private
    { Private declarations }
    stringlist:TStringList;
public
    procedure refreshtree();
end;

procedure GetMMSFromLibrary(dparam: TStringList; mysql_rows: PMYSQL_ROW);

type
PMMSTreeNode=^TMMStreeNode;

//自定義的datatree的結構
TMMStreeNode=record
   mmsid:string;
   mmstype:string;
   mmssmil:string;
   mmssize:Integer;
   mmssubject:string;
end;

var
MMSLibraryForm: TMMSLibraryForm;

implementation

{$R *.dfm}

procedure TMMSLibraryForm.FormCreate(Sender: TObject);
begin
Self.Font:=application.MainForm.Font;                                       //保持程序中字體一致
stringlist:=TStringList.Create;                                                       //保存要顯示的數據
DataTree.NodeDataSize:=SizeOf(TMMStreeNode);                 //初始化datatree的節點大小
end;

procedure TMMSLibraryForm.FormShow(Sender: TObject);
var
pdbinfo: PDatabaseInfo;
column : TVirtualTreeColumn;
Header : TStrings;
i      : Integer;
node   : PVirtualNode;
data   : PINT;

sql : string;
pnode1 : PMMSTreeNode;
begin
Header:=TStringList.Create;

//添加顯示的列名
if trim(Header.Text)='' then
begin
    Header.Add('ID');
    Header.Add('Type');
    Header.Add('Smil 1.0/2.0');
    Header.Add('Size(B)');
    Header.Add('Subject');
end;

//設置列的顯示

for i:=0 to Header.Count-1 do
begin
    column:= DataTree.Header.Columns.Add;
    column.Text:= Header[I];
    column.Width:=dataTree.ClientWidth div 6;
    if i=4 then
       column.Width:= dataTree.ClientWidth div 3-10;
end;

// 連接數據庫，獲取指定的數據庫（是不是忒簡單）

pdbinfo:=currentdatabase.databases.GetByIndex(0);

Refreshtree;

end;

procedure TMMSLibraryForm.refreshtree();
var
sql : string;
begin
DataTree.Clear;
stringlist.Clear;

sql:='select MMS_ID,MMS_Type,MMS_Smil,MMS_Size,MMS_Subject from mmslibrary';

//回調函數：讓被調用者調用調用者自身的函數。執行ExeuteSQlQurey時調用了GetMMSFromLibrary

(***********************************************************************************************************

procedure TDatabase.ExeuteSQlQurey(dparam: Pointer; sql: string; callback: TDbDataCallBack);
var
aHandle, db: pmysql;
qresult: PMYSQL_RES;
mysql_rows: PMYSQL_ROW;
iRtn, fcount, i: Integer;
begin

try
    aHandle := mysql_init(nil);
   //mysql_real_connect(aHandle, nil, nil, nil, nil, 0, nil, 0);
    if commonconfig.remotemode = 0 then
      db := mysql_real_connect(aHandle, nil, nil, nil, PAnsichar(FCurrentDataBase), 0, nil, 0)
    else
      db := mysql_real_connect(aHandle, PAnsichar(RHost), PAnsichar(RUser), PAnsichar(RPassWord), PAnsichar(FCurrentDataBase), 0, nil, 0);

    if db <> nil then
    begin
      iRtn := mysql.mysql_query(db, Pchar(sql));
      if iRtn = 0 then
      begin
        qresult := mysql.mysql_store_result(db);
        if qresult <> nil then
        begin
          fcount := mysql.mysql_num_rows(qresult);
          for i := 0 to fcount - 1 do
          begin
            mysql_rows := mysql.mysql_fetch_row(qresult);
            callback(dparam, mysql_rows);
          end;
        end;
        mysql.mysql_free_result(qresult);
      end;
    end;
finally
    mysql_Close(db);
end;

end;

*************************************************************************************************************)

currentdatabase.ExeuteSQlQurey(stringlist,sql,@GetMMSFromLibrary);

DataTree.RootNodeCount:=stringlist.Count div 5 ; //小技巧啦
DataTree.Refresh;
end;

//daparam即是currentdatabase.ExeuteSQlQurey(stringlist,sql,@GetMMSFromLibrary);中的stringlist，

//即用被調用者的值（mysql_rows ）初始化調用者的參數

//這個觀點很重要，使用也很廣泛和特殊
procedure GetMMSFromLibrary(dparam: TStringList; mysql_rows: PMYSQL_ROW);
begin
    dparam.Add(mysql_rows[0]);
    dparam.Add(mysql_rows[1]);
    dparam.Add(mysql_rows[2]);
    dparam.Add(mysql_rows[3]);
    dparam.Add(mysql_rows[4]);
end;

procedure TMMSLibraryForm.btnNewMMSClick(Sender: TObject);
begin
NewMMS:=TNewMMS.Create(MMSLibraryForm);
if NewMMS.ShowModal= mrok then
refreshtree;
end;

procedure TMMSLibraryForm.btnDeleteClick(Sender: TObject);
var
node:PVirtualNode;

sql:string;
begin
if DataTree.FocusedNode=nil then Exit;

node:=DataTree.FocusedNode;

sql:='delete from mmslibrary where MMS_ID="'+ stringlist[node.index * 5]+'"';
currentdatabase.ExecuteSqlNoQurey(sql);
RefreshTree;

end;
procedure TMMSLibraryForm.btnImportClick(Sender: TObject);
var
dl:TOpenDialog;
begin
dl.Filter:='eml files|*.eml';

end;

procedure TMMSLibraryForm.btnExportClick(Sender: TObject);
begin
//
end;

procedure TMMSLibraryForm.btnRefreshClick(Sender: TObject);
begin
RefreshTree;
end;

procedure TMMSLibraryForm.FormDestroy(Sender: TObject);
begin
stringlist.Free;
inherited;
end;

procedure TMMSLibraryForm.DataTreeGetText(Sender: TBaseVirtualTree;
Node: PVirtualNode; Column: TColumnIndex; TextType: TVSTTextType;
var CellText: WideString);
var
i:Integer;
begin

//這是關鍵的步驟：將stringlist和datatree綁定。這個函數的解釋如下：

(**********************************************************************************************************

property OnGetText: TVSTGetTextEvent;

Description

This is one of the fundamental string tree events which must always be handled. The string tree will fire this event every time when it needs to know about the text of a specific node and column. This is mainly the case when the node appears in the visible area of the tree view (in other words it is not scrolled out of view) but also on some other occasions, including streaming, drag and drop and calculating the width of the node.

The node text is distinguished between two text types:

Normal text: If TextType is ttNormal return the main node caption for the specified column.
Static text: All text that you return when TextType is ttStatic will be displayed right beside the normal text (or left to it if the column's BidiMode is not bdLeftToRight, i.e. the column has right-to-left layout). Static text is used only for informational purposes; it cannot be selected or dragged and if the column is not wide enough to show all text it will not be shortened with an ellipsis (...) as normal text. The string tree will only query for static text if the StringOptions (see TreeOptions) include toShowStaticText. This is off by default.

When this event is fired the text parameter will always be initialized with the value of property DefaultText. To handle the event get your node data and then extract the string for the appropriate column and TextType.

Notes

Be sure that your event handler only contains absolutely necessary code. This event will be fired very often - easily a

few hundred times for medium sized trees with some columns defined when the tree is repainted completely.

For example it is far too slow to use Locate() on some Dataset, a database query result or table, and then get the text

from some TField. This may only work with in-memory tables or a client dataset. When you initialize your node data do

some caching and use these cached values to display the data.

************************************************************************************************************)

    for i:=0 to stringlist.Count div 5 -1 do
    begin
      case Column of
        0:CellText:=stringlist[node.index * 5];
        1:CellText:=stringlist[node.index * 5+1];
        2:CellText:=stringlist[node.index * 5+2];
        3:CellText:=stringlist[node.index * 5+3];
        4:CellText:=stringlist[node.index * 5+4];
      end;
    end;

end;

//這個函數居然可以不用也可以連數據庫，奇怪？

procedure TMMSLibraryForm.DataTreeInitNode(Sender: TBaseVirtualTree;
ParentNode, Node: PVirtualNode;
var InitialStates: TVirtualNodeInitStates);
var
Data: ^Int64;
begin
// Data := Sender.GetNodeData(Node);
// Data^ := Node.Index;
end;

end.

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