Question

¿Como trabajar Multithreads en Delphi?

Answer 1

unit uMain; interface {$I CompVer.inc} uses {$IFDEF D6H} Variants, {$ENDIF} Windows, Messages, SysUtils, Classes, Graphics, Controls, Forms, Dialogs, StdCtrls, DB, ABSMain, Grids, DBGrids; type TMainForm = class(TForm) DBGrid1: TDBGrid; dsChat: TDataSource; dbDemos: TABSDatabase; tblChat: TABSTable; GroupBox2: TGroupBox; Label1: TLabel; Label2: TLabel; Button1: TButton; Button2: TButton; procedure FormCreate(Sender: TObject); procedure FormDestroy(Sender: TObject); procedure Button1Click(Sender: TObject); procedure Button2Click(Sender: TObject); private { Private declarations } public { Public declarations } end; TChatMemberThread = class(TThread) private FName: string; FSession: TABSSession; FDatabase: TABSDatabase; FTable: TABSTable; procedure RefreshTable; protected procedure Execute; override; public constructor Create(Name: string); destructor Destroy; override; end; const ChatMessages: array[0..9] of string = ('Hi', 'Hello', 'I''m here', 'Banzay!', 'Cool', 'how are you?', 'fine', 'who is here', 'I''m here', 'BzzzZzzz...'); const ChatMembersNames: array[0..9] of string = ('Roger', 'Janet', 'Dana', 'Bill', 'Kim', 'Bruce', 'Phil', 'Roberto', 'Michael', 'Claudia'); const DataBaseFileName: String = '..\..\Data\Demos.abs'; var MainForm: TMainForm; implementation {$IFDEF D6H} uses StrUtils; {$ELSE} function RandomFrom(const AValues: array of string): string; begin Result := AValues[Random(High(AValues) + 1)]; end; {$ENDIF} {$R *.dfm} { TChatMemberThread } constructor TChatMemberThread.Create(Name: string); begin inherited Create(True); FName := Name; FreeOnTerminate := True; FSession := TABSSession.Create(nil); FSession.AutoSessionName := True; FDatabase := TABSDatabase.Create(nil); FDatabase.DatabaseName := 'db_' + Name + '_' + IntToStr(Random(1000)); FDatabase.DatabaseFileName := ExtractFilePath(Application.ExeName) + DataBaseFileName; FDatabase.SessionName := FSession.SessionName; FDatabase.MultiUser := True; FDatabase.Open; FTable := TABSTable.Create(nil); FTable.SessionName := FSession.SessionName; FTable.DatabaseName := FDatabase.DatabaseName; FTable.TableName := 'Chat'; FTable.Open; end; destructor TChatMemberThread.Destroy; begin FTable.Free; FDatabase.Free; FSession.Free; inherited; end; procedure TChatMemberThread.Execute; var I: Integer; begin for I := 0 to 20 do begin if Terminated then Exit; if MainForm.tblChat.Active and MainForm.tblChat.Exists then begin FTable.AppendRecord([FName, RandomFrom(ChatMessages)]); { refreshing must be done in a synchronzied method since it will modify the contents of the grid and the grid can only be modified from the main VCL thread } Synchronize(RefreshTable); Sleep(Random(100)); end; end; end; procedure TMainForm.FormCreate(Sender: TObject); begin Randomize; dbDemos.DatabaseFileName := ExtractFilePath(Application.ExeName) + DataBaseFileName; tblChat.CreateTable; tblChat.Open; end; procedure TMainForm.FormDestroy(Sender: TObject); begin tblChat.DeleteTable; end; procedure TMainForm.Button1Click(Sender: TObject); var I: Integer; begin for I := 0 to 9 do with TChatMemberThread.Create(ChatMembersNames[I]) do begin Priority := tpLower; Resume; end; end; procedure TMainForm.Button2Click(Sender: TObject); begin tblChat.Close; tblChat.EmptyTable; tblChat.Open; end; procedure TChatMemberThread.RefreshTable; begin MainForm.tblChat.Refresh; end; end.