delphi 简单的倒计时算法

unit PPTTimeFrm;

interface

uses

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

  Dialogs,  ExtCtrls, StdCtrls, DateUtils;

type

  TFrmPPTTime = class(TForm)

    Timer1: TTimer;

    lblTitle: TLabel;

    procedure Timer1Timer(Sender: TObject);

    procedure FormCloseQuery(Sender: TObject; var CanClose: Boolean);

    procedure FormShow(Sender: TObject);

    procedure FormCreate(Sender: TObject);

    procedure FormDblClick(Sender: TObject);

  private

    { Private declarations }

    TimerCount: Integer;

    StartTime: TDateTime;

    procedure ResetTimer;

  public

    { Public declarations }

  end;

var

  FrmPPTTime: TFrmPPTTime;

implementation

{$R *.dfm}

procedure TFrmPPTTime.FormCloseQuery(Sender: TObject; var CanClose: Boolean);

begin

  CanClose := MessageDlg('您确认需要退出吗？',

    mtConfirmation, [mbYes, mbNo], 0) = mrYes;

  if CanClose then

    Timer1.Enabled := False;

end;

procedure TFrmPPTTime.FormCreate(Sender: TObject);

begin

  StartTime := Time();

  Self.ClientHeight := 19;

  Self.Width := 120;

end;

procedure TFrmPPTTime.FormDblClick(Sender: TObject);

begin

  ResetTimer;

end;

procedure TFrmPPTTime.FormShow(Sender: TObject);

begin

  ResetTimer;

  Timer1.Enabled := True;

end;

procedure TFrmPPTTime.ResetTimer;

var

  num: Integer;

begin

  num := StrToIntDef(InputBox('倒计时器', '请输入您要计时的分钟数：', '5'), 0);

  if num > 0 then

    begin

      TimerCount := num;

      StartTime := Time();

    end

  else

    TimerCount := 0;

end;

procedure TFrmPPTTime.Timer1Timer(Sender: TObject);

var

  num1, num2: Double;

begin

  if Timer1.Tag = 0 then

  begin

    Self.Top := 4;

    Self.Left := Screen.Width - Self.Width - 2;

    Timer1.Tag := 1;

  end;

  Caption := 'Time: ' + FormatDatetime('HH:MM:SS', Time());

  if TimerCount > 0 then

  begin

    num2 := MinutesBetween(Time(), StartTime);

    num1 := TimerCount - num2;

    if num1 > 0 then

      lblTitle.Caption := Format('已过 %g 分钟', [num2])

    else

      TimerCount := 0;

  end;

  if TimerCount = 0 then

    lblTitle.Caption := Format('计时器停止！',

      [TimerCount - SecondsBetween(Time(), StartTime)]);

end;

end.