mainfrm.pas

《Delphi开发人员指南》配书原码

unit MainFrm;

interface

uses
  Windows, Messages, SysUtils, Classes, Graphics, Controls,
  Forms, Dialogs, StdCtrls, Mask, Persrec, ComCtrls;

const
  // Declare the file name as a constant
  FName = 'PERSONS.DAT';

type

  TMainForm = class(TForm)
    edtFirstName: TEdit;
    edtLastName: TEdit;
    edtMI: TEdit;
    meAge: TMaskEdit;
    lblFirstName: TLabel;
    lblLastName: TLabel;
    lblMI: TLabel;
    lblBirthDate: TLabel;
    lblAge: TLabel;
    btnFirst: TButton;
    btnNext: TButton;
    btnPrev: TButton;
    btnLast: TButton;
    btnAppend: TButton;
    btnUpdate: TButton;
    btnClear: TButton;
    lblRecNoCap: TLabel;
    lblRecNo: TLabel;
    lblNumRecsCap: TLabel;
    lblNoRecs: TLabel;
    dtpBirthDay: TDateTimePicker;
    procedure FormCreate(Sender: TObject);
    procedure FormDestroy(Sender: TObject);
    procedure FormShow(Sender: TObject);
    procedure btnAppendClick(Sender: TObject);
    procedure btnUpdateClick(Sender: TObject);
    procedure btnFirstClick(Sender: TObject);
    procedure btnNextClick(Sender: TObject);
    procedure btnLastClick(Sender: TObject);
    procedure btnPrevClick(Sender: TObject);
    procedure btnClearClick(Sender: TObject);
  public
    PersonRec: TPersonRec;
    RecordStream: TRecordStream;
    procedure ShowCurrentRecord;
  end;

var
  MainForm: TMainForm;

implementation

{$R *.DFM}

procedure TMainForm.FormCreate(Sender: TObject);
begin
  { If the file does not exist, then create it, otherwise, open it for
    both read and write access. This is done by instantiating
    a TRecordStream }
  if  FileExists(FName) then
    RecordStream := TRecordStream.Create(FName, fmOpenReadWrite)
  else
    RecordStream := TRecordStream.Create(FName, fmCreate);
end;

procedure TMainForm.FormDestroy(Sender: TObject);
begin
  RecordStream.Free; // Free the TRecordStream instance
end;

procedure TMainForm.ShowCurrentRecord;
begin
  // Read the current record.
  RecordStream.ReadRec(PersonRec);
  // Copy the data from the PersonRec to the form's controls
  with PersonRec do
  begin
    edtFirstName.Text := FirstName;
    edtLastName.Text  := LastName;
    edtMI.Text        := MI;
    dtpBirthDay.Date  := BirthDay;
    meAge.Text        := IntToStr(Age);
  end;
  // Show the record number and total records on the main form.
  lblRecNo.Caption  := IntToStr(RecordStream.CurRec);
  lblNoRecs.Caption := IntToStr(RecordStream.NumRecs);
end;

procedure TMainForm.FormShow(Sender: TObject);
begin
  // Display the current record only if one exists.
  if RecordStream.NumRecs <> 0 then
     ShowCurrentRecord;
end;


procedure TMainForm.btnAppendClick(Sender: TObject);
begin
  // Copy the contents of the form controls to the PersonRec record
  with PersonRec do
  begin
    FirstName := edtFirstName.Text;
    LastName  := edtLastName.Text;
    MI        := edtMI.Text;
    BirthDay  := dtpBirthDay.Date;
    Age       := StrToInt(meAge.Text);
  end;
  // Write the new record to the stream
  RecordStream.AppendRec(PersonRec);
  // Display the current record.
  ShowCurrentRecord;
end;

procedure TMainForm.btnUpdateClick(Sender: TObject);
begin
  { Copy the contents of the form controls to the PersonRec and write
    it to the stream }
  with PersonRec do
  begin
    FirstName := edtFirstName.Text;
    LastName  := edtLastName.Text;
    MI        := edtMI.Text;
    BirthDay  := dtpBirthDay.Date;
    Age       := StrToInt(meAge.Text);
  end;
  RecordStream.WriteRec(PersonRec);
end;

procedure TMainForm.btnFirstClick(Sender: TObject);
begin
  { Go to the first record in the stream and display it as long as
    there are records that exist in the stream }
  if RecordStream.NumRecs <> 0 then
  begin
    RecordStream.First;
    ShowCurrentRecord;
  end;
end;

procedure TMainForm.btnNextClick(Sender: TObject);
begin
  // Go to the next record as long as records exist in the stream
  if RecordStream.NumRecs <> 0 then
  begin
    RecordStream.NextRec;
    ShowCurrentRecord;
  end;
end;

procedure TMainForm.btnLastClick(Sender: TObject);
begin
  { Go to the last record in the stream as long as there are records
    in the stream }
  if RecordStream.NumRecs <> 0 then
  begin
    RecordStream.Last;
    ShowCurrentRecord;
  end;
end;

procedure TMainForm.btnPrevClick(Sender: TObject);
begin
  { Go to the previous record in the stream as long as there are records
    in the stream }
  if RecordStream.NumRecs <> 0 then
  begin
    RecordStream.PreviousRec;
    ShowCurrentRecord;
  end;
end;

procedure TMainForm.btnClearClick(Sender: TObject);
begin
  // Clear all controls on the form
  edtFirstName.Text := '';
  edtLastName.Text  := '';
  edtMI.Text        := '';
  meAge.Text        := '';
end;

end.