unit Unit1;
  
interface
  
uses
  Winapi.Windows, Winapi.Messages, System.SysUtils, System.Variants,
  System.Classes, Vcl.Graphics,
  Vcl.Controls, Vcl.Forms, Vcl.Dialogs, Vcl.StdCtrls, Vcl.ExtDlgs;
  
type
  TForm1 = class(TForm)
    Memo1: TMemo;
    FileOpen: TButton;
    FileSave: TButton;
    FileSaveAs: TButton;
    FileExit: TButton;
    FileNew: TButton;
    OpenDialog1: TOpenDialog;
    SaveDialog1: TSaveDialog;
    procedure FileOpenClick(Sender: TObject);
    procedure FileSaveClick(Sender: TObject);
    procedure FileExitClick(Sender: TObject);
    procedure FormCreate(Sender: TObject);
    procedure FileNewClick(Sender: TObject);
    procedure FileSaveAsClick(Sender: TObject);
    procedure FormClose(Sender: TObject; var Action: TCloseAction);
  private
    { Private declarations }
    FFileName: string;
    FUpdating: Boolean;
    FDragOfs: Integer;
    FDragging: Boolean;
    procedure CheckFileSave;
    procedure SetFileName(const FileName: String);
    procedure PerformFileOpen(const AFileName: string);
    procedure WMDropFiles(var Msg: TWMDropFiles); message WM_DROPFILES;
  public
    { Public declarations }
  end;
  
var
  Form1: TForm1;
  
implementation
  
uses ShellAPI;
{$R *.dfm}
  
resourcestring
  sSaveChanges = \'是否将未更改保存到 %s?\';
  sOverWrite = \'%s 已存在。\'+#13#10+\'要替换它吗？\';
  sTitle = \'记事本\';
  sUntitled = \'未命名\';
  sColRowInfo = \'Line: %3d   Col: %3d\';
  sCommonDlgFileName = \'文本文档(*.txt)|*.txt|所有文件(*.*)|*.*\';
  
  
procedure TForm1.CheckFileSave;
var
  SaveRespond: Integer;
begin
  if not Memo1.Modified then
    Exit;
  SaveRespond := MessageBox(Handle, PWideChar(Format(sSaveChanges, [FFileName])
    ), PWideChar(sTitle), MB_YESNOCANCEL + MB_ICONINFORMATION);
  case SaveRespond of
    idYes:
      FileSave.click;
    idNo:
      ; { Nothing }
    idCancel:
      Abort;
  end;
end;
  
procedure TForm1.SetFileName(const FileName: String);
begin
  FFileName := FileName;
  Caption := Format(\'%s - %s\', [ExtractFileName(FileName), sTitle]);
end;
  
procedure TForm1.PerformFileOpen(const AFileName: string);
begin
  Memo1.Lines.LoadFromFile(AFileName);
  SetFileName(AFileName);
  Memo1.SetFocus;
  Memo1.Modified := False;
end;
  
procedure TForm1.WMDropFiles(var Msg: TWMDropFiles);
var
  CFileName: array [0 .. MAX_PATH] of Char;
begin
  try
    if DragQueryFile(Msg.Drop, 0, CFileName, MAX_PATH) > 0 then
    begin
      CheckFileSave;
      PerformFileOpen(CFileName);
      Msg.Result := 0;
    end;
  finally
    DragFinish(Msg.Drop);
  end;
end;
  
procedure TForm1.FileNewClick(Sender: TObject);
begin
  CheckFileSave;
  SetFileName(sUntitled);
  
  Memo1.Lines.Clear;
  Memo1.Modified := False;
end;
  
procedure TForm1.FileOpenClick(Sender: TObject);
begin
  CheckFileSave;
  
  with TOpenDialog.Create(nil) do
  begin
    Filter := sCommonDlgFileName;
    FileName:=\'*.txt\';
    if Execute then
    begin
      PerformFileOpen(FileName);
      Memo1.ReadOnly := ofReadOnly in Options;
    end;
  end;
end;
  
procedure TForm1.FileSaveAsClick(Sender: TObject);
begin
  with TSaveDialog.Create(nil) do
  begin
    Filter := sCommonDlgFileName;
    FileName:=\'*.txt\';
    if Execute then
    begin
      if FileExists(FileName) then
        if MessageBox(Handle, PWideChar(Format(sOverWrite, [FFileName])),
          PWideChar(sTitle), MB_YESNOCANCEL + MB_ICONINFORMATION) <> idYes then
          Exit;
      Memo1.Lines.SaveToFile(FileName);
      SetFileName(FileName);
      Memo1.Modified := False;
    end;
  end;
end;
  
procedure TForm1.FileSaveClick(Sender: TObject);
begin
  if FFileName = sUntitled then
    FileSaveAs.click
  else
  begin
    Memo1.Lines.SaveToFile(FFileName);
    Memo1.Modified := False;
  end;
end;
  
procedure TForm1.FormClose(Sender: TObject; var Action: TCloseAction);
begin
  CheckFileSave;
end;
  
procedure TForm1.FormCreate(Sender: TObject);
begin
  SetFileName(sUntitled);
  DragAcceptFiles(Handle, True);
end;
  
procedure TForm1.FileExitClick(Sender: TObject);
begin
  Close;
end;
  
end.