unit u_frmLogin;

interface

uses Windows, SysUtils, Classes, Graphics, Forms, Controls, StdCtrls,
  Buttons, Db, ADODB,Dialogs;

type
  TfrmLogin = class(TForm)
    Label1: TLabel;
    txtPassword: TEdit;
    OKBtn: TButton;
    CancelBtn: TButton;
    Label2: TLabel;
    cmbUserName: TComboBox;
    ADOTable1: TADOTable;
    procedure CancelBtnClick(Sender: TObject);
    procedure FormCloseQuery(Sender: TObject; var CanClose: Boolean);
    procedure OKBtnClick(Sender: TObject);
    procedure FormCreate(Sender: TObject);
  private
    { Private declarations }
    bolSuccess:Boolean; //默認為False,True表示登錄成功！
    procedure ListUserName;     //列出用戶帳號到ComboBox
  public
    { Public declarations }
  end;

var
  frmLogin: TfrmLogin;

implementation

uses Main,DataModule;

{$R *.DFM}

procedure TfrmLogin.CancelBtnClick(Sender: TObject);
begin
  Close;        //退出登錄
end;

procedure TfrmLogin.FormCloseQuery(Sender: TObject; var CanClose: Boolean);
begin
  CanClose:=True;       //允許關閉登錄對話框。
  if not bolSuccess then        //退出登錄，則關閉登錄對話框，再結束程序！
    MainForm.Close;      //關閉主窗口，也就是關閉程序。
end;

procedure TfrmLogin.OKBtnClick(Sender: TObject);
begin
  {IndexOf方法從ComboBox中查找指定的文本，如果找到則返回索引值，否則返回-1}
  if cmbUserName.Items.IndexOf(cmbUserName.Text)<0 then
    ShowMessage('請選擇正確的用戶帳號！')
  else
  begin

     if not ADOTable1.Locate('Username',
        Copy(cmbUserName.Text,1,10),[]) then
     begin
       ShowMessage('找不到該帳號，請確定輸入或設置的帳號是否正確！');
       exit;    //退出該過程
     end;
     
    {比較用戶輸入的密碼！}
    if txtPassword.Text=ADOTable1.FieldByName('Password').AsString then
    begin
      bolSuccess:=True;
      Close;
    end
    else
    begin
      ShowMessage('密碼錯誤，請重新輸入！');
      {先將焦點移到別的地方，再將焦點移回密碼輸入框，就可以選中
       密碼輸入框的文本，等待輸入，這是一個秘技哦！不要說沒什么，打擊我！哼！}
      OKbtn.SetFocus;
      txtPassword.SetFocus;
    end;
  end;
end;

procedure TfrmLogin.ListUserName;
var
  i:Integer;
begin
  ADOTable1.Close;
  ADOTable1.Connection:= DataModuleADO.ADOConnection1;
  ADOTable1.TableName:='Operator'; //數據表名稱！
  ADOTable1.Open;       //打開數據庫表
  cmbUserName.Clear;    //先清空ComboBox

  for i:=0 to ADOTable1.RecordCount-1 do
  begin
    cmbUserName.Items.Add(ADOTable1.FieldByName('Username').AsString);
    ADOTable1.Next;
  end;
end;

procedure TfrmLogin.FormCreate(Sender: TObject);
begin
  ListUserName; //列出用戶帳號
end;

end.