login.pas

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unit Login;

interface

uses
  Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
  Dialogs, StdCtrls, Buttons, DBTables, DB;

type
  TLoginFrm = class(TForm)
    Login_Database: TDatabase;
    Login_Table: TTable;
    Login_Query: TQuery;
    LoginPassword_Label: TLabel;
    LoginUsername_Label: TLabel;
    LoginTitle_Label: TLabel;
    LoginUsername_ComboBox: TComboBox;
    LoginPassword_Edit: TEdit;
    LoginCancel_BitBtn: TBitBtn;
    LoginOk_BitBtn: TBitBtn;
    procedure LoginOk_BitBtnClick(Sender: TObject);
    procedure LoginCancel_BitBtnClick(Sender: TObject);
    procedure FormCreate(Sender: TObject);
  private
    { Private declarations }
  public
     loginusername:string;
    { Public declarations }
  end;

var
  LoginFrm: TLoginFrm;

  function Getpassword(password:string):string;


implementation

uses MainForm;  

{$R *.dfm}


 //-------定义函数：获取数据库的用户密码（译码）------
function Getpassword(password:string):string;
var i,passwordlength:integer;
    temppassword:string;
begin
   passwordlength:=length(password);
   temppassword:='';
   for i:=passwordlength downto 1 do
       begin
          temppassword:=temppassword+copy(password,i,1);
       end;
   Getpassword:=temppassword;
end;

procedure TLoginFrm.LoginOk_BitBtnClick(Sender: TObject);
var querystring,password,loginpassword:string;
begin
    //管理员初次登陆，密码是888888
    loginusername:=LoginUsername_ComboBox.text;
    querystring:='select * from login where username='+''''+LoginUsername_ComboBox.text+'''';
    with Login_Query do
      begin
        //-------获取数据库密码------
       sql.clear;
       sql.add(querystring);
       open;
       password:=Getpassword(fieldbyname('password').asstring);
       close;
      end;
    loginpassword:=LoginPassword_Edit.text;

    //-------判断密码是否正确------
    if loginpassword=password then
          begin
            LoginFrm.hide;
            Login_Table.active:=false;
            Login_Query.active:=false;
            Login_Database.Connected:=false;
            MainFrm.show;
          end
     else
       begin
          LoginPassword_Edit.text:='000000';
          messagebox(LoginFrm.handle,'请输入正确的密码','警告',mb_ok+mb_iconwarning);
       end;
end;

procedure TLoginFrm.LoginCancel_BitBtnClick(Sender: TObject);
begin
  Login_Table.active:=false;
  Login_Query.active:=false;
  Login_Database.Connected:=false;
  LoginFrm.hide;
end;

procedure TLoginFrm.FormCreate(Sender: TObject);
begin
   Login_Table.active:=True;
   Login_Database.Connected:=True;
   LoginUsername_ComboBox.text:='administrator';
   Login_Table.first;
    //-------显示用户列表------
   while not Login_Table.eof do
      begin
       LoginUsername_ComboBox.items.insert(-1,Login_Table.fieldbyname('username').asstring);
       Login_Table.Next;
      end;
end;


end.