创建用于管理员登录和用户登录的中间件时，页面无法正确重定向

Question

我要创建管理员登录系统和用户登录系统。两者都有不同的表。对于用户身份验证，我使用普通身份验证，对于管理员身份验证，我使用中间件。我的代码在下面，请告诉我这段代码是什么错误

// RedirectIfNotAdmin

public function handle($request, Closure $next, $guard = 'admin')
{
    if (!Auth::guard($guard)->check()) {
        return redirect('/admin');
    }
    return $next($request);
}

路线

Route::group(['middleware' => ['web']], function () {
Route::get('admin/login', array('as' => 'login.index', 'uses' => 'Admin\LoginController@showLoginForm'));
Route::post('admin/login', array('as' => 'login.entry', 'uses' => 'Admin\LoginController@login'));
Route::get('/admin/logout','Admin\LoginController@logout');
Route::get('admin/register', 'Admin\RegisterController@showRegistrationForm');
Route::post('admin/register', 'Admin\RegisterController@register');
Route::get('/admin', 'AdminController@index');

});

内核

protected $routeMiddleware = [
    'auth' => \Illuminate\Auth\Middleware\Authenticate::class,
    'auth.basic' => \Illuminate\Auth\Middleware\AuthenticateWithBasicAuth::class,
    'bindings' => \Illuminate\Routing\Middleware\SubstituteBindings::class,
    'cache.headers' => \Illuminate\Http\Middleware\SetCacheHeaders::class,
    'can' => \Illuminate\Auth\Middleware\Authorize::class,
    'guest' => \App\Http\Middleware\RedirectIfAuthenticated::class,
    'signed' => \Illuminate\Routing\Middleware\ValidateSignature::class,
    'throttle' => \Illuminate\Routing\Middleware\ThrottleRequests::class,
    'admin' => \App\Http\Middleware\RedirectIfNotAdmin::class,
];

管理控制器

class AdminController extends Controller{
public function __construct(){
    $this->middleware('admin');
}
public function index(){
    return view('home');
}}

登录控制器

protected $redirectTo = '/admin';
public $guard = 'admin';

public function showLoginForm()
{
    if (view()->exists('admin.auth.authenticate')) {
        return view('admin.auth.authenticate');
    }

    return view('admin.auth.login');
}
public function showRegistrationForm()
{
    return view('admin.auth.register');
}