laravel 5.4 session app setlocale not working

Question

In my application , I'm trying to update locale in app file like this : In Locale Middleware file :

public function handle($request, Closure $next) 
{
    if(Session::has('locale')) 
    {
        $locale = Session::get('locale'); 
        App::setLocale($locale); 
    }
    return $next($request);
}

but, it not working

I register Kernel.php already

protected $middleware = [
    \Illuminate\Foundation\Http\Middleware\CheckForMaintenanceMode::class,
    \Illuminate\Foundation\Http\Middleware\ValidatePostSize::class,
    \App\Http\Middleware\TrimStrings::class,
    \Illuminate\Foundation\Http\Middleware\ConvertEmptyStringsToNull::class,
    \App\Http\Middleware\LanguageChange::class,

];

and I create route web

Route::get('lang/{locale}', function ($locale) {
//App::setLocale($locale);
Session::put('locale', $locale); 
return Redirect::back(); 

});

My blade

<li class="dropdown">
          <a class=" dropdown-toggle" id="dropdownLang"
                           data-toggle="dropdown" aria-haspopup="true" aria-expanded="true">
                            @if(\Illuminate\Support\Facades\Session::get('locale') == "th")
                                THAI
                            @elseif(\Illuminate\Support\Facades\Session::get('locale') == "en")
                                English
                            @endif
                            <span class="caret"></span></a>
                        <ul class="dropdown-menu" aria-labelledby="dropdownLang">
                            <li>
                                <a href="{{url('lang/en')}}">
                                    ภาษาอังกฤษ (English)
                                </a>
                            </li>
                            <li>
                                <a href="{{url('lang/th')}}">
                                    ภาษาไทย (Thai)
                                </a>
                            </li>
                        </ul>
                    </li>

Answer 1

I think you should include your middleware after the 'StartSession' middleware.

protected $middlewareGroups = [
    ...
    'web' => [
        ...
        \Illuminate\Session\Middleware\StartSession::class,
        \App\Http\Middleware\Locale::class,
        ...
    ],
    ...
];

Check here to see an example in laravel 5.7 https://gist.github.com/ricardocanelas/08bec2e801226af4fe8e3180a8de466d