缺少[Route：showbilling] [URI：{locale} / projects / {id} / billings]所需的参数

I think this is the last problem of my project. I have 2 parameters in 1 route {locale}/projects/{id}/billings , the problem is i passed 2 parameter values in view but it still prompts an error with missing required parameters. Here's my code

web.php

Route::group(['prefix' => '{locale}', 'where' => ['locale' => '[a-zA-Z]{2}'], 'middleware' => 'setlocale'], function () {

    Route::get('/', function () {

    return view('welcome');
    })->name('main');

    Auth::routes();

    Route::get('/home', 'HomeController@index')->name('home');

    //Customers
    Route::get('/customers', 'CustomerController@showcust')->name('customers');
    Route::post('/sendcust', 'CustomerController@sendcust')->name('sendcust');


    //Items
    Route::get('/items', 'ItemController@showitems')->name('items');
    Route::post('/senditem', 'ItemController@senditem')->name('senditem');

    //Projects
    Route::get('/projects', 'ProjectController@showprojects')->name('projects');
    Route::post('/sendproj', 'ProjectController@sendproj')->name('sendproj');
    //ProjectBillings
    Route::get('/projects/{id}/billings', 'ProjectController@showbilling')->name('showbilling');
    Route::post('/sendbilling', 'ProjectController@addbilling')->name('sendbilling');   

    //Invoices
    Route::get('/invoices', 'InvoiceController@showinvoice')->name('invoices');
    Route::post('/sendinvoitem', 'InvoiceController@sendinvoitem')->name('sendinvoitem');
    Route::get('/invoices/{id}/details', 'InvoiceController@showdetails');
    Route::post('/updateitem','InvoiceController@updatedetail')->name('updateitem');
    Route::get('invoices/{id}/generate', 'InvoiceController@generate');
    Route::post('/updatestatus', 'InvoiceController@changestatus')->name('updatestatus');

});

projects.blade.php

<a href="{{route('showbilling', ['locale' => app()->getLocale(), 'id' => $cat->id])}}" class="btn btn-default btn-xs waves-effect waves-float waves-green"> {{__('Add Billing')}} </a>

ProjectController.php

public function showbilling($locale, $id){
   $billings = Project::find($id);
   //return $billings;
   return view('admin.addbillings', compact('billings'));
}

UPDATE

You are passing the parameters incorrectly to the route, The error you are getting is generated at the Router method not at the controller, setting up the router method correctly, it should fix your issue.

Route::prefix('{locale}')->middleware('setlocale')->group(function(){
    Route::get('/projects/{id}/billings', 'ProjectController@showbilling')->name('showbilling');
})->where('locale' => '[a-zA-Z]{2}');

Resultant URI /{locale}/project/{id}/billings

I think you should use this URL:/{locale}/showbilling (Eg:"as/showbilling") instead now you use. The {locale} is efficient in router group. So, I guess you forget this one.