AdminUiBootstrap.php

<?php
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namespace yii\adminUi;
use Yii;
use yii\base\Application;
use yii\base\BootstrapInterface;
use yii\web\Controller;
use yii\base\Event;

class AdminUiBootstrap implements BootstrapInterface{
    public function bootstrap($app){
        \Yii::$classMap = array_merge(\Yii::$classMap,[
                'yii\grid\CheckboxColumn'=>'@yii/adminUi/widget/CheckboxColumn.php',
                'yii\grid\ActionColumn'=>'@yii/adminUi/widget/ActionColumn.php',
            ]);
        $app->set('view', [
            'class'=>'yii\web\View',
            'theme' => [
                'pathMap' => ['@backend/views' => '@backend/themes/adminui'],   // for Admin theme which resides on extension/adminui
                'baseUrl' => '@web/themes/adminui',
            ],
        ]);
        
        $app->setModule('adminuidemo',['class'=>'yii\adminUi\module\Module']);
        
		$app->set('assetManager' , [
			'class'	=> 'yii\web\AssetManager',
            'bundles' => [                
                'yii\bootstrap\BootstrapAsset' => [
                     'sourcePath' => null,
                     'css' => []
                ],
                'yii\bootstrap\BootstrapPluginAsset' => [
                     'sourcePath' => null,
                     'js' => []
                ],
                'yii\grid\GridViewAsset' => [
                    'depends'   => [
                        'backend\assets\AppAsset'
                    ],
                ],
				'backend\assets\AppAsset' => [
					'css'	=> [],
				],
            ],            
            'linkAssets' => true,
        ]);
        
        Event::on(Controller::className(), Controller::EVENT_BEFORE_ACTION, function ($event) {
            if($event->action->id == 'login' && in_array('backend',  explode("\\", $event->sender->className()))){
                $event->sender->layout = '//blank';
            }
        });
    }
}