在Wordpress插件激活时执行代码

I am building Wordpress plugin using autoloader approach. Upon plugin activation I am trying to display a simple notice. Currently, nothing is displayed upon the activation. I would appreciate any help. I have the following 2 files:

Plugin core file:

if ( ! defined( 'ABSPATH' ) ) {
   return;
}

require plugin_dir_path( __FILE__ ) . 'vendor/autoload.php';

use Acme\Class_Name;

function activator() {
    Class_Name::activate();
}

register_activation_hook( __FILE__ , 'activator' );

Class File:

namespace Acme;

class Class_Name {

    public static function activate() {
        add_action( 'admin_notices', array( __CLASS__, 'sample_admin_notice' ) );
    }

    private static function sample_admin_notice() {
    ?>
    <div class="notice notice-success is-dismissible">
        <p><?php _e( 'Done!', 'sample-text-domain' ); ?></p>
    </div>
    <?php
    }
}

Note: I configured my composer.json file and the class can be used in my core plugin file.