Laravel 5.4 migrate key is too long error

when I run migrate command with laravel 5.4 I get an error "specific key was too long", I searched and found many people also face this error. The common is add Schema::defaultStringLength(191); in AppServiceProvider.php. But the doc http://ift.tt/2jcMcjh says it is for those mysql version older than 5.7.7. But my version is 5.7.14(mysql Ver 14.14 Distrib 5.7.14, for Win64 (x86_64)), and I already set mysql default charset to utf8mb4(show variables like "%char%"):

So I think I do not need to change anything but I still get the problem. It makes me confused. Who can help me? Thanks.

via Chebli Mohamed