I want to get effect similar as here:
Flutter includes a dropdown button, but can we add searching functionality to it? Where can I start?
Solution 1: Alireza Abiri
You should create a StatefulWidget (button for example) which its root widget is a GestureDetector, then showDialog on button tap.
Dialog should contain a list of items as state and a ListView.builder() to build items. When you search you should render items with items.where() to filter items.