In Flutter how can I execute a function/method when the user starts scrolling?

Question

I have a UI with a list of size-changing widgets. I have their controllers to stop them from changing and make them all with only one size.

I have them being built inside a ListView.builder, so I would like when my user starts scrolling, all of my widgets shrink so I could give the itemExtent parameter to the ListView.builder so the scrolling performs better.

Answer 1

You can use the NotificationListener<ScrollNotification> to watch when your widget is being scrolled. Example:

return NotificationListener<ScrollNotification>(
      onNotification: (scrollNotification) {
        if (scrollNotification is ScrollStartNotification) {
          // do something when it starts scrolling
        } else if (scrollNotification is ScrollUpdateNotification) {
          // do something else, or nothing
        } else if (scrollNotification is ScrollEndNotification) {
          // do something when it stops scrolling
        }
        return false;
      },
      child: ListView.builder(
        itemCount: 20,
        itemBuilder: (_, index) {
          return ListTile(
            title: Text('Item $index'),
          );
        },
      ),
    );