Refresh indicator doesn’t work when list doesn’t fill the whole page

Set the physics to AlwaysScrollableScrollPhysics just like the below code.

new RefreshIndicator(
    key: _refreshIndicatorKey,
    color: Colors.blue,
    onRefresh: (){
        setState(() {
            _future = fetchPosts(http.Client()); 
            _getAvalailableSlots();
        });
    },
    child: ListView.builder(
        physics: AlwaysScrollableScrollPhysics(),
        itemCount: data.length,
        itemBuilder: (context, i) {
            //do something
        }
    )
)