gd_async_button.dart

import 'package:flutter/material.dart';
import 'gd_button.dart';

class GdAsyncButton extends StatefulWidget {

  final Widget child;
  final Color color;
  final bool flat;
  final bool disabled;
  final Future Function() onPressed;

  GdAsyncButton(this.child, this.onPressed, {this.color, this.flat: false, this.disabled: false});

  @override
  State<StatefulWidget> createState() => _ButtonState();
}

class _ButtonState extends State<GdAsyncButton> {
  bool working;

  @override
  void initState() {
    super.initState();
    working = false;
  }

  void onPressed() => setState(() {
    working = true;
    widget.onPressed().whenComplete(() => setState(()=> working = false));
  });

  @override
  Widget build(BuildContext context) => working ?
  Center(child: CircularProgressIndicator()) :
  GdButton.from(
    widget.child,
    onPressed,
    disabled: widget.disabled,
    color: widget.color,
    flat: widget.flat
  );
}

gd_refreshable.dart

import 'package:flutter/material.dart';
import 'gd_spin_future_builder.dart';

class GdRefreshable<T> extends StatefulWidget {
  final Future<T> Function() load;
  final Widget Function(BuildContext, T, void Function() refresh) builder;

  GdRefreshable(this.load, this.builder);

  @override
  State<StatefulWidget> createState() => _GdRefreshableState<T>();
}

class _GdRefreshableState<T> extends State<GdRefreshable<T>> {
  Future<T> loading;

  @override
  void initState() {
    super.initState();
    loading = widget.load();
  }

  @override
  Widget build(BuildContext context) => GdSpinFutureBuilder<T>(
    loading,
      (context, data) => widget.builder(
      context,
      data,
        () => setState(() {loading = widget.load();}))
  );
}

gd_spin_future_builder.dart

import 'package:flutter/material.dart';

import '../exception/invalid_token_exception.dart';

typedef Builder<T> = Widget Function(BuildContext, T);

class GdSpinFutureBuilder<T> extends StatelessWidget {
  final Future<T> future;
  final Builder<T> builder;

  GdSpinFutureBuilder(this.future, this.builder);

  @override
  Widget build(BuildContext _) => FutureBuilder(
    future: future,
    builder: (context, snapshot) {
      if(snapshot.hasError) {
        if(snapshot.error is InvalidTokenException) {
          //NOTE: this is a potential source of bugs, see https://github.com/flutter/flutter/issues/16218 for discussion
          //It may be better to handle this by wrapping the future above (currently line 15) with a .catch that handles InvalidTokenException only
          print("Your login has expired ${snapshot.error}");
          Future<void>.microtask(() {
            Navigator.pushNamedAndRemoveUntil(_, "/", (r) => false);
          });
        }
        return Center(child:Text(
          "Error: ${snapshot.error}",
          style: TextStyle(color: Colors.red),)
        );
      } else if (snapshot.hasData) {
        return builder(context, snapshot.data);
      } else {
        return Center(child: CircularProgressIndicator());
      }
    },
  );
}