Tab bar view error as used the same GlobalKey multiple times

Question

I'm using Flutter. I have a simple app with 3 tabs. There is a RefreshIndicator in each tab with a ListView. The rows are built in another method. This is the code:

@override
 Widget build(BuildContext context) {
    final GlobalKey<RefreshIndicatorState> _RIKey1 = new GlobalKey<RefreshIndicatorState>();
    final GlobalKey<RefreshIndicatorState> _RIKey2 = new GlobalKey<RefreshIndicatorState>();
    final GlobalKey<RefreshIndicatorState> _RIKey3 = new GlobalKey<RefreshIndicatorState>();

    debugPrint(_RIKey1.toString());
    debugPrint(_RIKey2.toString());
    debugPrint(_RIKey3.toString());
    return new Scaffold(
      body: new DefaultTabController(
        length: 3,
        child: new Scaffold(
          appBar: new AppBar(
            actions: <Widget>[
              IconButton(
                icon: Icon(Icons.refresh),
                onPressed: () {
                      _RIKey1.currentState.show();
                    },
              )
            ],
            bottom: new TabBar(
              tabs: [
                new Tab(icon: new Icon(Icons.view_list)),
                new Tab(icon: new Icon(Icons.hotel)),
                new Tab(icon: new Icon(Icons.assessment)),
              ],
            ),
            title: new Text('Data'),
          ),
          body: new TabBarView(
            children: [
              new RefreshIndicator(
                key: _RIKey1,
                onRefresh: _actualizoData1,
                child: new ListView.builder(
                    padding: new EdgeInsets.only(top: 5.0),
                    itemCount: linea_reservas.length * 2,
                    itemBuilder: (BuildContext context, int position) {
                      if (position.isOdd) return new Divider();
                      final index = position ~/ 2;
                      return _buildRow(index);
                    }),
              ),
              new RefreshIndicator(
                key: _RIKey2,
                onRefresh: _actualizoData2,
                child: new ListView.builder(
                    padding: new EdgeInsets.only(top: 8.0),
                    itemCount: linea_inouthouse.length * 2,
                    itemBuilder: (BuildContext context, int position) {
                      if (position.isOdd) return new Divider();
                      final index = position ~/ 2;
                      return _buildRowInOutHouse(index);
                    }),
              ),
              new RefreshIndicator(
                key: _RIKey3,
                onRefresh: _actualizoData3,
                child: new ListView.builder(
                    padding: new EdgeInsets.only(top: 5.0),
                    itemCount: linea_ocupacion.length * 2,
                    itemBuilder: (BuildContext context, int position) {
                      if (position.isOdd) return new Divider();
                      final index = position ~/ 2;
                      return _buildRowOcupacion(index);
                    }),
              ),
            ],
          ),
        ),
      ),
    );
  }

the app works, but after changing tabs a few times, it crashes with this error:

I/flutter ( 5252): ══╡ EXCEPTION CAUGHT BY WIDGETS LIBRARY ╞═══════════════════════════════════════════════════════════
I/flutter ( 5252): The following assertion was thrown building NotificationListener<KeepAliveNotification>:
I/flutter ( 5252): Multiple widgets used the same GlobalKey.
I/flutter ( 5252): The key [LabeledGlobalKey<RefreshIndicatorState>#7bd42] was used by multiple widgets. The parents of
I/flutter ( 5252): those widgets were:
I/flutter ( 5252): - RepaintBoundary-[<[LabeledGlobalKey<RefreshIndicatorState>#7bd42]>](renderObject:
I/flutter ( 5252):   RenderRepaintBoundary#60a4a DETACHED)
I/flutter ( 5252): - RepaintBoundary-[<[LabeledGlobalKey<RefreshIndicatorState>#7bd42]>](renderObject:
I/flutter ( 5252):   RenderRepaintBoundary#c8cdb NEEDS-LAYOUT NEEDS-PAINT)
I/flutter ( 5252): A GlobalKey can only be specified on one widget at a time in the widget tree.

I searched online an found an StackOverflow solution Multiple widgets used the same GlobalKey to use custom keys:

import 'package:flutter/widgets.dart';

class RIKeys {
  static final riKey1 = const Key('__RIKEY1__');
  static final riKey2 = const Key('__RIKEY2__');
  static final riKey3 = const Key('__RIKEY3__');
}

Now it works as intended but I'm not sure how I can declare it on state class and show the currentState.show() when the user taps on refresh button on the app bar as below:

GlobalKey<RefreshIndicatorState> _RIKey1 = new GlobalKey<RefreshIndicatorState>();

_RIKey1.currentState.show();

I'm not sure how to overcome this issue please advise. Thank you for any help.