packages/firebase_analytics/example/lib/tabs_page.dart

// Copyright 2017 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

import 'package:flutter/material.dart';
import 'package:firebase_analytics/observer.dart';

class TabsPage extends StatefulWidget {
  static const String routeName = '/tab';

  TabsPage(this.observer);

  final FirebaseAnalyticsObserver observer;

  @override
  State<StatefulWidget> createState() => new _TabsPageState(observer);
}

class _TabsPageState extends State<TabsPage>
    with SingleTickerProviderStateMixin, RouteAware {
  _TabsPageState(this.observer);

  final FirebaseAnalyticsObserver observer;
  TabController _controller;
  int selectedIndex = 0;

  final List<Tab> tabs = <Tab>[
    const Tab(text: 'LEFT'),
    const Tab(text: 'RIGHT'),
  ];

  @override
  void didChangeDependencies() {
    super.didChangeDependencies();
    observer.subscribe(this, ModalRoute.of(context));
  }

  @override
  void dispose() {
    observer.unsubscribe(this);
    super.dispose();
  }

  @override
  void initState() {
    super.initState();
    _controller = new TabController(
      vsync: this,
      length: tabs.length,
      initialIndex: selectedIndex,
    );
    _controller.addListener(() {
      setState(() {
        if (selectedIndex != _controller.index) {
          selectedIndex = _controller.index;
          _sendCurrentTabToAnalytics();
        }
      });
    });
  }

  @override
  Widget build(BuildContext context) {
    return new Scaffold(
      appBar: new AppBar(
        bottom: new TabBar(
          controller: _controller,
          tabs: tabs,
        ),
      ),
      body: new TabBarView(
        controller: _controller,
        children: tabs.map((Tab tab) {
          return new Center(child: new Text(tab.text));
        }).toList(),
      ),
    );
  }

  @override
  void didPush() {
    _sendCurrentTabToAnalytics();
  }

  @override
  void didPopNext() {
    _sendCurrentTabToAnalytics();
  }

  void _sendCurrentTabToAnalytics() {
    observer.analytics.setCurrentScreen(
      screenName: '${TabsPage.routeName}/tab$selectedIndex',
    );
  }
}