flutter:将FAB click listener传递到Tabbar小部件

import 'package:flutter/material.dart';

void main() {
  runApp(MyApp());
}

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      home: DefaultTabController(
        length: 3,
        child: Scaffold(
          appBar: AppBar(
            bottom: TabBar(
              tabs: [
                Tab(icon: Icon(Icons.directions_car)),
                Tab(icon: Icon(Icons.directions_transit)),
                Tab(icon: Icon(Icons.directions_bike)),
              ],
            ),
          ),
          body: TabBarView(
            children: [
              Center(child: Text('Car Page')),
              Center(child: Text('Transit Page')),
              Center(child: Text('Bike Page')),
            ],
          ),
          floatingActionButton: FloatingActionButton(
            onPressed: () {
              // 这里可以调用传递下来的点击事件处理器
              print('FAB clicked!');
            },
            child: Icon(Icons.add),
          ),
        ),
      ),
    );
  }
}