Flutter之顶部导航栏的设计

 

import 'package:flutter/material.dart';

class TapAppBar extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      home: DefaultTabController(
        length: choices.length,//这样设计的可拓展性强
        child: Scaffold(
          appBar: AppBar(
            leading: GestureDetector(
              onTap: () {
                Navigator.pop(context);
              },
              child: Icon(Icons.arrow_back),
            ),
            title: const Text('roadkiller'),
            bottom: TabBar(
              isScrollable: false,//可滚动与否
              tabs: choices.map((Choice choice) {
                return Tab(//顶部导航栏的结构
                  text: choice.title,//文字
                  icon: Icon(choice.icon),//图标
                );
              }).toList(),//注意要转成List,因为tabs里边是children:widget[]
            ),
          ),
          body: TabBarView(//主体部分是TabView
            children:choices.map((Choice choice) {
              return Padding(//返回一个Padding
                padding: const EdgeInsets.all(16.0),
                child: ChoiceCard(
                  choice: choice,
                ),
              );
            }).toList(),//注意也是List
          ),
        ),
      ),
    );
  }
}

class Choice {
  const Choice({this.title, this.icon});

  final String title;
  final IconData icon;
}

const List<Choice> choices = const <Choice>[//可拓展性
  const Choice(title: 'Car', icon: Icons.directions_car),
  const Choice(title: 'Bike', icon: Icons.directions_bike),
  const Choice(title: 'Bus', icon: Icons.directions_bus),
  const Choice(title: 'Walk', icon: Icons.directions_walk),
  const Choice(title: 'Train', icon: Icons.directions_transit)
];

class ChoiceCard extends StatelessWidget {
  const ChoiceCard({Key key, this.choice}) : super(key: key);//继承

  final Choice choice;

  @override
  Widget build(BuildContext context) {
    return Card(
      color: Colors.white,
      child: Center(
        child: Column(
            mainAxisSize: MainAxisSize.min,//横向大小
            crossAxisAlignment: CrossAxisAlignment.center,//纵向对齐方式
            children: <Widget>[
              Icon(
                choice.icon,
                size: 128.0,
              ),
              Text(
                choice.title,
              )
            ]),
      ),
    );
  }
}