如何使用Flutter开发一款电影APP详解

来源：jb51　　时间：2019/7/22 10:25:49　　对本文有异议

前言

使用Flutter开发一款App是一件非常愉快的事情，其出色的性能、跨多端以及数量众多的原生组件都是我们选择Flutter的理由！今天我们就来使用Flutter开发一款电影类的App，先看下App的截图。

从main.dart开始

在Flutter里main.dart是应用开始的地方:

import 'package:flutter/material.dart';
import 'package:movie/utils/router.dart' as router;
 
void main() => runApp(MyApp());
 
class MyApp extends StatelessWidget {
 // This widget is the root of your application.
 @override
 Widget build(BuildContext context) {
  return MaterialApp(
   debugShowCheckedModeBanner: false,
   title: '电影',
   theme: ThemeData(
    primarySwatch: Colors.blue,
   ),
   onGenerateRoute: router.generateRoute,
   initialRoute: '/',
  );
 }
}

一般的，在Flutter中管理路由有两种方式，一种是直接使用Navigator.of(context).push()，这种方式比较适合非常简单的应用，随着应用的不断发展，逻辑越来越多，推荐使用具名路由来管理应用，本文也是使用的这种方式。直接将路由挂在MaterialApp的onGenerateRoute字段上即可，具体的路由定义放在了单独的文件中进行管理utils/router.dart:

import 'package:flutter/material.dart';
import 'package:movie/screens/home.dart';
import 'package:movie/screens/detail.dart';
import 'package:movie/screens/videoPlayer.dart';
 
Route<dynamic> generateRoute(RouteSettings settings) {
 switch (settings.name) {
  case '/':
   return MaterialPageRoute(builder: (context) => Home());
  case 'detail':
   var arguments = settings.arguments;
   return MaterialPageRoute(
     builder: (context) => MovieDetail(id: arguments));
  case 'video':
   var arguments = settings.arguments;
   return MaterialPageRoute(
     builder: (context) => VideoPage(url: arguments));
  default:
   return MaterialPageRoute(builder: (context) => Home());
 }
}

真是像极了前端的路由定义，先将组件import进来，然后在各自的路由中return即可。

首页

在首页中使用TabBar来展示"正在热映"和"TOP250":

import 'package:flutter/material.dart';
import 'package:movie/screens/hot.dart';
 
class Home extends StatefulWidget {
 Home({Key key}) : super(key: key);
 
 _HomeState createState() => _HomeState();
}
 
class _HomeState extends State<Home> with SingleTickerProviderStateMixin {
 TabController _tabController;
 
 @override
 void initState() {
  super.initState();
  _tabController = TabController(vsync: this, initialIndex: 0, length: 2);
 }
 
 @override
 Widget build(BuildContext context) {
  return Scaffold(
   appBar: AppBar(
    title: TabBar(
     controller: _tabController,
     tabs: <Widget>[
      Tab(text: '正在热映'),
      Tab(text: 'TOP250'),
     ],
    ),
   ),
   body: TabBarView(
    controller: _tabController,
    children: <Widget>[
     Hot(),
     Hot(history: true),
    ],
   ),
  );
 }
}

两个页面的布局是一样的，只有数据是不同的，所以我们复用这个页面Hot,传入history参数来代表是否为Top250页面

复用的Hot组件

在这个组件中，通过history字段来区分成两个页面。
在页面initState的生命周期中，请求数据，再进行相应的展示。
下拉刷新的功能是使用的RefreshIndicator组件，在其onRefresh中进行下拉时的逻辑处理。
Flutter没有直接提供上拉加载的组件，但是也是很容易实现，通过ListView的controller来做判断即可：当前滚动的位置是否到达最大滚动位置_scrollController.position.pixels == _scrollController.position.maxScrollExtent
为了获得良好的用户体验，Tab来回切换的时候，我们不希望页面重新渲染，Flutter提供了混入类AutomaticKeepAliveClientMixin，重载wantKeepAlive即可，下面是完整的代码:

import 'package:flutter/material.dart';
import 'package:movie/utils/api.dart' as api;
import 'package:movie/widgets/movieItem.dart';
 
class Hot extends StatefulWidget {
 final bool history;
 Hot({Key key, this.history = false}) : super(key: key);
 
 _HotState createState() => _HotState();
}
 
class _HotState extends State<Hot> with AutomaticKeepAliveClientMixin {
 List _movieList = [];
 int start = 0;
 int total = 0;
 ScrollController _scrollController = ScrollController();
 
 @override
 void initState() {
  super.initState();
  _scrollController.addListener(() {
   if (_scrollController.position.pixels ==
     _scrollController.position.maxScrollExtent) {
    getMore();
   }
  });
  this.query(init: true);
 }
 
 query({bool init = false}) async {
  Map res = await api.getMovieList(
    history: widget.history, start: init ? 0 : this.start);
  var start = res['start'];
  var total = res['total'];
  var subjects = res['subjects'];
  setState(() {
   if (init) {
    this._movieList = subjects;
   } else {
    this._movieList.addAll(subjects);
   }
   this.start = start + 10;
   this.total = total;
  });
 }
 
 Future<Null> _onRefresh() async {
  await this.query(init: true);
 }
 
 getMore() {
  if (start < total) {
   query();
  }
 }
 
 @override
 bool get wantKeepAlive => true;
 
 @override
 Widget build(BuildContext context) {
  super.build(context);
  return RefreshIndicator(
   onRefresh: _onRefresh,
   child: ListView.builder(
    controller: _scrollController,
    itemCount: this._movieList.length,
    itemBuilder: (BuildContext context, int index) =>
      MovieItem(data: this._movieList[index]),
   ),
  );
 }
}

电影的详情页面

点击单条电影时使用Navigator.pushNamed(context, 'detail', arguments: data['id']);即可跳转详情页，在详情页中通过id再请求接口获取详情:

import 'package:flutter/material.dart';
import 'package:movie/widgets/detail/detailTop.dart';
import 'package:movie/widgets/detail/rateing.dart';
import 'package:movie/widgets/detail/actors.dart';
import 'package:movie/widgets/detail/photos.dart';
import 'package:movie/widgets/detail/comments.dart';
import 'package:movie/utils/api.dart' as api;
 
class MovieDetail extends StatefulWidget {
 final id;
 MovieDetail({Key key, this.id}) : super(key: key);
 
 _MovieDetailState createState() => _MovieDetailState();
}
 
class _MovieDetailState extends State<MovieDetail> {
 var _data = {};
 
 @override
 void initState() {
  super.initState();
  this.init();
 }
 
 init() async {
  var res = await api.getMovieDetail(widget.id);
  setState(() {
   _data = res;
  });
 }
 
 @override
 Widget build(BuildContext context) {
  return Scaffold(
   body: _data.isEmpty
     ? Center(child: CircularProgressIndicator(),)
     : SafeArea(
       child: Container(
        height: MediaQuery.of(context).size.height,
        width: MediaQuery.of(context).size.width,
        child: ListView(
         scrollDirection: Axis.vertical,
         children: <Widget>[
          MovieDetailTop(data: _data),
          Rate(count: _data['ratings_count'], rating: _data['rating']),
          Container(padding: EdgeInsets.all(10),child: Text(_data['summary'])),
          Actors(directors: _data['directors'], casts: _data['casts']),
          Photos(photos: _data['photos'],),
          Comments(comments: _data['popular_comments']),
         ],
        ),
       ),
      ),
  );
 }
}