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使用Flutter开发一款电影APP

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。

App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: '/',
    );
  }
}
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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MaterialApponGenerateRoute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());
  }
}
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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),
        ],
      ),
    );
  }
}

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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]),
      ),
    );
  }
}

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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']),
                  ],
                ),
              ),
            ),
    );
  }
}

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在详情页面中,我们封装了一些组件,这样能让项目更加容易阅读和维护,组件的具体实现就不详细介绍了,都是一些常用的原生组件,这些组件分别是:

  • widgets/detail/detailTop.dart 页面顶部的电影概述
  • widgets/detail/rateing.dart 评分组件
  • widgets/detail/actors.dart 演员表
  • widgets/detail/photos.dart 剧照
  • widgets/detail/comments.dart 评论组件

真实数据来自哪里?

应用中的数据都是从豆瓣开发者api中拉取的,分别是,正在热映in_theaters,top250top250和电影详情subject/id三个接口,请求这些接口是需要apikey的,为了大家能方便请求数据,我将apikey上传到了github上,还请大家温柔点,不要将这个apikey干爆了。

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