前言

Flutter是一款移动应用程序SDK，一份代码可以同时生成iOS和Android两个高性能应用程序能提高开发效率，在应用程序运行时更改代码并重新加载，提供的丰富的Material Design(Android)和Cupertino(iOS风格)等优点。看到此处我们是不是很想加入flutter开发中呢？但是目前 flutter 框架还比较新，有些功能还是需要原生去实现，那我们该怎样选择呢？下面带你进入混编之旅。

准备工作

1.混编的前提是你的电脑必须有 flutter 环境，可以参考Flutter中文网。
2.一个Xcode项目。
3.三方管理平台CocoaPods。

创建flutter模块

因为使用flutter模块需要跨平台，所以需要在项目根目录创建一个和项目目录平级的模块，比如项目目录是some/path/MyApp,那么你需要在some/path目录项创建flutter模块。

cd some/path
flutter create -t module my_flutter

依赖引入

我们开发中大多使用CocoaPods管理第三方和依赖。在项目中引入flutter模块，就需要引入flutter依赖库。在pod配置文件中加入以下代码，然后执行pod install。

flutter_application_path = '../my_flutter/'
eval(File.read(File.join(flutter_application_path, '.ios', 'Flutter', 'podhelper.rb')), binding)

这时我们的flutter模块以及依赖环境已经全部配置好了。我们想用iOS项目去调用flutter还是做不到，需要在Xcode里面配置一些信息。

Xcode配置

flutter和iOS混合开发是不支持BitCode的，所以我们需要把它设置为NO。

屏幕快照 2019-07-05 15.51.46.png

在iOS工程里面添加运行脚本

"$FLUTTER_ROOT/packages/flutter_tools/bin/xcode_backend.sh" build

"$FLUTTER_ROOT/packages/flutter_tools/bin/xcode_backend.sh" embed

修改项目代码

1.将AppDelegate的头文件改成

#import <UIKit/UIKit.h>
#import <Flutter/Flutter.h>
@interface AppDelegate : FlutterAppDelegate
@property (strong, nonatomic) UIWindow *window;
@end

2.在AppDelegate的实现文件的didFinishLaunchingWithOptions方法中添加

[GeneratedPluginRegistrant registerWithRegistry:self];

综上所述flutter模块已经集成到我们iOS项目中了，代码运行也没有问题，那我们怎样才能在iOS中调用flutter界面呢？怎样让他们进行交互呢？

#import <Flutter/Flutter.h>
#import "ViewController.h"

@implementation ViewController
- (void)viewDidLoad {
    [super viewDidLoad];
    UIButton *button = [UIButton buttonWithType:UIButtonTypeCustom];
    [button addTarget:self
               action:@selector(handleButtonAction)
     forControlEvents:UIControlEventTouchUpInside];
    [button setTitle:@"Press me" forState:UIControlStateNormal];
    [button setBackgroundColor:[UIColor blueColor]];
    button.frame = CGRectMake(80.0, 210.0, 160.0, 40.0);
    [self.view addSubview:button];
}
- (void)handleButtonAction {
    FlutterViewController* flutterViewController = [[FlutterViewController alloc] init];
//此处是设置路由跳转的
    [flutterViewController setInitialRoute:@"myApp"];
    [self presentViewController:flutterViewController animated:false completion:nil];
}
@end

在flutter中怎样才能响应这个调用呢？

 switch (route) {
    case 'myApp':
      return new MyApp();
    default:
      return Center(
        child: Text('Unknown route: $route', textDirection: TextDirection.ltr),
      );

这样就可以从iOS原生跳转到flutter界面了，运行APP点击按钮就会出现下面的界面。

屏幕快照 2019-07-05 16.37.04.png

这种界面肯定不符合我们开发的需求，iOS原生和flutter都有一个导航栏，那我们就需要隐藏一个。
隐藏iOS原生导航

[self.navigationController setNavigationBarHidden:YES animated:NO];

但是使用flutter的导航，点击返回的时候比较麻烦，需要监听flutter点击事件，在调用iOS原生的返回，代码处理在下方。
隐藏flutter导航

将图中选中的部分删除

运行之后界面清爽多了，但是还有一个DEBUG标志，可以使用一下代码去掉

 debugShowCheckedModeBanner: false, // 去除debug旗标

iOS与flutter的数据传输怎么做呢？代码参考

   // 创建FlutterViewController，并跳转到Flutter页面
    FlutterViewController* flutterViewController = [[FlutterViewController alloc] init];
    // 设置路由名字 跳转到不同的flutter界面
    [flutterViewController setInitialRoute:@"myApp"];
    __weak __typeof(self) weakSelf = self;
    // 要与main.dart中一致
    NSString *channelName = @"com.pages.your/native_get";
    
    FlutterMethodChannel *messageChannel = [FlutterMethodChannel methodChannelWithName:channelName binaryMessenger:flutterViewController];
    
    [messageChannel setMethodCallHandler:^(FlutterMethodCall * _Nonnull call, FlutterResult  _Nonnull result) {
        // call.method 获取 flutter 方法名
        // call.arguments 获取到 flutter 给到的参数
        // result 是给flutter的回调， 该回调只能使用一次
        NSLog(@"method=%@ \narguments = %@", call.method, call.arguments);
        if ([call.method isEqualToString:@"iOSFlutter"]) {
            //如果隐藏iOS原生方法，需要做f返回处理
            [self.navigationController popViewControllerAnimated:YES];
        }
        // flutter传参给iOS
        if ([call.method isEqualToString:@"iOSFlutter1"]) {
            NSDictionary *dic = call.arguments;
            NSLog(@"arguments = %@", dic);
        }
        // iOS给flutter返回值
        if ([call.method isEqualToString:@"iOSFlutter2"]) {
            if (result) {
                result(@"返回给flutter的内容");
            }
        }
    }];
    
    [self.navigationController pushViewController:flutterViewController animated:YES];

在flutter中的代码

import 'dart:ui' as ui; // 调用window拿到route判断跳转哪个界面
import 'package:flutter/material.dart';
import 'package:flutter/services.dart';
//import 'package:flutter_module/HomePage.dart';


void main() => runApp(_widgetForRoute(ui.window.defaultRouteName));

// 根据iOS端传来的route跳转不同界面
Widget _widgetForRoute(String route) {
  switch (route) {
    case 'myApp':
      return new MyApp();
    case 'home':
      return new MyApp();
    default:
      return Center(
        child: Text('Unknown route: $route', textDirection: TextDirection.ltr),
      );
  }
}

class MyApp extends StatelessWidget {

  Widget _home(BuildContext context) {
    return new MyHomePage(title: 'Flutter Demo Home Page');
  }

  @override
  Widget build(BuildContext context) {
    return new MaterialApp(
      title: 'Flutter Demo',
      theme: new ThemeData(
        primarySwatch: Colors.blue,
      ),
      routes: <String, WidgetBuilder>{
        "/home":(BuildContext context) => new MyApp(),
      },
      home: _home(context),
    );
  }
}

class MyHomePage extends StatefulWidget {
  MyHomePage({Key key, this.title}) : super(key: key);

  final String title;

  @override
  _MyHomePageState createState() => new _MyHomePageState();
}

class _MyHomePageState extends State<MyHomePage> {

  // 创建一个给native的channel (类似iOS的通知）
  static const methodChannel = const MethodChannel('com.pages.your/native_get');


  //
  _iOSPushToVC() async {
    await methodChannel.invokeMethod('iOSFlutter', '参数');
  }

  _iOSPushToVC1() async {
    Map<String, dynamic> map = {"code": "200", "data":[1,2,3]};
    await methodChannel.invokeMethod('iOSFlutter1', map);
  }

  _iOSPushToVC2() async {
    dynamic result;
    try {
      result = await methodChannel.invokeMethod('iOSFlutter2');
    } on PlatformException {
      result = "error";
    }
    if (result is String) {
      print(result);
      showModalBottomSheet(context: context, builder: (BuildContext context) {
        return new Container(
          child: new Center(
            child: new Text(result, style: new TextStyle(color: Colors.brown), textAlign: TextAlign.center,),
          ),
          height: 40.0,
        );
      });
    }
  }

  @override
  Widget build(BuildContext context) {
    return new Scaffold(
      body: new Center(
        child: new Column(
          mainAxisAlignment: MainAxisAlignment.center,
          children: <Widget>[
            new FlatButton(onPressed: () {
              _iOSPushToVC();
            }, child: new Text("跳转ios新界面，参数是字符串")),
            new FlatButton(onPressed: () {
              _iOSPushToVC1();
            }, child: new Text("传参，参数是map，看log")),
            new FlatButton(onPressed: () {
              _iOSPushToVC2();
            }, child: new Text("接收客户端相关内容")),
          ],
        ),
      ),
    );
  }
}

那我们怎样在初始化flutter界面时候iOS传值给flutter呢？

#import "TargetViewController.h"
#import <Flutter/Flutter.h>

@interface TargetViewController () <FlutterStreamHandler>

@end

@implementation TargetViewController

- (void)viewDidLoad {
    [super viewDidLoad];
    self.title = @"TargetViewController";
    self.view.backgroundColor = [UIColor whiteColor];
}

- (void)didReceiveMemoryWarning {
    [super didReceiveMemoryWarning];
    // Dispose of any resources that can be recreated.
}

- (void)pushFlutterViewController_EventChannel {
    FlutterViewController* flutterViewController = [[FlutterViewController alloc] initWithProject:nil nibName:nil bundle:nil];
    flutterViewController.navigationItem.title = @"Demo";
    [flutterViewController setInitialRoute:@"home"];
    // 要与main.dart中一致
    NSString *channelName = @"com.pages.your/native_post";
    
    FlutterEventChannel *evenChannal = [FlutterEventChannel eventChannelWithName:channelName binaryMessenger:flutterViewController];
    // 代理FlutterStreamHandler
    [evenChannal setStreamHandler:self];
    
    [self.navigationController pushViewController:flutterViewController animated:YES];
}

#pragma mark - <FlutterStreamHandler>
// // 这个onListen是Flutter端开始监听这个channel时的回调，第二个参数 EventSink是用来传数据的载体。
- (FlutterError* _Nullable)onListenWithArguments:(id _Nullable)arguments
                                       eventSink:(FlutterEventSink)events {
    // arguments flutter给native的参数
    // 回调给flutter， 建议使用实例指向，因为该block可以使用多次
    if (events) {
        events(@"push传值给flutter的vc");
    }
    return nil;
}
/// flutter不再接收
- (FlutterError* _Nullable)onCancelWithArguments:(id _Nullable)arguments {
    // arguments flutter给native的参数
    NSLog(@"%@", arguments);
    return nil;
}
- (void)touchesBegan:(NSSet<UITouch *> *)touches withEvent:(UIEvent *)event {
    [self pushFlutterViewController_EventChannel];
}
@end

import 'package:flutter/material.dart';
import 'package:flutter/services.dart';

class HomePage extends StatefulWidget {
  _HomePageState createState() => _HomePageState();
}

class _HomePageState extends State<HomePage> {

  // 注册一个通知
  static const EventChannel eventChannel = const EventChannel('com.pages.your/native_post');

  // 渲染前的操作，类似viewDidLoad
  @override
  void initState() {
    super.initState();

    // 监听事件，同时发送参数12345
    eventChannel.receiveBroadcastStream(12345).listen(_onEvent,onError: _onError);
  }

  String naviTitle = 'title' ;
  // 回调事件
  void _onEvent(Object event) {
    setState(() {
      naviTitle =  event.toString();
    });
  }
  // 错误返回
  void _onError(Object error) {

  }

  @override
  Widget build(BuildContext context) {
    return new MaterialApp(
      home: new Material(
        child: new Scaffold(
          body: new Center(
            child: new Text(naviTitle),
          ),
        ),
      ),
    );
  }
}