一. flutter與iOS的消息傳遞

Flutter和原生交互主要通過channel進(jìn)行通信猾浦，主要包括三類（以flutter開頭的類均是原生端類）

下面以MethodChannel 和FlutterMethodChannel為例進(jìn)行說明
1. flutter端

 //1.初始化channel
 final platform = const  MethodChannel('samples.flutter.io/test');

  //2.設(shè)置回調(diào)方法
  void initState() {
    super.initState();
    platform.setMethodCallHandler(invokeFlutterMethod);
  }

  Future< Null > invokeFlutterMethod(MethodCall call) async{
    setState(() {
      content = call.arguments['text'];
    });
  }

  //3.在合適的地方（按鈕點(diǎn)擊事件）槽片，調(diào)用iOS方法
  Future _invokeIOSMethod() async {
    try {
      await platform.invokeMethod('invokeIOSMethod',{'text':'flutter傳過來的參數(shù)'});
    } on PlatformException catch (e) {    }
  }

2.iOS端

    //1.初始化FlutterViewController頁面（官方推薦方式）
    FlutterEngine *flutterEngine =
    ((AppDelegate *)UIApplication.sharedApplication.delegate).flutterEngine;
    FlutterViewController *flutterVC =
    [[FlutterViewController alloc] initWithEngine:flutterEngine nibName:nil bundle:nil];
    flutterVC.modalPresentationStyle = UIModalPresentationFullScreen;
    [self presentViewController:flutterVC animated:YES completion:nil];

    //2.初始化channel
    FlutterMethodChannel* channel = [FlutterMethodChannel
                                     methodChannelWithName:@"samples.flutter.io/test"
                                     binaryMessenger:flutterVC.binaryMessenger];

    //3.調(diào)用Flutter方法
    [channel invokeMethod:@"invokeFlutterMethod" arguments:@{@"text":@"ios傳給flutter的參數(shù)"}];

    //4.設(shè)置回調(diào)（等待Flutter調(diào)用）
    [channel setMethodCallHandler:^(FlutterMethodCall* call, FlutterResult result) {
        if ([call.method isEqualToString:@"invokeIOSMethod"]) {
            [flutterVC dismissViewControllerAnimated:YES completion:nil];
        }
    }];

二.在iOS端切換flutter頁面

?閃退？返回控制器不銷毀随橘？內(nèi)存泄漏？
?解決方案：
官方人員（Dan Field）給出了答案
通過驗(yàn)證官方的例子锦庸，現(xiàn)總結(jié)如下：
1. 使用setInitialRoute 設(shè)置flutter頁面
自己的理解：重新初始化FlutterViewController內(nèi)部會重新創(chuàng)建FlutterEngine机蔗，導(dǎo)致flutter的代碼重新加載main函數(shù)，然后通過window.defaultRouteName獲取新的路由值（這里路由值為full）甘萧，根據(jù)路由值加載對應(yīng)頁面

//FullScreenViewController繼承自FlutterViewController
  FullScreenViewController *flutterViewController =
      [[FullScreenViewController alloc] init];
  [flutterViewController setInitialRoute:@"full"];
//在交互的過程中萝嘁，官方代碼動畫過度都設(shè)置的NO，說是有問題扬卷，猜測是過渡不自然牙言，
 [self.navigationController
      pushViewController:flutterViewController
                animated:NO];

2.使用全局的FlutterEngine設(shè)置flutter頁面
實(shí)現(xiàn)過程：使用一個(gè)全局的channel來管理頁面切換，iOS通過發(fā)送channel回調(diào)來改變flutter頁面怪得，如：[[self reloadMessageChannel] sendMessage:@"full"];咱枉，具體看官方代碼
自己的理解：下面第一行代碼這種設(shè)置路由純屬多余卑硫，雖然路由值設(shè)置成功了（這里只能說是路由值，具體的路由頁面可不一定切換成功了）蚕断，因?yàn)橛玫氖侨?code>FlutterEngine獲取的FlutterViewController欢伏，此時(shí)是不加載flutter的main函數(shù)的。這種情況要想切換頁面必須通過channel進(jìn)行回調(diào)flutter端切換路由頁面的方法亿乳。所以我覺得下面的第一行代碼純屬多余硝拧，即使注釋掉也不影響。暫且把它當(dāng)作通過FlutterEngine設(shè)置路由值的一種方法吧风皿。

  [[self engine].navigationChannel invokeMethod:@"setInitialRoute"
                                      arguments:@"full"];
  [[self reloadMessageChannel] sendMessage:@"full"];

  FullScreenViewController *flutterViewController =
      [[FullScreenViewController alloc] initWithEngine:[self engine]
                                               nibName:nil
                                                bundle:nil];
  [self.navigationController
      pushViewController:flutterViewController
                animated:NO]; // Animating this is problematic.

??直接使用 FlutterViewController河爹，在連續(xù)返回然后進(jìn)入的操作下可能會閃退，建議在 FlutterViewController消失的情況下執(zhí)行以下代碼

-(void)viewWillDisappear:(BOOL)animated {
  [super viewWillDisappear:animated];
  if (self.isMovingFromParentViewController) {
    // Note that if we were doing things that might cause the VC
    // to disappear (like using the image_picker plugin)
    // we shouldn't do this.  But in this case we know we're
    // just going back to the navigation controller.
    // If we needed Flutter to tell us when we could actually go away,
    // we'd need to communicate over a method channel with it.
    [self.engine setViewController:nil];
  }
}

• 附加知識點(diǎn)

1. 常量構(gòu)造函數(shù)的作用桐款？
   理解：const修飾的構(gòu)造函數(shù)咸这，要求成員變量必須都是final的，并且在構(gòu)造函數(shù)中要初始化
   在類內(nèi)部修飾const如果修飾成員變量魔眨，必須和static配合使用

class Hello {
  const Hello(this.name,this.age);
  
  final String name;
  final int age;
}