Flutter开发进阶：Channel 1.初始化路由传值 2.MethodChannel通信 3.Channel 4.Flutter引擎源码

1.初始化路由传值

//ios
let vc = FlutterViewController()
vc.setInitialRoute("openCompany")//设置为one
self.navigatonController?.present(vc, animated:true)

//flutter
void main() => runApp(MyApp(pageIndex:window.defaultRouteName));

class MyApp extends StatelessWidget {
  final String pageIndex;//接收到openCompany
  const MyApp({Key? key, required this.pageIndex}) : super(key:key);
  
  Widget build(BuildContext context){
    //根据pageIndex去加载页面
    return ...
  }
}

• 是单向的，只能App给flutter传递，导致页面不能关闭。

2.MethodChannel通信

//ios
let engine = FlutterEngine(name: "app")
var flutter : FlutterViewController? = nil

override func viewDidLoad(){
  engine.run()
  
  self.flutter = FlutterViewController(engine: self.engine, nibName: nil, bundle: nil)
}

override func touchesEnded(_ touches: Set<UITouch>, with event: UIEvent?) {
  if let __flutter = self.flutter {
    let channel = FlutterMethodChannel(name: "explorer", binaryMessenger: __flutter.binaryMessenger)
    self.present(__flutter, animated: true, completion: nil)

    channel.setMethodCallHandler { method, result in
       if(method.method == "exit"){
           NX.print(method.method)
       }
    }
    channel.invokeMethod("openCompany", arguments:nil);
  }
}

//flutter
void main() => runApp(MyApp());

class MyApp extends StatefullWidget {
  const MyApp({Key? key});
  MyAppState createState() => MyAppState()
}

class MyAppState extends State<MyApp> {
  const channel = MethodChannel("explorer");
  String pageIndex;//接收到openCompany
  
  void initState(){
    channel.setMethodCallHandler((call){
      pageIndex = call.method;//openCompany
      setState({});
    });
  }
  
  Widget build(BuildContext context){
    //根据pageIndex去加载页面
    
    //响应事件
    {
       channel.invokeMapMethod("exit", {});
    }
    
    return ...
  }
}

• FlutterEngine模式下setInitialRoute失效

3.Channel

1.FlutterMethodChannel

传递方法的，方法调用（案例如上）

2.FlutterBasicMessageChannel

持续通信，收到消息后还可以恢复

//ios
let channel = FlutterBasicMessageChannel(name: "explorer", binaryMessenger: __flutter.binaryMessenger)
channel.setMessageHandler { value, reply in
  //收到来自flutter的消息
}
channel.sendMessage("----")//发送给flutter的消息



//flutter
BasicMessageChannel channel = BasicMessageChannel("explor", StandardmessageCodec());
channel.setMessageHandler((message){
      //来自App的消息
}); 
channel.send("-----")//发给App的消息

3.EventChannel

数据流

4.Flutter引擎源码

https://blog.csdn.net/dongzhong1990/article/details/105678124

源码主要分为两部分：

Flutter官方源码下载路径：

engine: https://github.com/flutter/engine

flutter framework: https://github.com/flutter/flutter

• Engine，是可供Flutter宿主应用提供的一个可移植运行时。Engine实现了Flutter的核心库，包括动画、图形、文件、网络I/O、访问支持、插件架构和Dart的运行时、编译工具链；
• Flutter Framework，大部分的Flutter开发者主要通过Flutter Framework交互。Framework提供了一个现代的、可交互的框架，以及一个丰富的平台、布局、基础部件的集合。

1.channel通信原理

1.1.MethodChannel通信

let channel = FlutterMethodChannel(name:"explorer", binaryMessenger: self.flutterViewController.binaryMessenger)

初始化方法：将如下三个信息保存起来

• name：channel名称
• binaryMessenger:消息管理器
• codec:解码器(上层传空时下层会自动调用单例)

channel.setMethodCallHandler { method, result in
  if(method.method == "exit"){                
  }
}

设置消息回调：判断handler是否为空，来进行历史数据的清空和重新赋值。

• handler：最终毁掉到上层的一个句柄
• 内部会自己定义一个messageHandler，用来接收最下层的回调，并且可以把消息抛到最上层。
• 内部会将新定义的channel.name和messageHandler用key-value的形式保存起来。

channel.invokeMethod("openDetail", arguments: nil, result: {})

• 通过channel.name找到dart部分的消息回调，然后执行handler big你就爱哪个数据传递过去

2.解码器

三种channel有2种解码器，解码器实际上是一种数据转换协议，iOS、Android、dart三端通用。

2.1.FlutterMessageCodec

@protocol FlutterMessageCodec
+ (instancetype)sharedInstance;
- (NSData * _Nullable)encode:(id _Nullable)message;
- (id _Nullable)decode:(NSData * _Nullable)message;
@end

2.2FlutterMethodCodec

服务Methodchannel、EventChannel

@protocol FlutterMethodCodec
+ (instancetype)sharedInstance;
- (NSData *)encodeMethodCall:(FlutterMethodCall *)methodCall;
- (NSData *)decodeMethodCall:(NSData *)methodCall;
- (NSData *)encodeSuccessEnvelope:(id _Nullable)result;
- (NSData *)encodeErrorEnvelope:(FlutterError *)error;
- (id _Nullanle)decodeEnvelope:(NSData *)envelope;
@end

2.3 FlutterStandardReaderWriter

• FlutterStandardReader

- (nullable id)readValue {
  //
  [self readValueOfType:[self readByte]]
}

- (nullable id)readValueOfType:(UInt8)type{
  
}

• FlutterStandardWriter

- (void)writeValue:(id)value {
  //判断类型
  //写入标志位(数据类型)+数据本身
  [- writeByte:]
  [- writeBytes:- length:-]
}