【Flutter 混合開發】與原生通訊-MethodChannel

時間 2020-10-25

標籤 java android ios git swift api 微信網絡架構 app 欄目 Java 简体版

原文原文鏈接

Flutter 混合開發系列包含以下：java

嵌入原生View-Android

嵌入原生View-iOS

與原生通訊-MethodChannel

與原生通訊-BasicMessageChannel

與原生通訊-EventChannel

添加 Flutter 到 Android Activity

添加 Flutter 到 Android Fragment

添加 Flutter 到 iOS

每一個工做日分享一篇，歡迎關注、點贊及轉發。android

平臺通訊的3中方式

Flutter 與 Native 端通訊有以下3個方法：ios

MethodChannel：Flutter 與 Native 端相互調用，調用後能夠返回結果，能夠 Native 端主動調用，也能夠Flutter主動調用，屬於雙向通訊。此方式爲最經常使用的方式， Native 端調用須要在主線程中執行。
BasicMessageChannel：用於使用指定的編解碼器對消息進行編碼和解碼，屬於雙向通訊，能夠 Native 端主動調用，也能夠Flutter主動調用。
EventChannel：用於數據流（event streams）的通訊， Native 端主動發送數據給 Flutter，一般用於狀態的監聽，好比網絡變化、傳感器數據等。

通訊架構圖

此圖爲官方的架構圖git

Flutter 與 Native 端通訊是異步的。swift

通訊與平臺線程

Native 端主動發送數據給 Flutter時，Native 端代碼須要在主線程中執行，Android 端從子線程跳轉到主線程方式：api

Kotlin 代碼：微信

Handler(Looper.getMainLooper()).post {
  
}

Java 代碼：網絡

new Handler(Looper.getMainLooper()).post(new Runnable() {
  @Override
  public void run() {
    
  }
});

若是能夠獲取到當前 Activity，也能夠使用以下方式：架構

activity.runOnUiThread {
   
}

iOS 端從子線程跳轉到主線程方式：app

Objective-C 代碼：

dispatch_async(dispatch_get_main_queue(), ^{
  
});

Swift 代碼：

DispatchQueue.main.async {
  
}

MethodChannel

Flutter 端

Flutter 端建立 MethodChannel 通道，用於與原生端通訊：

var channel = MethodChannel('com.flutter.guide.MethodChannel');

com.flutter.guide.MethodChannel 是 MethodChannel 的名稱，原生端要與之對應。

發送消息：

var result = await channel.invokeMethod('sendData',{'name': 'laomeng', 'age': 18})

第一個參數表示method，方法名稱，原生端會解析此參數。
第二個參數表示參數，類型任意，多個參數一般使用Map。
返回 Future，原生端返回的數據。

完整代碼：

class MethodChannelDemo extends StatefulWidget {
  @override
  _MethodChannelDemoState createState() => _MethodChannelDemoState();
}

class _MethodChannelDemoState extends State<MethodChannelDemo> {
  var channel = MethodChannel('com.flutter.guide.MethodChannel');

  var _data;

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(),
      body: Column(
        children: [
          SizedBox(
            height: 50,
          ),
          RaisedButton(
            child: Text('發送數據到原生'),
            onPressed: () async {
              var result = await channel
                  .invokeMethod('sendData', {'name': 'laomeng', 'age': 18});
              var name = result['name'];
              var age = result['age'];
              setState(() {
                _data = '$name,$age';
              });
            },
          ),
          Text('原生返回數據：$_data')
        ],
      ),
    );
  }
}

Android 端

android 下建立 MethodChannelDemo：

package com.flutter.guide

import io.flutter.plugin.common.BinaryMessenger
import io.flutter.plugin.common.MethodCall
import io.flutter.plugin.common.MethodChannel

/**
 * des:
 */
class MethodChannelDemo(messenger: BinaryMessenger): MethodChannel.MethodCallHandler {

    private var channel: MethodChannel

    init {
        channel = MethodChannel(messenger, "com.flutter.guide.MethodChannel")
        channel.setMethodCallHandler(this)
    }

    override fun onMethodCall(call: MethodCall, result: MethodChannel.Result) {
        
    }
}

onMethodCall 方法在 Flutter 端調用 invokeMethod 方法回調，解析方法以下：

override fun onMethodCall(call: MethodCall, result: MethodChannel.Result) {
    if (call.method == "sendData") {
        val name = call.argument("name") as String?
        val age = call.argument("age") as Int?

        var map = mapOf("name" to "hello,$name",
                "age" to "$age"
        )
        result.success(map)
    }
}

call.method 字符串就是 invokeMethod 方法傳入的 method。
call.argument 是 invokeMethod 傳入的參數，因爲 Flutter 端傳入的是 Map，因此上面的解析按照 Map 解析。
result.success() 是返回給 Flutter 的結果。

Flutter 端解析：

var result = await channel
    .invokeMethod('sendData', {'name': 'laomeng', 'age': 18});
var name = result['name'];
var age = result['age'];

兩端的解析要相互對應。

在 MainActivity 啓動：

class MainActivity : FlutterActivity() {
    
    override fun configureFlutterEngine(flutterEngine: FlutterEngine) {
        super.configureFlutterEngine(flutterEngine)
        MethodChannelDemo(flutterEngine.dartExecutor.binaryMessenger)
    }
}

iOS 端

ios 下建立 MethodChannelDemo，按以下方式：

import Flutter
import UIKit

public class MethodChannelDemo {
    
    init(messenger: FlutterBinaryMessenger) {
        let channel = FlutterMethodChannel(name: "com.flutter.guide.MethodChannel", binaryMessenger: messenger)
        channel.setMethodCallHandler { (call:FlutterMethodCall, result:@escaping FlutterResult) in
            if (call.method == "sendData") {
                if let dict = call.arguments as? Dictionary<String, Any> {
                    let name:String = dict["name"] as? String ?? ""
                    let age:Int = dict["age"] as? Int ?? -1
                    result(["name":"hello,\(name)","age":age])
                }
            }
        }
    }
}

在 AppDelegate 啓動：

import UIKit
import Flutter

@UIApplicationMain
@objc class AppDelegate: FlutterAppDelegate {
  override func application(
    _ application: UIApplication,
    didFinishLaunchingWithOptions launchOptions: [UIApplication.LaunchOptionsKey: Any]?
  ) -> Bool {
    
    let controller : FlutterViewController = window?.rootViewController as! FlutterViewController
    MethodChannelDemo(messenger: controller.binaryMessenger)
    GeneratedPluginRegistrant.register(with: self)
    
    return super.application(application, didFinishLaunchingWithOptions: launchOptions)
  }
}

原生端主動發送消息給Flutter

Flutter 端接收數據

@override
void initState() {
  super.initState();
  channel.setMethodCallHandler((call) {
    setState(() {
      _nativeData = call.arguments['count'];
    });
  });
}

Android 發送數據

原生端啓動定時器，每隔一秒向 Flutter 發送數據，Android 端代碼：

class MethodChannelDemo(var activity: Activity, messenger: BinaryMessenger) : MethodChannel.MethodCallHandler {

    private var channel: MethodChannel
    private var count = 0

    init {
        channel = MethodChannel(messenger, "com.flutter.guide.MethodChannel")
        channel.setMethodCallHandler(this)
        startTimer()
    }


    fun startTimer() {
        var timer = Timer().schedule(timerTask {
            activity.runOnUiThread {
                var map = mapOf("count" to count++)
                channel.invokeMethod("timer", map)
            }
        }, 0, 1000)

    }

    override fun onMethodCall(call: MethodCall, result: MethodChannel.Result) {
        if (call.method == "sendData") {
            val name = call.argument("name") as String?
            val age = call.argument("age") as Int?

            var map = mapOf("name" to "hello,$name",
                    "age" to "$age"
            )
            result.success(map)
        }
    }
}

注意：Android 端發送數據要在主現場中調用，即：
activity.runOnUiThread {
             var map = mapOf("count" to count++)
             channel.invokeMethod("timer", map)
         }

啓動修改以下：

class MainActivity : FlutterActivity() {

    override fun configureFlutterEngine(flutterEngine: FlutterEngine) {
        super.configureFlutterEngine(flutterEngine)
        MethodChannelDemo(this,flutterEngine.dartExecutor.binaryMessenger)
        flutterEngine.plugins.add(MyPlugin())
    }
}

iOS 發送數據

iOS 端啓動定時器代碼以下：

import Flutter
import UIKit

public class MethodChannelDemo {
    var count =  0
    var channel:FlutterMethodChannel
    init(messenger: FlutterBinaryMessenger) {
        channel = FlutterMethodChannel(name: "com.flutter.guide.MethodChannel", binaryMessenger: messenger)
        channel.setMethodCallHandler { (call:FlutterMethodCall, result:@escaping FlutterResult) in
            if (call.method == "sendData") {
                if let dict = call.arguments as? Dictionary<String, Any> {
                    let name:String = dict["name"] as? String ?? ""
                    let age:Int = dict["age"] as? Int ?? -1
                    result(["name":"hello,\(name)","age":age])
                }
            }
        }
        startTimer()
    }
    
    func startTimer() {
        var timer = Timer.scheduledTimer(timeInterval:1, target: self, selector:#selector(self.tickDown),userInfo:nil,repeats: true)
    }
    @objc func tickDown(){
        count += 1
        var args = ["count":count]
        channel.invokeMethod("timer", arguments:args)
    }
}