平臺通訊的3中方式 Flutter 與 Native 端通訊有如下3個方法：
MethodChannel：Flutter 與 Native 端相互呼叫，呼叫後可以返回結果，可以 Native 端主動呼叫，也可以Flutter主動呼叫，屬於雙向通訊。此方式為最常用的方式， Native 端呼叫需要在主執行緒中執行。
BasicMessageChannel：用於使用指定的編解碼器對訊息進行編碼和解碼，屬於雙向通訊，可以 Native 端主動呼叫，也可以Flutter主動呼叫。
EventChannel：用於資料流（event streams）的通訊， Native 端主動傳送資料給 Flutter，通常用於狀態的監聽，比如網路變化、感測器資料等。
Flutter 與 Native 端通訊是非同步的。
通訊與平臺執行緒 Native 端主動傳送資料給 Flutter時，Native 端程式碼需要在主執行緒中執行，Android 端從子執行緒跳轉到主執行緒方式：
Kotlin 程式碼： Handler(Looper.getMainLooper()).post { }
Java 程式碼：
new Handler(Looper.getMainLooper()).post(new Runnable() {
@Override
public void run() {
}
});
複製程式碼 如果可以獲取到當前 Activity，也可以使用如下方式：
activity.runOnUiThread { }
iOS 端從子執行緒跳轉到主執行緒方式：
Objective-C 程式碼： dispatch_async(dispatch_get_main_queue(), ^{ });
Swift 程式碼： 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。
複製程式碼傳送訊息：
var result = await channel.invokeMethod('sendData',{'name': 'laomeng', 'age': 18})
複製程式碼第一個參數列示method，方法名稱，原生端會解析此引數。 第二個參數列示引數，型別任意，多個引數通常使用Map。 返回 Future，原生端返回的資料。
完整程式碼：
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('傳送資料到原生'),
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('原生返回資料：$_data')
],
),
);
}
}
複製程式碼Android 端 android 下建立 MethodChannelDemo：
package com.flutter.guide
import io.flutter.plugin.common.BinaryMessenger
import io.flutter.plugin.common.MethodCall
import io.flutter.plugin.common.MethodChannel
/**
* des:
*/
class MethodChannelDemo(messenger: BinaryMessenger): MethodChannel.MethodCallHandler {
private var channel: MethodChannel
init {
channel = MethodChannel(messenger, "com.flutter.guide.MethodChannel")
channel.setMethodCallHandler(this)
}
override fun onMethodCall(call: MethodCall, result: MethodChannel.Result) {
}
}
複製程式碼onMethodCall 方法在 Flutter 端呼叫 invokeMethod 方法回撥，
解析方法如下：
override fun onMethodCall(call: MethodCall, result: MethodChannel.Result) {
if (call.method == "sendData") {
val name = call.argument("name") as String?
val age = call.argument("age") as Int?
var map = mapOf("name" to "hello,$name",
"age" to "$age"
)
result.success(map)
}
}
複製程式碼call.method 字串就是 invokeMethod 方法傳入的 method。 call.argument 是 invokeMethod 傳入的引數，由於 Flutter 端傳入的是 Map，所以上面的解析按照 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 啟動：
class MainActivity : FlutterActivity() {
override fun configureFlutterEngine(flutterEngine: FlutterEngine) {
super.configureFlutterEngine(flutterEngine)
MethodChannelDemo(flutterEngine.dartExecutor.binaryMessenger)
}
}
複製程式碼iOS 端 ios 下建立 MethodChannelDemo，
按如下方式：
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])
}
}
}
}
}
複製程式碼在 AppDelegate 啟動：
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)
}
}
複製程式碼原生端主動傳送訊息給Flutter Flutter 端接收資料
@override
void initState() {
super.initState();
channel.setMethodCallHandler((call) {
setState(() {
_nativeData = call.arguments['count'];
});
});
}
複製程式碼Android 傳送資料 原生端啟動定時器，每隔一秒向 Flutter 傳送資料，Android 端程式碼：
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)
}
}
}
複製程式碼注意：Android 端傳送資料要在主現場中呼叫，即：
activity.runOnUiThread {
var map = mapOf("count" to count++)
channel.invokeMethod("timer", map)
}
啟動修改如下：
class MainActivity : FlutterActivity() {
override fun configureFlutterEngine(flutterEngine: FlutterEngine) {
super.configureFlutterEngine(flutterEngine)
MethodChannelDemo(this,flutterEngine.dartExecutor.binaryMessenger)
flutterEngine.plugins.add(MyPlugin())
}
}
複製程式碼iOS 傳送資料 iOS 端啟動定時器程式碼如下：
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)
}
}
複製程式碼