【Flutter 混合開發】與原生通訊-MethodChannel
Flutter 混合開發系列 包含如下：
- 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
每個工作日分享一篇，歡迎關注、點贊及轉發。
平台通訊的3中方式
Flutter 與 Native 端通訊有如下3個方法：
- MethodChannel：Flutter 與 Native 端相互調用，調用後可以返回結果，可以 Native 端主動調用，也可以Flutter主動調用，屬於雙向通訊。此方式為最常用的方式， Native 端調用需要在主執行緒中執行。
- 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，可以 Native 端主動調用，也可以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，通常用於狀態的監聽，比如網路變化、感測器數據等。
通訊架構圖
此圖為官方的架構圖
Flutter 與 Native 端通訊是非同步的。
通訊與平台執行緒
Native 端主動發送數據給 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() {
}
});
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 端創建 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，多個參數通常使用Map。
- 返回 Future，原生端返回的數據。
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('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：$_data')
],
),
);
}
}
Android 端
android 下創建 MethodChannelDemo：
package com.flutter.guide
import io.flutter.plugin.common.BinaryMessenger
import io.flutter.plugin.common.MethodCall
import io.flutter.plugin.common.MethodChannel
/**
* des:
*/
class MethodChannelDemo(messenger: BinaryMessenger): MethodChannel.MethodCallHandler {
private var channel: MethodChannel
init {
channel = MethodChannel(messenger, "com.flutter.guide.MethodChannel")
channel.setMethodCallHandler(this)
}
override fun onMethodCall(call: MethodCall, result: MethodChannel.Result) {
}
}
onMethodCall 方法在 Flutter 端調用 invokeMethod 方法回調，解析方法如下：
override fun onMethodCall(call: MethodCall, result: MethodChannel.Result) {
if (call.method == "sendData") {
val name = call.argument("name") as String?
val age = call.argument("age") as Int?
var map = mapOf("name" to "hello,$name",
"age" to "$age"
)
result.success(map)
}
}
- call.method 字元串就是 invokeMethod 方法傳入的 method。
- call.argument 是 invokeMethod 傳入的參數，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)
}
}
iOS 端
ios 下創建 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])
}
}
}
}
}
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)
}
}
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
原生端啟動定時器，每隔一秒向 Flutter 發送數據，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)
}
}
}
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) }
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())
}
}
iOS 發送數據
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)
}
}
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