场景
- Flutter项目中需要与Native进行通信
- Android原生项目嵌入Flutter开发模块
- iOS原生项目嵌入Flutter开发模块
- Flutter插件开发
image
平台通道数据类型支持
| Dart | Android | iOS |
|---|---|---|
| null | null | nil (NSNull when nested) |
| bool | java.lang.Boolean | NSNumber numberWithBool: |
| int | java.lang.Integer | NSNumber numberWithInt: |
| int, 如果不足32位 | java.lang.Long | NSNumber numberWithLong: |
| int, 如果不足64位 | java.math.BigInteger | FlutterStandardBigInteger |
| double | java.lang.Double | NSNumber numberWithDouble: |
| String | java.lang.String | NSString |
| Uint8List | byte[] | FlutterStandardTypedData typedDataWithBytes: |
| Int32List | int[] | FlutterStandardTypedData typedDataWithInt32: |
| Int64List | long[] | FlutterStandardTypedData typedDataWithInt64: |
| Float64List | double[] | FlutterStandardTypedData typedDataWithFloat64: |
| List | java.util.ArrayList | NSArray |
| Map | java.util.HashMap | NSDictionary |
当在发送和接收值时，这些值在消息中的序列化和反序列化会自动进行。
平台通道
Platform Channel 是所以 Flutter 提供的和平台端通信的工具，针对不同的使用场景，Platform Channel 又分为以下三类：
- Message channel：用于传递字符串和半结构化的信息,支持使用自定义消息编解码器进行基本的异步消息传递
- Method channel：用于传递方法调用（method invocation）
- Event channel：用于数据流（event streams）的通信,通常用在需要进行实时监听的使用场景，比如：网络状态，电池充电状态以及一些监听器的实现
Flutter项目中需要与Native进行通信-实战
我们这里仅使用Method channel和Event channel进行通信实战
要实现的功能：
- Flutter给Native传递三个参数，Native要把这三个参数相加得到的结果返回给Flutter，并显示在Flutter界面上
- Native写一个定时器，每隔1秒进行“+1操作”，每次“+1”后，把结果传递给Flutter，当结果大于30的时候结束定时器
功能1：
Android端：
创建MethodChannelDemo.kt
class MethodChannelDemo (messenger: BinaryMessenger): MethodChannel.MethodCallHandler{
private var channel: MethodChannel = MethodChannel(messenger, "com.mufeng.flutterNativeChannel.MethodChannel")
init {
channel.setMethodCallHandler(this)
}
override fun onMethodCall(call: MethodCall, result: MethodChannel.Result) {
when(call.method){
"add" -> {
val params1 = call.argument("params1")
val params2 = call.argument("params2")
val params3 = call.argument("params3")
val params = params1!! + params2!! + params3!!
result.success(params)
}
}
}
}
在MainActivity中启动平台通道
class MainActivity: FlutterActivity() {
override fun configureFlutterEngine(flutterEngine: FlutterEngine) {
super.configureFlutterEngine(flutterEngine)
MethodChannelDemo(flutterEngine.dartExecutor.binaryMessenger)
}
}
iOS端
创建MethodChannelDemo.swift
//
// MethodChannelDemo.swift
// Runner
//
// Created by a on 2020/12/28.
//
import Foundation
import Flutter
import UIKit
public class MethodChannelDemo {
init(messenger: FlutterBinaryMessenger) {
let channel = FlutterMethodChannel(name: "com.mufeng.flutterNativeChannel.MethodChannel", binaryMessenger: messenger)
channel.setMethodCallHandler{ (call: FlutterMethodCall, result:@escaping FlutterResult)in
if(call.method == "add"){
if let dict = call.arguments as? Dictionary{
let params1: Int = dict["params1"] as? Int ?? 0
let params2: Int = dict["params2"] as? Int ?? 0
let params3: Int = dict["params3"] as? Int ?? 0
result(params1 + params2 + params3)
}
}
}
}
}
在 AppDelegate 中启动平台通道：
import UIKit
import Flutter
@UIApplicationMain
@objc class AppDelegate: FlutterAppDelegate {
override func application(
_ application: UIApplication,
didFinishLaunchingWithOptions launchOptions: [UIApplication.LaunchOptionsKey: Any]?
) -> Bool {
/// start
let controller: FlutterViewController = window?.rootViewController as! FlutterViewController
MethodChannelDemo(messenger: controller.binaryMessenger)
/// end
GeneratedPluginRegistrant.register(with: self)
return super.application(application, didFinishLaunchingWithOptions: launchOptions)
}
}
在ios中也用同样的操作，要保证平台通道的channel保持一致，这样在Flutter中就可以保证一套代码试用两个平台了
Flutter
/// 保证平台channel保持一致
var channel = MethodChannel('com.mufeng.flutterNativeChannel.MethodChannel');
var result = await channel.invokeMethod('add', {'params1': int.parse(controller1.text), 'params2': int.parse(controller2.text), 'params3': int.parse(controller3.text)});
setState(() {
this.result = result.toString();
});
显示结果：
Android：
image
iOS:
image
功能2：
Android端
android 下创建 EventChannelDemo：
package com.mufeng.flutter_native_channel
import android.app.Activity
import io.flutter.plugin.common.BinaryMessenger
import io.flutter.plugin.common.EventChannel
import java.util.*
import kotlin.concurrent.timerTask
class EventChannelDemo(private var activity: Activity, messenger: BinaryMessenger) : EventChannel.StreamHandler {
private var channel: EventChannel = EventChannel(messenger, "com.mufeng.flutterNativeChannel.EventChannel")
private var count = 0
private var events: EventChannel.EventSink? = null
init {
channel.setStreamHandler(this)
startTimer()
}
private fun startTimer() {
var timer = Timer().schedule(timerTask {
count++
val map = mapOf("count" to count)
activity.runOnUiThread {
// 必须运行在主线程
events?.success(map)
}
if(count >= 30){
activity.runOnUiThread {
events?.error("400", "超过30秒,倒计时结束", null)
}
cancel()
}
}, 0, 1000)
}
override fun onListen(arguments: Any?, events: EventChannel.EventSink?) {
this.events = events
}
override fun onCancel(arguments: Any?) {
this.events = null
}
}
在 MainActivity 启动：
class MainActivity: FlutterActivity() {
override fun configureFlutterEngine(flutterEngine: FlutterEngine) {
super.configureFlutterEngine(flutterEngine)
// MethodChannelDemo(flutterEngine.dartExecutor.binaryMessenger)
EventChannelDemo(this, flutterEngine.dartExecutor.binaryMessenger)
}
}
iOS端
ios 下创建 EventChannelDemo
import Foundation
import Flutter
import UIKit
public class EventChannelDemo: NSObject, FlutterStreamHandler {
var channel: FlutterEventChannel?
var count = 0
var events: FlutterEventSink?
var timer: Timer?
public override init() {
super.init()
}
convenience init(messenger: FlutterBinaryMessenger) {
self.init()
channel = FlutterEventChannel(name: "com.mufeng.flutterNativeChannel.EventChannel", binaryMessenger: messenger)
channel?.setStreamHandler(self)
startTimer()
}
func startTimer() {
timer = Timer.scheduledTimer(timeInterval: 1, target: self,selector: #selector(self.tickDown),userInfo: nil,repeats: true)
}
@objc func tickDown(){
count += 1
let args = ["count": count]
if(events != nil){
events!(args)
}
if(count >= 30){
if(events != nil){
events!(FlutterError.init(code: "400", message: "超过30秒,倒计时结束", details: nil))
}
timer?.fireDate = Date.distantFuture
timer?.invalidate()
}
}
public func onListen(withArguments arguments: Any?, eventSink events: @escaping FlutterEventSink) -> FlutterError? {
self.events = events
return nil
}
public func onCancel(withArguments arguments: Any?) -> FlutterError? {
self.events = nil
timer?.invalidate()
self.timer = nil
return nil
}
}
在 AppDelegate 启动：
@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)
EventChannelDemo(messenger: controller.binaryMessenger)
GeneratedPluginRegistrant.register(with: self)
return super.application(application, didFinishLaunchingWithOptions: launchOptions)
}
}
Flutter端
var _eventChannel = EventChannel('com.mufeng.flutterNativeChannel.EventChannel');
_eventChannel.receiveBroadcastStream().listen(_listen, onError: (value){
print(value);
});
void _listen(event) {
setState(() {
second = event['count'].toString();
});
}
显示结果
Android：
// 打印出原生发挥的错误信息
I/flutter (24053): PlatformException(400, 超过30秒,倒计时结束, null, null)
image
iOS：
// 打印出原生发挥的错误信息
flutter: PlatformException(400, 超过30秒,倒计时结束, null, null)
image
源码地址：flutter_native_channel
总结
Flutter 与 Native 通信在 Flutter 应用中几乎是不可缺少的步骤，所以掌握其原理和实际用法尤其重要。熟练的掌握Flutter与Native的通信能极大的提高开发效率
感谢
老孟Flutter
Flutter中文网-Flutter实战