如何在Flutter后台通过Method Channel调用API并控制Android/iOS端Onesignal通知

下面分步骤实现需求，涵盖Flutter侧、Android原生和iOS原生的代码示例：

一、Flutter侧：后台Method Channel与API调用实现 #

1. 定义Method Channel并注册回调 #

在Flutter中创建专属Method Channel，用于和原生端后台交互，并实现API调用逻辑：

import 'dart:convert';
import 'package:http/http.dart' as http;
import 'package:flutter/services.dart';

// 定义Method Channel名称，需和原生端保持一致
const MethodChannel _backgroundChannel = MethodChannel('com.your.app/notification_check');

// 后台API调用逻辑，返回是否允许显示通知的布尔值
Future<bool> _checkNotificationPermission() async {
  try {
    // 调用目标API替换为你的实际接口地址
    final response = await http.get(Uri.parse('https://your-api-domain.com/api/allow-notification'));
    
    if (response.statusCode == 200) {
      final responseData = jsonDecode(response.body);
      // 根据API返回字段判断是否允许显示通知
      return responseData['allow_show'] ?? false;
    }
    // API请求失败默认返回不允许
    return false;
  } catch (e) {
    // 捕获网络异常或解析错误，默认不允许显示通知
    return false;
  }
}

// 注册Method Channel回调，建议在main函数初始化时调用
void setupBackgroundChannelHandler() {
  _backgroundChannel.setMethodCallHandler((call) async {
    if (call.method == 'requestNotificationPermission') {
      return await _checkNotificationPermission();
    }
    throw MissingPluginException('Method not implemented');
  });
}

二、Android原生端：根据API响应控制OneSignal通知 #

1. 配置OneSignal后台回调与Method Channel交互 #

在Android的Application类中初始化OneSignal，并在通知接收回调中调用Flutter的Method Channel获取结果，决定是否显示通知：

import android.app.Application
import com.onesignal.OSNotificationReceivedEvent
import com.onesignal.OneSignal
import io.flutter.embedding.engine.FlutterEngine
import io.flutter.embedding.engine.dart.DartExecutor
import io.flutter.plugin.common.MethodChannel

class App : Application(), OneSignal.OSNotificationReceivedHandler {
    private lateinit var backgroundChannel: MethodChannel

    override fun onCreate() {
        super.onCreate()
        
        // 初始化OneSignal，替换为你的App ID
        OneSignal.initWithContext(this)
        OneSignal.setAppId("YOUR_ONESIGNAL_APP_ID")
        OneSignal.setNotificationReceivedHandler(this)
        
        // 初始化Flutter Engine用于后台Method Channel调用
        val flutterEngine = FlutterEngine(this)
        flutterEngine.dartExecutor.executeDartEntrypoint(
            DartExecutor.DartEntrypoint.createDefault()
        )
        backgroundChannel = MethodChannel(flutterEngine.dartExecutor.binaryMessenger, "com.your.app/notification_check")
    }

    override fun notificationReceived(event: OSNotificationReceivedEvent) {
        // 异步调用Flutter侧的权限检查方法
        backgroundChannel.invokeMethod("requestNotificationPermission", null, object : MethodChannel.Result {
            override fun success(result: Any?) {
                val shouldShow = result as Boolean
                if (shouldShow) {
                    // 允许显示通知，将原事件传递完成
                    event.complete(event.notification)
                } else {
                    // 拒绝显示通知，传递null取消通知
                    event.complete(null)
                }
            }

            override fun error(errorCode: String, errorMessage: String?, errorDetails: Any?) {
                // 调用失败默认取消通知
                event.complete(null)
            }

            override fun notImplemented() {
                event.complete(null)
            }
        })
    }
}

2. 必要权限配置 #

在AndroidManifest.xml中添加后台运行和网络权限：

<uses-permission android:name="android.permission.INTERNET" />
<uses-permission android:name="android.permission.FOREGROUND_SERVICE" />
<uses-permission android:name="android.permission.ACCESS_NETWORK_STATE" />

三、iOS原生端：根据API响应控制OneSignal通知 #

1. 配置OneSignal回调与Method Channel交互 #

在AppDelegate中初始化OneSignal，并实现通知接收回调，调用Flutter侧的方法获取结果：

import UIKit
import Flutter
import OneSignal

@UIApplicationMain
class AppDelegate: FlutterAppDelegate, OSNotificationReceivedDelegate {
    private var backgroundChannel: FlutterMethodChannel!

    override func application(
        _ application: UIApplication,
        didFinishLaunchingWithOptions launchOptions: [UIApplication.LaunchOptionsKey: Any]?
    ) -> Bool {
        // 初始化OneSignal，替换为你的App ID
        OneSignal.setAppId("YOUR_ONESIGNAL_APP_ID")
        OneSignal.setNotificationReceivedDelegate(self)
        
        let controller = window?.rootViewController as! FlutterViewController
        backgroundChannel = FlutterMethodChannel(name: "com.your.app/notification_check", binaryMessenger: controller.binaryMessenger)
        
        GeneratedPluginRegistrant.register(with: self)
        return super.application(application, didFinishLaunchingWithOptions: launchOptions)
    }

    func notificationReceived(_ notificationReceivedEvent: OSNotificationReceivedEvent) {
        // 调用Flutter侧的权限检查方法
        backgroundChannel.invokeMethod("requestNotificationPermission", arguments: nil) { result in
            guard let shouldShow = result as? Bool else {
                // 结果异常默认取消通知
                notificationReceivedEvent.complete(nil)
                return
            }
            
            if shouldShow {
                // 允许显示通知
                notificationReceivedEvent.complete(notificationReceivedEvent.notification)
            } else {
                // 取消通知
                notificationReceivedEvent.complete(nil)
            }
        }
    }
}

2. 后台模式配置 #

在Info.plist中添加远程通知后台权限：

<key>UIBackgroundModes</key>
<array>
    <string>remote-notification</string>
</array>

四、关键注意事项 #

• API调用稳定性：Flutter后台环境下网络调用可能受系统限制，需设置合理超时时间，避免阻塞原生通知处理流程。
• OneSignal通知参数：发送静默通知时，Android需携带data字段，iOS需设置content-available: 1，才能触发后台回调。
• Flutter Engine复用：Android端建议复用Flutter Engine，避免重复初始化带来的性能损耗；iOS端需确保FlutterViewController在后台能正常响应Method Channel调用。

内容的提问来源于stack exchange，提问作者jos Sea