Flutter iOS methodchannel for http calls (workaround for internal MobileIron base apps) - https://github.com/flutter/flutter/issues/41500

AppDelegate.swift

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
    let httpChannel = FlutterMethodChannel(name: "com.example.flutter/http",
                                              binaryMessenger: controller.binaryMessenger)
    httpChannel.setMethodCallHandler({
        (call: FlutterMethodCall, result: @escaping FlutterResult) -> Void in
        // Note: this method is invoked on the UI thread.
        guard call.method == "http-get" || call.method == "http-post" else {
            result(FlutterMethodNotImplemented)
            return
        }
        
        if (call.method == "http-get") {
            let session = URLSession.shared
            let args = call.arguments as! NSDictionary
            let url = args["url"] as! String
            let clientId = args["client_id"] as! String
            let clientSecret = args["client_secret"] as! String

            var request = URLRequest(url: URL(string: url)!)
            request.setValue(clientId, forHTTPHeaderField: "client_id")
            request.setValue(clientSecret, forHTTPHeaderField: "client_secret")
            request.httpMethod = "GET"
            
            let task = session.dataTask(with: request) { data, response, error in
                result([
                    "data": String(data: data!, encoding: .utf8)!,
                    "statusCode": (response as? HTTPURLResponse)?.statusCode
                ]);
            }

            task.resume()
        }
        
        if (call.method == "http-post") {
            // Do any additional setup after loading the view.
            let session = URLSession.shared
            let args = call.arguments as! NSDictionary
            let url = args["url"] as! String
            let body = args["body"] as! String
            let clientId = args["client_id"] as! String
            let clientSecret = args["client_secret"] as! String

            var request = URLRequest(url: URL(string: url)!)
            request.setValue(clientId, forHTTPHeaderField: "client_id")
            request.setValue(clientSecret, forHTTPHeaderField: "client_secret")
            request.setValue("application/json", forHTTPHeaderField: "Content-Type")
            request.httpBody = body.data(using: .utf8)
            request.httpMethod = "POST"
            
            let task = session.dataTask(with: request) { data, response, error in
                result([
                    "data": String(data: data!, encoding: .utf8)!,
                    "statusCode": (response as? HTTPURLResponse)?.statusCode
                ]);
            }

            task.resume()
        }
    })
    
    GeneratedPluginRegistrant.register(with: self)
    return super.application(application, didFinishLaunchingWithOptions: launchOptions)
  }
}

http-service.dart

import 'package:dio/dio.dart';
import 'package:flutter/services.dart';

class MobileIronHttpChannel {
  static const platform = const MethodChannel('com.example.flutter/http');

  Future<Response> get(String clientId, String clientSecret, String url) async {
    Map data = await platform.invokeMethod('http-get', {
      "url": url,
      "client_id": clientId,
      "client_secret": clientSecret,
    });
    return Response(
      data: data["data"],
      statusCode: data["statusCode"],
    );
  }

  Future<Response> post(String clientId, String clientSecret, String url, String jsonBody) async {
    Map data = await platform.invokeMethod('http-post', {
      "url": url,
      "client_id": clientId,
      "client_secret": clientSecret,
      "body": jsonBody,
    });
    return Response(
      data: data["data"],
      statusCode: data["statusCode"],
    );
  }
}