Flutter Web获取本地IP

基础概念

Flutter Web 是 Flutter 框架的一个分支，它允许开发者使用 Flutter 构建跨平台的 Web 应用程序。Flutter Web 通过将 Flutter 的渲染引擎（基于 Skia 图形库）编译成 WebAssembly（Wasm），并在浏览器的 JavaScript 引擎中运行来实现这一点。

获取本地 IP 地址通常是指获取运行应用程序的计算机的本地网络接口的 IP 地址。这对于网络通信、多设备通信等场景非常有用。

类型

获取本地 IP 地址的方法有多种，常见的包括：

使用 JavaScript 获取：通过浏览器的 JavaScript API 获取本地 IP 地址。
使用原生代码获取：通过 Flutter 的平台通道（Platform Channels）调用原生代码获取本地 IP 地址。

应用场景

获取本地 IP 地址的应用场景包括：

局域网通信：在局域网内进行设备间的通信，如文件共享、游戏对战等。
P2P 网络：构建点对点网络应用，如视频会议、文件传输等。
本地服务器：启动本地服务器，供其他设备访问。

获取本地 IP 地址的方法

使用 JavaScript 获取本地 IP 地址

可以通过浏览器的 RTCPeerConnection API 获取本地 IP 地址。以下是一个示例代码：

import 'dart:async';
import 'package:flutter/material.dart';

void main() {
  runApp(MyApp());
}

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      home: Scaffold(
        appBar: AppBar(
          title: Text('Get Local IP'),
        ),
        body: Center(
          child: ElevatedButton(
            onPressed: () async {
              String localIP = await getLocalIP();
              print('Local IP: $localIP');
            },
            child: Text('Get Local IP'),
          ),
        ),
      ),
    );
  }

  Future<String> getLocalIP() async {
    final Completer<String> completer = Completer<String>();
    Timer.run(() {
      final RTCPeerConnection pc = RTCPeerConnection(
        iceServers: [],
      );
      pc.createDataChannel('');
      pc.createOffer().then((desc) {
        pc.setLocalDescription(desc);
      });
      pc.onicecandidate = (event) {
        if (event.candidate == null) {
          final addresses = pc.localDescription.sdp.matchAll(
            r'c=IN IP4 (\d+\.\d+\.\d+\.\d+)',
          );
          addresses.forEach((match) {
            completer.complete(match.group(1));
          });
        }
      };
    });
    return completer.future;
  }
}

使用原生代码获取本地 IP 地址

可以通过 Flutter 的平台通道调用原生代码获取本地 IP 地址。以下是一个示例代码：

Dart 代码：

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

void main() {
  runApp(MyApp());
}

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      home: Scaffold(
        appBar: AppBar(
          title: Text('Get Local IP'),
        ),
        body: Center(
          child: ElevatedButton(
            onPressed: () async {
              String localIP = await getLocalIP();
              print('Local IP: $localIP');
            },
            child: Text('Get Local IP'),
          ),
        ),
      ),
    );
  }

  Future<String> getLocalIP() async {
    const platform = MethodChannel('com.example/local_ip');
    try {
      final String ip = await platform.invokeMethod('getLocalIP');
      return ip;
    } on PlatformException catch (e) {
      print("Failed to get local IP: ${e.message}");
      return null;
    }
  }
}

原生代码（Android）：

在 MainActivity.java 中添加以下代码：

import android.content.Context;
import android.net.ConnectivityManager;
import android.net.NetworkInfo;
import android.net.NetworkCapabilities;
import android.os.Build;
import io.flutter.embedding.android.FlutterActivity;
import io.flutter.plugin.common.MethodChannel;

public class MainActivity extends FlutterActivity {
    private static final String CHANNEL = "com.example/local_ip";

    @Override
    public void configureFlutterEngine(FlutterEngine flutterEngine) {
        super.configureFlutterEngine(flutterEngine);
        new MethodChannel(flutterEngine.getDartExecutor().getBinaryMessenger(), CHANNEL)
            .setMethodCallHandler((call, result) -> {
                if (call.method.equals("getLocalIP")) {
                    result.success(getLocalIPAddress(this));
                } else {
                    result.notImplemented();
                }
            });
    }

    private String getLocalIPAddress(Context context) {
        try {
            final ConnectivityManager connectivityManager = (ConnectivityManager) context.getSystemService(Context.CONNECTIVITY_SERVICE);
            final NetworkInfo activeNetworkInfo = connectivityManager.getActiveNetworkInfo();
            if (activeNetworkInfo != null && activeNetworkInfo.isConnected()) {
                if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M) {
                    final NetworkCapabilities networkCapabilities = connectivityManager.getNetworkCapabilities(activeNetworkInfo.getConnection());
                    if (networkCapabilities != null && networkCapabilities.hasTransport(NetworkCapabilities.TRANSPORT_WIFI)) {
                        return getWifiIPAddress(context);
                    } else if (networkCapabilities != null && networkCapabilities.hasTransport(NetworkCapabilities.TRANSPORT_CELLULAR)) {
                        return getCellularIPAddress(context);
                    }
                } else {
                    return getWifiIPAddress(context);
                }
            }
        } catch (Exception e) {
            e.printStackTrace();
        }
        return null;
    }

    private String getWifiIPAddress(Context context) {
        final WifiManager wifiManager = (WifiManager) context.getSystemService(Context.WIFI_SERVICE);
        final int ip = wifiManager.getConnectionInfo().getIpAddress();
        return String.format("%d.%d.%d.%d", (ip & 0xff), (ip >> 8 & 0xff), (ip >> 16 & 0xff), (ip >> 24 & 0xff));
    }

    private String getCellularIPAddress(Context context) {
        // This method is more complex and may require additional permissions
        // For simplicity, this example does not include it
        return null;
    }
}

原生代码（iOS）：

在 AppDelegate.swift 中添加以下代码：

import UIKit
import Flutter

@UIApplicationMain
@objc class AppDelegate: FlutterAppDelegate {
  private let channel = "com.example/local_ip"

  override func application(
    _ application: UIApplication,
    didFinishLaunchingWithOptions launchOptions: [UIApplication.LaunchOptionsKey: Any]?
  ) -> Bool {
    GeneratedPluginRegistrant.register(with: self)
    let controller : FlutterViewController = window?.rootViewController as! FlutterViewController
    let methodChannel = FlutterMethodChannel(name: channel, binaryMessenger: controller.binaryMessenger)
    methodChannel.setMethodCallHandler({
      [weak self] (call: FlutterMethodCall, result: FlutterResult) -> Void in
      if call.method == "getLocalIP" {
        self?.getLocalIP(result: result)
      } else {
        result(FlutterMethodNotImplemented)
      }
    })
    return super.application(application, didFinishLaunchingWithOptions: launchOptions)
  }

  private func getLocalIP(result: @escaping FlutterResult<String>) {
    let task = URLSession.shared.dataTask(with: URL(string: "https://api.ipify.org?format=json")!) { data, response, error in
      if let data = data, let ip = String(data: data, encoding: .utf8)?.split(separator: ":").first {
        result(ip)
      } else {
        result(nil)
      }
    }
    task.resume()
  }
}