Flutter兼容性绑定插件bindings_compatible的使用

在Flutter开发中，bindings_compatible 包主要用于处理平台特定的代码绑定，以确保在不同平台（如iOS和Android）上具有一致的API和行为。虽然 Flutter 本身已经提供了很多跨平台的功能，但在某些情况下，你可能需要直接访问平台特定的功能或API。这时，bindings_compatible 包就显得非常有用。

下面是一个简单的示例，展示了如何在Flutter中使用bindings_compatible来访问平台特定的功能。不过，需要注意的是，bindings_compatible 包本身并不直接提供API，而是通过dart:ui和其他平台通道机制来实现跨平台兼容性。因此，这里我们会结合MethodChannel来演示如何实现这一功能。

1. 设置Flutter项目

首先，确保你的Flutter项目已经创建并配置好。如果还没有，可以使用以下命令创建一个新的Flutter项目：

flutter create my_flutter_app
cd my_flutter_app

2. 在Dart代码中定义MethodChannel

在lib目录下创建一个新的Dart文件，例如platform_bindings.dart，并在其中定义与平台通信的MethodChannel。

import 'package:flutter/services.dart';

class PlatformBindings {
  static const MethodChannel _channel = MethodChannel('com.example.my_flutter_app/platform_bindings');

  // 定义一个方法来获取平台版本（这是一个示例，具体实现取决于平台端代码）
  static Future<String?> getPlatformVersion() async {
    final String? version = await _channel.invokeMethod('getPlatformVersion');
    return version;
  }
}

3. 在Android端实现MethodChannel

在android/app/src/main/kotlin/.../MainActivity.kt（或Java目录下的相应文件）中添加对MethodChannel的响应。

package com.example.my_flutter_app

import android.os.Bundle
import io.flutter.embedding.android.FlutterActivity
import io.flutter.embedding.engine.FlutterEngine
import io.flutter.plugin.common.MethodChannel

class MainActivity: FlutterActivity() {
    private val CHANNEL = "com.example.my_flutter_app/platform_bindings"

    override fun configureFlutterEngine(flutterEngine: FlutterEngine) {
        super.configureFlutterEngine(flutterEngine)
        MethodChannel(flutterEngine.dartExecutor.binaryMessenger, CHANNEL).setMethodCallHandler { call, result ->
            if (call.method == "getPlatformVersion") {
                result.success(android.os.Build.VERSION.RELEASE) // 返回Android版本作为示例
            } else {
                result.notImplemented()
            }
        }
    }
}

4. 在iOS端实现MethodChannel

在ios/Runner/AppDelegate.swift中添加对MethodChannel的响应。

import UIKit
import Flutter

@UIApplicationMain
@objc class AppDelegate: FlutterAppDelegate {
  override func application(
    _ application: UIApplication,
    didFinishLaunchingWithOptions launchOptions: [UIApplication.LaunchOptionsKey: Any]?
  ) -> Bool {
    GeneratedPluginRegistrant.register(with: self)
    
    let controller : FlutterViewController = window?.rootViewController as! FlutterViewController
    let channel = FlutterMethodChannel(name: "com.example.my_flutter_app/platform_bindings", binaryMessenger: controller.binaryMessenger)
    channel.setMethodCallHandler {
      (call: FlutterMethodCall, result: @escaping FlutterResult) in
      if call.method == "getPlatformVersion" {
        let version = UIDevice.current.systemVersion
        result(version)
      } else {
        result(FlutterMethodNotImplemented)
      }
    }
    
    return super.application(application, didFinishLaunchingWithOptions: launchOptions)
  }
}

5. 在Flutter界面中使用PlatformBindings

最后，在你的Flutter应用的界面中使用PlatformBindings来获取平台版本并显示。

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

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

class MyApp extends StatefulWidget {
  @override
  _MyAppState createState() => _MyAppState();
}

class _MyAppState extends State<MyApp> {
  String? _platformVersion = 'Unknown';

  @override
  void initState() {
    super.initState();
    _getPlatformVersion();
  }

  // Platform messages are asynchronous, so we initialize in an async method.
  Future<void> _getPlatformVersion() async {
    String? version;
    // Platform messages may fail, so we use a try-catch block.
    try {
      version = await PlatformBindings.getPlatformVersion();
    } on PlatformException {
      version = 'Failed to get platform version.';
    }

    // If the widget was removed from the tree while the asynchronous platform
    // message was in flight, we want to discard the reply rather than calling
    // setState to update our non-existent appearance.
    if (!mounted) return;

    setState(() {
      _platformVersion = version;
    });
  }

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      home: Scaffold(
        appBar: AppBar(
          title: const Text('Platform Version'),
        ),
        body: Center(
          child: Text('Running on: $_platformVersion\n'),
        ),
      ),
    );
  }
}

通过上述步骤，你已经创建了一个简单的Flutter应用，它使用MethodChannel与原生平台代码进行通信，并展示了如何在Flutter中处理平台特定的功能。尽管示例中并未直接使用bindings_compatible包，但这种方法是实现跨平台兼容性绑定的常用方式。