Flutter插件开发流程原生端实现FlutterPlugin, MethodCallHandler接口，并分别重写on

创建Androidstudio创建插件项目，注意project type选择Plugin
原生端实现FlutterPlugin, MethodCallHandler接口，并分别重写onAttachedToEngine，onDetachedFromEngine，onMethodCall方法，onAttachedToEngine方法内初始化MethodChannel对象，onMethodCall方法回调根据方法名判断flutter调用的是哪个方法，并进行相应逻辑处理，然后通过success方法将结果回传给flutter，具体实现案例如下：

class DeviceUtilsPlugin: FlutterPlugin, MethodCallHandler {
  private lateinit var channel : MethodChannel

  override fun onAttachedToEngine(flutterPluginBinding: FlutterPlugin.FlutterPluginBinding) {
    channel = MethodChannel(flutterPluginBinding.binaryMessenger, "device_utils")
    channel.setMethodCallHandler(this)
  }

  override fun onMethodCall(call: MethodCall, result: Result) {
    if (call.method == "getDeviceVersion") {
      result.success("Android 1.0.1")
    } else {
      result.notImplemented()
    }
  }

  override fun onDetachedFromEngine(binding: FlutterPlugin.FlutterPluginBinding) {
    channel.setMethodCallHandler(null)
  }
}

flutter端继承PlatformInterface类，在此类定义你所需要的方法，具体实现案例如下：

abstract class DeviceUtilsPlatform extends PlatformInterface {
  /// Constructs a BatteryUtilsPlatform.
  BatteryUtilsPlatform() : super(token: _token);

  static final Object _token = Object();

  static DeviceUtilsPlatform _instance = MethodChannelDeviceUtils();

  static DeviceUtilsPlatform get instance => _instance;

  /// Platform-specific implementations should set this with their own
  /// platform-specific class that extends [BatteryUtilsPlatform] when
  /// they register themselves.
  static set instance(DeviceUtilsPlatform instance) {
    PlatformInterface.verifyToken(instance, _token);
    _instance = instance;
  }

  Future<String?> getDeviceVersion() {
    throw UnimplementedError('getDeviceVersion() has not been implemented.');
  }
}

定义MethodChannelDeviceUtils类，继承DeviceUtilsPlatform接口，在此类中创建MethodChannel对象，并重写DeviceUtilsPlatform方法，调用上述定义好的方法getDeviceVersion()，具体案例如下：

class MethodChannelDeviceUtils extends DeviceUtilsPlatform {
  /// The method channel used to interact with the native platform.
  @visibleForTesting
  final methodChannel = const MethodChannel('device_utils');

  @override
  Future<String?> getDeviceVersion() async {
    final version = await methodChannel.invokeMethod<String>('getDeviceVersion');
    return version;
  }
}

定义工具类，用于flutter调用插件方法

class BatteryUtils {
  Future<String?> getDeviceVersion() {
    return BatteryUtilsPlatform.instance.getDeviceVersion();
  }
}

引用插件：分为打包上传到pub.dev和本地直接引用，打包上传先运行flutter pub publish --dry-run确保插件配置正确，之后执行flutter pub publish 发布插件，本地引用可以直接通过pubspec.yaml引用插件的绝对路径，具体引用案例如下所示：

 device_utils:
    path: C:\Users\xxxx\AndroidStudioProjects\device_utils