feat：参照研听的基础工程

packages/flutter_paid/lib/flutter_paid.dart

@@ -0,0 +1,11 @@
+import 'flutter_paid_platform_interface.dart';
+
+class FlutterPaid {
+  Future<String?> getPlatformVersion() {
+    return FlutterPaidPlatform.instance.getPlatformVersion();
+  }
+
+  Future<String?> paid() {
+    return FlutterPaidPlatform.instance.paid();
+  }
+}

packages/flutter_paid/lib/flutter_paid_method_channel.dart

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+import 'package:flutter/foundation.dart';
+import 'package:flutter/services.dart';
+
+import 'flutter_paid_platform_interface.dart';
+
+/// An implementation of [FlutterPaidPlatform] that uses method channels.
+class MethodChannelFlutterPaid extends FlutterPaidPlatform {
+  /// The method channel used to interact with the native platform.
+  @visibleForTesting
+  final methodChannel = const MethodChannel('flutter_paid');
+
+  @override
+  Future<String?> getPlatformVersion() async {
+    final version = await methodChannel.invokeMethod<String>('getPlatformVersion');
+    return version;
+  }
+
+  @override
+  Future<String?> paid() async {
+    final paid = await methodChannel.invokeMethod<String>('paid');
+    return paid;
+  }
+}

packages/flutter_paid/lib/flutter_paid_platform_interface.dart

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+import 'package:plugin_platform_interface/plugin_platform_interface.dart';
+
+import 'flutter_paid_method_channel.dart';
+
+abstract class FlutterPaidPlatform extends PlatformInterface {
+  /// Constructs a FlutterPaidPlatform.
+  FlutterPaidPlatform() : super(token: _token);
+
+  static final Object _token = Object();
+
+  static FlutterPaidPlatform _instance = MethodChannelFlutterPaid();
+
+  /// The default instance of [FlutterPaidPlatform] to use.
+  ///
+  /// Defaults to [MethodChannelFlutterPaid].
+  static FlutterPaidPlatform get instance => _instance;
+
+  /// Platform-specific implementations should set this with their own
+  /// platform-specific class that extends [FlutterPaidPlatform] when
+  /// they register themselves.
+  static set instance(FlutterPaidPlatform instance) {
+    PlatformInterface.verifyToken(instance, _token);
+    _instance = instance;
+  }
+
+  Future<String?> getPlatformVersion() {
+    throw UnimplementedError('platformVersion() has not been implemented.');
+  }
+  Future<String?> paid() {
+    throw UnimplementedError('platformVersion() has not been implemented.');
+  }
+}