Registrar class Null safety

A registrar for Flutter plugins implemented in Dart.

Plugins for the web platform are implemented in Dart and are registered with this class by code generated by the flutter tool when compiling the application.

This class implements BinaryMessenger to route messages from the framework to registered plugins.

Use this BinaryMessenger when creating platform channels in order for them to receive messages from the platform side. For example:

class MyPlugin {
  static void registerWith(Registrar registrar) {
    final MethodChannel channel = MethodChannel(
      'com.my_plugin/my_plugin',
      const StandardMethodCodec(),
      registrar, // the registrar is used as the BinaryMessenger
    );
    final MyPlugin instance = MyPlugin();
    channel.setMethodCallHandler(instance.handleMethodCall);
  }
  // ...
}