New Android embedding, new and old plugins, or all old plugins.

MainActivity.java

// This example assumes that the developer is using the new Android embedding
// API, some plugins that use dart-side initialization, and some old plugins
// that have no concept of dart-side initialization.
//
// This example would be the same even if all used plugins were old (no dart-side
// initialization).
public class MainActivity extends FlutterActivity {
  @Override
  protected void onFlutterEngineCreated(@NonNull FlutterEngine engine) {
    // We register the GeneratedPluginLoader for the plugins that use
    // dart-side initialization.
    engine.setPluginLoader(new GeneratedPluginLoader());
    
    // The new Android embedding comes with a shim for old plugins. We use
    // that shim to initialize all the old-style plugins that don't support
    // dart-side initialization. The following line will cause all the old
    // plugins to be initialized right now and connected to the give engine.
    // This is the standard behavior today.
    new GeneratedShimPluginRegistrant().registerWith(engine);
  }
}