======== MyPluginAsyncImpl.java ==========

MyPluginAsyncImpl implements PluginAsyncInterface {
                            @Override
                            public void onPostExecute(Object object) {
                              callback.onPostExecute(result);
                            }

                            @Override
                            public void onError(String errorMsg) {
                              callback.onError(errorMsg);
                            }
}

======== Main.java ==========
PluginMarker.this.setMarkerAnimation_(marker, markerAnimation, new MyPluginAsyncImpl());