getGroupAnnouncementFromServer method
从服务器获取群公告
Implementation
Future<String?> getGroupAnnouncementFromServer(String groupId) async {
Map req = {'groupId': groupId};
Map result = await _channel.invokeMethod(
EMSDKMethod.getGroupAnnouncementFromServer, req);
EMError.hasErrorFromResult(result);
return result[EMSDKMethod.getGroupAnnouncementFromServer];
}