sendMessage method
Implementation
Future<void> sendMessage(AgoraRtmMessage message,
[bool? offline, bool? historical]) async {
final res = await _callNative("sendMessage", {
'message': message.text,
"offline": offline,
"historical": historical
});
if (res["errorCode"] != 0)
throw AgoraRtmChannelException(
"sendMessage failed errorCode:${res['errorCode']}", res['errorCode']);
}