读取消息上下文

String conversationID = "si_user_a_user_b";
int before = 20; // 锚点之前拉取的条数
int after = 20;  // 锚点之后拉取的条数

OpenIMClient.getInstance().messageManager.fetchSurroundingMessages(
    new OnBase<Messages>() {
        @Override
        public void onSuccess(Messages messages) {
            List<Message> surrounding = messages.getData();
            // surrounding 包含目标锚点消息及其前后的上下文消息
        }

        @Override
        public void onError(int code, String error) {
            // 处理获取失败
        }
    },
    conversationID,
    targetMessage,
    ViewType.Search,
    before,
    after
);