认识smack3.0.4基本对象——From

From收集的数据形式，可以是以下类型：

form -> 表示From需要填充.
submit -> 表示From已经填充，这是从From中返回的数据
cancel -> 表示From已经取消，告诉请求者连接信息. .
result -> 表示数据结果来自From, 或者其他查询.

不同From决定不同的操作，比如：如果From类型“提交”，则只能设置答复。

Represents a Form for gathering data. The form could be of the following types:
form -> Indicates a form to fill out.
submit -> The form is filled out, and this is the data that is being returned from the form.
cancel -> The form was cancelled. Tell the asker that piece of information.
result -> Data results being returned from a search, or some other query.
Depending of the form's type different operations are available. For example, it's only possible to set answers if the form is of type "submit".