String discussionSubject = txtSubject.getText().toString();
String discussionMessage = txtMsg.getText().toString();

if (lr!=null)
{
    ForumDiscussionDatum data = new ForumDiscussionDatum();
    data.setMessage(discussionMessage);
    data.setSubject(discussionSubject);
    int id = Integer.parseInt(idForum); //extra of another activity, getted onCreate()

    moodle.forum_add_discussion(lr.getClient(), lr.getSessionkey(), id, data);
}