PageHelper插件实现一对多查询时的分页问题

<resultMap id="BaseMap" type="com.xx.oo.Activity">
  <id column="id" property="id" jdbcType="INTEGER"/>
    ....
</resultMap>

<resultMap id="ResultMap" type="com.xx.oo.Activity" extends="BaseMap">
  <collection property="templates" ofType="com.xx.oo.Template">
    <id column="pt_id" property="id" jdbcType="INTEGER"/>
    <result column="pt_title" property="title" jdbcType="VARCHAR"/>
  </collection>
</resultMap>

<resultMap id="RichResultMap" type="com.xx.oo.Activity" extends="BaseMap">
  <!--property：对应JavaBean中的字段-->
  <!--ofType：对应JavaBean的类型-->
  <!--javaType：对应返回值的类型-->
  <!--column：对应数据库column的字段，不是JavaBean中的字段-->
  <!--select：对应查询子集的sql-->
  <collection property="templates" ofType="com.xx.oo.Template" javaType="java.util.List" column="id" select="queryTemplateById">
    <id column="pt_id" property="id" jdbcType="INTEGER"/>
    <result column="pt_title" property="title" jdbcType="VARCHAR"/>
  </collection>
</resultMap>

<resultMap id="template" type="com.xx.oo.Template">
  <id column="pt_id" property="id" jdbcType="INTEGER"/>
  <result column="pt_title" property="title" jdbcType="VARCHAR"/>
</resultMap>

<!--这里的#{id}参数就是collection中定义的column字段-->
<select id="queryTemplateById" parameterType="java.lang.Integer" resultMap="template">
  select id pt_id, title pt_title
  from t_activity_template where is_delete=0 and activity_id = #{id}
  order by sort_number desc
</select>
<select id="queryByPage" parameterType="com.xx.oo.ActivityPageRequest" resultMap="RichResultMap">
  SELECT t.*,t1.real_name creator_name
  FROM t_activity t
  left join user t1 on t1.user_id = t.creator
  <where>
    t.is_delete = 0
    <if test="criteria != null and criteria.length()>0">AND (t.activity_name like concat("%",#{criteria},"%"))</if>
  </where>
  ORDER BY t.id desc
</select>

<select id="queryById" parameterType="java.lang.Integer" resultMap="ResultMap">
  SELECT t.*, t6.id pt_id, t1.title pt_title
  FROM t_activity t
  left join t_activity_template t1 on t.id=t6.activity_id and t1.is_delete=0
  WHERE t.is_delete = 0 AND t.id = #{id}
</select>