新版的SDK,究竟该怎么获取群组的成员列表?

需求:有一个群组的详情界面,我在这个界面需要展示出已经加入了群组的成员,也就是要拿到群组成员列表.
 
查阅开发文档,使用如下方法:

List memberList = new ArrayList<>();

EMCursorResult result = null;

final int pageSize = 20;

do {

    result = EMClient.getInstance().groupManager().fetchGroupMembers(groupId,

        result != null ? result.getCursor() : "", pageSize);

    memberList.addAll(result.getData());

} while (result.getData().size() == pageSize);

 
 
报错:

05-02 17:34:25.179 24720-27635/com.onion W/System.err: com.hyphenate.exceptions.HyphenateException: User has not joined the group

05-02 17:34:25.180 24720-27635/com.onion W/System.err:     at com.hyphenate.chat.EMGroupManager.handleError(Unknown Source)

05-02 17:34:25.181 24720-27635/com.onion W/System.err:     at com.hyphenate.chat.EMGroupManager.fetchGroupMembers(Unknown Source)

05-02 17:34:25.181 24720-27635/com.onion W/System.err:     at com.onion.view.activity.groups.GroupsActivity$9.call(GroupsActivity.java:364)

05-02 17:34:25.181 24720-27635/com.onion W/System.err:     at com.onion.view.activity.groups.GroupsActivity$9.call(GroupsActivity.java:356)

05-02 17:34:25.181 24720-27635/com.onion W/System.err:     at rx.Observable.unsafeSubscribe(Observable.java:8666)

05-02 17:34:25.182 24720-27635/com.onion W/System.err:     at rx.internal.operators.OperatorSubscribeOn$1.call(OperatorSubscribeOn.java:94)

05-02 17:34:25.182 24720-27635/com.onion W/System.err:     at rx.internal.schedulers.CachedThreadScheduler$EventLoopWorker$1.call(CachedThreadScheduler.java:220)

05-02 17:34:25.182 24720-27635/com.onion W/System.err:     at rx.internal.schedulers.ScheduledAction.run(ScheduledAction.java:55)

05-02 17:34:25.182 24720-27635/com.onion W/System.err:     at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:423)

05-02 17:34:25.182 24720-27635/com.onion W/System.err:     at java.util.concurrent.FutureTask.run(FutureTask.java:237)

05-02 17:34:25.183 24720-27635/com.onion W/System.err:     at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.access$201(ScheduledThreadPoolExecutor.java:154)

05-02 17:34:25.183 24720-27635/com.onion W/System.err:     at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.run(ScheduledThreadPoolExecutor.java:269)

05-02 17:34:25.183 24720-27635/com.onion W/System.err:     at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1113)

05-02 17:34:25.187 24720-27635/com.onion W/System.err:     at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:588)

05-02 17:34:25.187 24720-27635/com.onion W/System.err:     at java.lang.Thread.run(Thread.java:818)

观察报错:
    是因为当前用户没有加入群组,所以不能获取到群组成员列表.
 
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于是,放弃上面的方法,通过查阅API文档,修改为下面的方法:

// 先从服务器拿到群组对象

EMGroup group = EMClient.getInstance().groupManager().getGroupFromServer(groupId);

// 拿出群组成员数量

mMemberCount = group.getMemberCount();

// 拿出群组成员

List members = group.getMembers();

// 遍历集合

for (String id : members) {

	subscriber.onNext(id);

}

subscriber.onCompleted();

这个方法,获取的成员数量是正确的,但是成员列表集合却永远都是零的.
我记得之前的版本的SDK是可以这么获取成员列表集合的啊...
 
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好,接下来,是我的提问:
    现在版本的SDK,我究竟该用什么方法获取群组的成员列表(在没有加入该群组的情况下)?