RecyclerView RecyclerViewDataObserver未注册

Question

林有工作RecyclerView,SyncAdapter并greenrobot eventbus 当我SyncAdapter完成syincing我发布一条消息到消息总线:

EventBus.getDefault().post(new EventMessagesRefreshed());

在我的目标类中,我执行以下操作:

@Subscribe
public void onEvent(EventMessagesRefreshed event) {
    this.init();
}

在我的init()i中为recyclerview创建适配器并设置它:

public void init() {
    if(this.listRowParent != null) {
        this.adapter = new FragmentMessagesListAdapter(this.getActivity(), SingletonMessages.getInstance().getMessages());
        this.listRowParent.setAdapter(this.adapter);
    }
}

// listRowParent is my RecyclerView!

接收事件的片段位于选项卡视图的内部.因此,当我不在正确的目标选项卡中时,有多个选项卡,有时还有消息总线中的SyncAdapter帖子,EventMessagesRefreshed但由于它已注册,它会尝试调用init()并创建适配器并将其设置为RecyclerView.如果发生这种情况,我会收到以下错误:

Could not dispatch event: class EventMessagesRefreshed to subscribing class class FragmentMessagesList
java.lang.IllegalStateException: Observer android.support.v7.widget.RecyclerView$RecyclerViewDataObserver@2c3421a7 was not registered.
    at android.database.Observable.unregisterObserver(Observable.java:69)
    at android.support.v7.widget.RecyclerView$Adapter.unregisterAdapterDataObserver(RecyclerView.java:5688)
    at android.support.v7.widget.RecyclerView.setAdapterInternal(RecyclerView.java:873)
    at android.support.v7.widget.RecyclerView.setAdapter(RecyclerView.java:857)

所以我需要init()我的适配器,RecyclerView只有在RecyclerViewDataObserver注册时.

我怎样才能做到这一点？

Answer 1

您需要注册数据观察器以侦听来自同步适配器的数据更改.

mRecyclerViewAdapter.registerAdapterDataObserver(myObserver);

RecyclerView.AdapterDataObserver是您调用的通知方法的结果.因此,例如,如果在向适配器添加项目后调用notifyItemInserted(),则会调用onItemRangeInserted()

一个更详细的例子

protected void setupRecyclerView() {
    mAdapter = new MyAdapter(mItemList);
    mAdapter.registerAdapterDataObserver(new RecyclerView.AdapterDataObserver() {
        @Override
        public void onChanged() {
            super.onChanged();
            checkAdapterIsEmpty();
        }
    });

    mRecyclerView.setLayoutManager(new LinearLayoutManager(this));
    mRecyclerView.setHasFixedSize(true);

    mRecyclerView.setAdapter(mAdapter);
    checkAdapterIsEmpty();
}`

适配器可以发布描述特定更改的各种事件.并非所有适配器都支持所有更改类型,如果没有更具体的数据,某些适配器可能会回退到通用的"更改内容"事件.