Question

我正在构建一个活动应用程序，这是我每个活动的卡片模型：

现在这是我数据库中的事件数据。我有一个“events”节点（包含每个事件项）和一个“events-users”节点（其中包含参加该事件的每个用户项）。< / p>

要获取基本事件项（图像和名称），我有一个FirebaseRecyclerAdapter，它运行良好：

/**** EVENTS  EVENTS  EVENTS  EVENTS ****/
// Inflates events
RecyclerView mEventsRecyclerView = (RecyclerView) findViewById(R.id.activity_zone_events_recyclerview);
mEventsRecyclerView.setLayoutManager(new GridLayoutManager(ZoneActivity.this, 1));
DatabaseReference events = fDatabaseRoot.child("events");
mEventsAdapter = new FirebaseRecyclerAdapter<EventItem, EventItemHolder>(EventItem.class, R.layout.item_event, EventItemHolder.class, events) {
    @Override
    protected void populateViewHolder(final EventItemHolder eventItemHolder, final EventItem event, final int position) {

        // Sets event image
        eventItemHolder.setEventImage(event.getEventImage());

        // Sets event name
        eventItemHolder.setEventName(event.getEventName());

        // Sets event OnClickListener
        eventItemHolder.eventCard.setOnClickListener(new OnClickListener() {
            @Override
            public void onClick(View v) {
                // Opens EventActivity
                Intent eventActivity = new Intent(ZoneActivity.this, EventActivity.class);
                startActivity(eventActivity);
            }

        }
    });

};
mEventsRecyclerView.setAdapter(mEventsAdapter);

问题是我不知道如何在每张卡内获取用户项目（与会者）。我尝试在我创建的FirebaseRecyclerAdapter中初始化另一个FirebaseRecyclerAdapter但是当我打开相应的活动时应用程序中断...这就是我尝试过的：

/**** EVENTS  EVENTS  EVENTS  EVENTS ****/
// Inflates events
RecyclerView mEventsRecyclerView = (RecyclerView) findViewById(R.id.activity_zone_events_recyclerview);
mEventsRecyclerView.setLayoutManager(new GridLayoutManager(ZoneActivity.this, 1));
DatabaseReference events = fDatabaseRoot.child("events");
mEventsAdapter = new FirebaseRecyclerAdapter<EventItem, EventItemHolder>(EventItem.class, R.layout.item_event, EventItemHolder.class, events) {
    @Override
    protected void populateViewHolder(final EventItemHolder eventItemHolder, final EventItem event, final int position) {

        // Sets event image
        eventItemHolder.setEventImage(event.getEventImage());

        // Sets event name
        eventItemHolder.setEventName(event.getEventName());

        // Sets event OnClickListener
        eventItemHolder.eventCard.setOnClickListener(new OnClickListener() {
            @Override
            public void onClick(View v) {
                // Opens EventActivity
                Intent eventActivity = new Intent(ZoneActivity.this, EventActivity.class);
                startActivity(eventActivity);
            }

        /**** EVENT-ATTENDEES  EVENT-ATTENDEES  EVENT-ATTENDEES  EVENT-ATTENDEES ****/
        // Inflates event's attendees
        RecyclerView mAttendeesRecyclerView = (RecyclerView) findViewById(R.id.item_event_attendees_recyclerview);
        mAttendeesRecyclerView.setLayoutManager(new GridLayoutManager(ZoneActivity.this, 1));
        mAttendeesAdapter = new FirebaseRecyclerAdapter<UserItem, UserItemHolder>(UserItem.class, R.layout.item_user, UserItemHolder.class, fDatabaseRoot.child("zones-events").child(zoneKey)) {
            @Override
            protected void populateViewHolder(final UserItemHolder userItemHolder, final UserItem user, final int position) {

                // Sets attendee image
                userItemHolder.setUserImage(user.getUserImage());

            }

        };
        mAttendeesRecyclerView.setAdapter(mAttendeesAdapter);

    }

};
mEventsRecyclerView.setAdapter(mEventsAdapter);

这是错误：

02-27 19:18:53.783 1050-1050/? E/UncaughtException:  java.lang.NullPointerException: Attempt to invoke virtual method 'void android.support.v7.widget.RecyclerView.setLayoutManager(android.support.v7.widget.RecyclerView$LayoutManager)' on a null object reference
                                                    at com.whatudu.whatudu.ZoneActivity$2$1$1.populateViewHolder(ZoneActivity.java:208)
                                                    at com.whatudu.whatudu.ZoneActivity$2$1$1.populateViewHolder(ZoneActivity.java:141)
                                                    at com.firebase.ui.database.FirebaseRecyclerAdapter.onBindViewHolder(FirebaseRecyclerAdapter.java:184)
                                                    at android.support.v7.widget.RecyclerView$Adapter.onBindViewHolder(RecyclerView.java:5825)
                                                    at android.support.v7.widget.RecyclerView$Adapter.bindViewHolder(RecyclerView.java:5858)
                                                    at android.support.v7.widget.RecyclerView$Recycler.getViewForPosition(RecyclerView.java:5094)
                                                    at android.support.v7.widget.RecyclerView$Recycler.getViewForPosition(RecyclerView.java:4970)
                                                    at android.support.v7.widget.LinearLayoutManager$LayoutState.next(LinearLayoutManager.java:2029)
                                                    at android.support.v7.widget.GridLayoutManager.layoutChunk(GridLayoutManager.java:541)
                                                    at android.support.v7.widget.LinearLayoutManager.fill(LinearLayoutManager.java:1377)
                                                    at android.support.v7.widget.LinearLayoutManager.onLayoutChildren(LinearLayoutManager.java:578)
                                                    at android.support.v7.widget.GridLayoutManager.onLayoutChildren(GridLayoutManager.java:170)
                                                    at android.support.v7.widget.RecyclerView.dispatchLayoutStep2(RecyclerView.java:3315)
                                                    at android.support.v7.widget.RecyclerView.onMeasure(RecyclerView.java:2843)

任何形式的帮助或提示（如果之前有人这样做过）将非常感谢！我知道这是可能的，我只是不知道该怎么做！ :(

非常感谢你。

P.S。选择GridLayoutManager作为布局样式，因为这是我之前所做的。

FirebaseRecyclerAdapter中的FirebaseRecyclerAdapter

0 个答案: