如何从具有两个子层的Firebase实时数据检索数据到listView？

Question

如何在有两个孩子的事件文件夹中检索数据？ 我是android studio的新手...

示例代码如下：

database = FirebaseDatabase.getInstance();
    ref = database.getReference("Event");
    list = new ArrayList<String>();
    adapter = new ArrayAdapter<String>(this,R.layout.event_info,R.id.eventTitle,list);
    ref.addValueEventListener(new ValueEventListener() {
        @Override
        public void onDataChange(@NonNull DataSnapshot dataSnapshot) {
            for(DataSnapshot ds: dataSnapshot.getChildren())
            {
                eventInfo = ds.getValue(EventInfo.class);
                list.add(eventInfo.getTitle() + " \n " + eventInfo.getAddress() +
                        " \n " + eventInfo.getDescription() + " \n " + eventInfo.getImgURL() +
                        " \n " + eventInfo.getLatitude() + " \n " + eventInfo.getLongitude());
            }

            listView.setAdapter(adapter);
        }

Answer 1

当您遍历DataSnapshot.getChildren()时，每个孩子本身都是DataSnapshot。因此，您也可以遍历那个孩子的孩子。由于JSON中有两个动态级别，因此您的代码中需要两个嵌套循环：

ref = FirebaseDatabase.getInstance().getReference("Event");
ref.addValueEventListener(new ValueEventListener() {
    @Override
    public void onDataChange(@NonNull DataSnapshot dataSnapshot) {
        for(DataSnapshot userSnapshot: dataSnapshot.getChildren()) {
            for(DataSnapshot eventSnapshot: userSnapshot.getChildren()) {
                eventInfo = eventSnapshot.getValue(EventInfo.class);
                Log.d("Event", eventSnapshot.getKey());
                Log.d("Event", eventSnapshot.child("title").getValue(String.class));
            }
        }
    }
    ...