从 Firebase 删除，通知数据集已更改();不刷新列表视图

Question

基本上从firebase删除对象后， notifyDataSetChanged()不会实时更新。我试图从适配器本身中删除对象，但也失败了。

回到此片段显示更新的列表，但我认为这是因为添加了孩子。这是我的代码。

public class ArchiveFragment extends Fragment {
    public static ArchiveFragment newInstance(Beer beer) {
        ArchiveFragment archiveFragment = new ArchiveFragment();
        if (beer != null) {
            Bundle args = new Bundle();
            args.putSerializable("beer", beer);
            archiveFragment.setArguments(args);
        }
        return archiveFragment;
    }
    public ArchiveFragment(){}
    private ArrayList<Beer> beerDB = new ArrayList<>();
    private ListView beerList;
    private RecyclerView beerRec;
    private DatabaseReference mDatabase;
    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {
        final View view = inflater.inflate(R.layout.archive_fragment, container, false);
        final Activity activity = getActivity();
        FirebaseUser user = FirebaseAuth.getInstance().getCurrentUser();
        beerList = (ListView)view.findViewById(R.id.beerList);
        final ArrayAdapter<Beer> arrayAdapter = new ArrayAdapter<Beer>(getActivity(), android.R.layout.simple_list_item_1,beerDB);
        mDatabase = FirebaseDatabase.getInstance().getReference().child("Users").child(user.getUid()).child("BeerList");
        beerList.setAdapter(arrayAdapter);
        beerList.setOnItemClickListener(new AdapterView.OnItemClickListener() {
            @Override
            public void onItemClick(AdapterView<?> adapterView, View view, int i, long l) {
                Object deletedBeer = beerList.getItemAtPosition(i);
                Beer delBeer = (Beer) deletedBeer;
                deleteBeer(delBeer.getKey());
            }
        });
        mDatabase.addChildEventListener(new ChildEventListener() {
            @Override
            public void onChildAdded(DataSnapshot dataSnapshot, String s) {
                Beer value = dataSnapshot.getValue(Beer.class);
                value.setKey(dataSnapshot.getKey());
                beerDB.add(value);
                arrayAdapter.notifyDataSetChanged();
            }
            @Override
            public void onChildChanged(DataSnapshot dataSnapshot, String s) {}
            @Override
            public void onChildRemoved(DataSnapshot dataSnapshot) {
                String key = dataSnapshot.getKey();
                beerDB.remove(key);
                arrayAdapter.notifyDataSetChanged();
            }
            @Override
            public void onChildMoved(DataSnapshot dataSnapshot, String s) {}
            @Override
            public void onCancelled(DatabaseError databaseError) {}
        });
        return view;
    }
    public void deleteBeer(String key){
        mDatabase.child(key).removeValue();
    }
}

Answer 1

您使用不正确的remove函数从ArrayList中删除项目。remove功能采用ArrayList中的项目索引，需要删除。但是在这里，当您从dataSnapshot获取键时，它与ArrayList的任何索引不匹配，因此实际上并未从ArrayList中删除该项目。因此，您需要这样更改onChildRemoved功能。

@Override
public void onChildRemoved(DataSnapshot dataSnapshot) {
    String key = dataSnapshot.getKey();
    for (int i = 0; i < beerDB.size(); i++) {
        // Find the item to remove and then remove it by index
        if (beerDB.get(i).key.equals(key)) {
            beerDB.remove(i);
            break;
        } 
    }
    arrayAdapter.notifyDataSetChanged();
}