java - 如何从 Firebase 获取数据到 Recyclerview 中的片段？

Question

Java
这是我的应用程序片段的代码，当我运行它时，我的应用程序在启动应用程序时立即崩溃，得到客户主页片段它崩溃，在 logcat 中它显示 CustomerHomefragemnt 中存在错误所以这是我不是的代码能够解决它如果有人可以提供帮助，请回答。这是我的片段代码`

    public class CustomerHomeFragment extends Fragment implements 
    SwipeRefreshLayout.OnRefreshListener {

    RecyclerView recyclerView;
    private List<UpdateDishModel> updateDishModelList;
    private CustomerHomeAdapter adapter;
    String State, City, Sub;
    DatabaseReference dataaa, databaseReference;
    SwipeRefreshLayout swipeRefreshLayout;
    SearchView searchView;


    @Nullable
    @Override
    public View onCreateView(@NonNull LayoutInflater inflater, @Nullable ViewGroup container, 
    @Nullable Bundle savedInstanceState) {
        View v = inflater.inflate(R.layout.fragment_customerhome, null);
        setHasOptionsMenu(true);

        recyclerView = v.findViewById(R.id.recycle_menu);
        recyclerView.setHasFixedSize(true);
        Animation animation = AnimationUtils.loadAnimation(getContext(), R.anim.move);
        recyclerView.startAnimation(animation);
        recyclerView.setLayoutManager(new LinearLayoutManager(getContext()));
        updateDishModelList = new ArrayList<>();
        swipeRefreshLayout = (SwipeRefreshLayout) v.findViewById(R.id.swipelayout);
        swipeRefreshLayout.setOnRefreshListener(this);
        swipeRefreshLayout.setColorSchemeResources(R.color.colorPrimaryDark, R.color.green);


        swipeRefreshLayout.post(new Runnable() {
            @Override
            public void run() {
                swipeRefreshLayout.setRefreshing(true);
                String userid = FirebaseAuth.getInstance().getCurrentUser().getUid();
                dataaa = FirebaseDatabase.getInstance()
                           .getReference("Customer").child(userid);
                dataaa.addListenerForSingleValueEvent(new ValueEventListener() {
                    @Override
                    public void onDataChange(@NonNull DataSnapshot dataSnapshot) {
                        Customer cust = dataSnapshot.getValue(Customer.class);
                        State = cust.getState();
                        City = cust.getCity();
                        Sub = cust.getSuburban();
                        customermenu();
                    }


                    @Override
                    public void onCancelled(@NonNull DatabaseError databaseError) {

                    }
                });
            }
        });

        return v;
    }


    @Override
    public void onRefresh() {
        customermenu();
    }

    private void customermenu() {

        swipeRefreshLayout.setRefreshing(true);

        DatabaseReference databaseReference = 
    FirebaseDatabase.getInstance().getReference("FoodSupplyDetails")
          .child(State).child(City).child(Sub);
        databaseReference.addValueEventListener(new ValueEventListener() {
            @Override
            public void onDataChange(@NonNull DataSnapshot dataSnapshot) {
                updateDishModelList.clear();
                for (DataSnapshot snapshot : dataSnapshot.getChildren()) {
                    for (DataSnapshot snapshot1 : snapshot.getChildren()) {
                        UpdateDishModel updateDishModel = 
    snapshot1.getValue(UpdateDishModel.class);
                        updateDishModelList.add(updateDishModel);
                    }
                }
                adapter = new CustomerHomeAdapter(getContext(), updateDishModelList);
                recyclerView.setAdapter(adapter);
                swipeRefreshLayout.setRefreshing(false);

            }

            @Override
            public void onCancelled(@NonNull DatabaseError databaseError) {

                swipeRefreshLayout.setRefreshing(false);
            }
        });
        searchView.setOnQueryTextListener(new SearchView.OnQueryTextListener() {
            @Override
            public boolean onQueryTextSubmit(String query) {
                return false;
            }

            @Override
            public boolean onQueryTextChange(String newText) {
                search(newText);
                return true;
            }
        });

    }
    


    private void search(final String searchtext) {

        ArrayList<UpdateDishModel> mylist = new ArrayList<>();
        for (UpdateDishModel object : updateDishModelList) {
            if (object.getDishes().toLowerCase().contains(searchtext.toLowerCase())) {
                mylist.add(object);
            }
        }
        adapter = new CustomerHomeAdapter(getContext(), mylist);
        recyclerView.setAdapter(adapter);

    }


    @Override
    public void onCreateOptionsMenu(Menu menu, MenuInflater inflater) {
        inflater.inflate(R.menu.search, menu);
        MenuItem menuItem = menu.findItem(R.id.Searchdish);
        searchView = (SearchView) menuItem.getActionView();
        searchView.setQueryHint("Search Dish");


      }
    }
```


`here is my Homeadapter code`



    public class CustomerHomeAdapter extends  
             RecyclerView.Adapter<CustomerHomeAdapter.ViewHolder>
    {


    private Context mcontext;
    private List<UpdateDishModel>updateDishModellist;
    DatabaseReference databaseReference;

    public CustomerHomeAdapter(Context context,List<UpdateDishModel>updateDishModellist)
    {
        this.updateDishModellist=updateDishModellist;
        this.mcontext=context;
    }

    @NonNull
    @Override
    public ViewHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
        View view= 
            LayoutInflater.from(mcontext)
                 .inflate(R.layout.customer_menudish,parent,false);
        return new CustomerHomeAdapter.ViewHolder(view);
    }

    @Override
    public void onBindViewHolder(@NonNull final ViewHolder holder, int position) {

        final UpdateDishModel updateDishModel=updateDishModellist.get(position);
        Glide.with(mcontext).load(updateDishModel.getImageURL()).into(holder.imageView);
        holder.Dishname.setText(updateDishModel.getDishes());
        updateDishModel.getRandomUID();
        updateDishModel.getChefId();
        holder.price.setText("Price: ₹ " + updateDishModel.getPrice());
        holder.itemView.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {

                Intent intent=new Intent(mcontext,OrderDish.class);
                intent.putExtra("FoodMenu",updateDishModel.getRandomUID());
                intent.putExtra("ChefId",updateDishModel.getChefId());


                mcontext.startActivity(intent);
            }
        });
    }

    @Override
    public int getItemCount() {
        return updateDishModellist.size();
    }

    public class ViewHolder extends RecyclerView.ViewHolder {

        ImageView imageView;
        TextView Dishname,price;
        ElegantNumberButton additem;
        public ViewHolder(@NonNull View itemView) {
            super(itemView);

            imageView=itemView.findViewById(R.id.menu_image);
            Dishname=itemView.findViewById(R.id.dishname);
            price=itemView.findViewById(R.id.dishprice);
            additem=itemView.findViewById(R.id.number_btn);


        }
    }
   }

我认为此代码中有错误，因为我无法解决问题，请帮助我

private void customermenu() {
    
            swipeRefreshLayout.setRefreshing(true);
    
            DatabaseReference databaseReference = 
        FirebaseDatabase.getInstance().getReference("FoodSupplyDetails")
              .child(State).child(City).child(Sub);
            databaseReference.addValueEventListener(new ValueEventListener() {
                @Override
                public void onDataChange(@NonNull DataSnapshot dataSnapshot) {
                    updateDishModelList.clear();
                    for (DataSnapshot snapshot : dataSnapshot.getChildren()) {
                        for (DataSnapshot snapshot1 : snapshot.getChildren()) {
                            UpdateDishModel updateDishModel = 
        snapshot1.getValue(UpdateDishModel.class);
                            updateDishModelList.add(updateDishModel);
                        }
                    }
                    adapter = new CustomerHomeAdapter(getContext(), updateDishModelList);
                    recyclerView.setAdapter(adapter);
                    swipeRefreshLayout.setRefreshing(false);
    
                }
    
                @Override
                public void onCancelled(@NonNull DatabaseError databaseError) {
    
                    swipeRefreshLayout.setRefreshing(false);
                }
            });

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标签： javaandroidfirebase-realtime-databasefirebase-authentication

Answer 1

在运行查询之前，您应该确保这些值不为空。

if (State != null && City != null && Sub != null) {
  // Run your query here
} else {
  Log.d("TAG", "Data provided is null")
}

当您获取客户的信息时，请尝试记录并检查其中哪些为空：

String State, City, Sub;
//...

State = cust.getState();
City = cust.getCity();
Sub = cust.getSuburban();

Log.d("TAG", State);
Log.d("TAG", City);
Log.d("TAG", Sub);

// call customermenu now
customermenu();