食品订购应用程序：RecyclerAdapter：与第一个产品列表进行通信，但不与第二个产品进行通信

Question

真的需要你的帮助，因为我一直在努力研究过去一周的解决方案。我目前正在YouTube上进行“订购食品”教程并且已经完成了第3部分，但这就是我被困住的地方（并且没有任何解决方案可供我使用）。

我的应用程序在登录方面工作正常，并点击第一个食物菜单类别然而，一旦我点击一个类别来查看子类别，我得到一个空白屏幕。没有“应用程序崩溃”错误，我能找到的最接近错误的内容如下：

11-20 18:39:03.495 1399-2097/? E/SurfaceFlinger: Failed to find layer (com.rykitech.www.homecookd/com.rykitech.www.eatit.SignIn#1) in layer parent (no-parent).
11-20 18:39:05.703 1762-1897/system_process E/TaskPersister: File error accessing recents directory (directory doesn't exist?).

但是，就像我说的，这不会使应用程序崩溃但只是显示一个空白的屏幕，请你能帮我找到问题吗？我还包括了我的JSON / Firebase文件的屏幕截图，这是我能说的完美：

这是我的Java文件：

food list.Java

public class FoodList extends AppCompatActivity {



    RecyclerView recyclerView;
    RecyclerView.LayoutManager layoutManager;

    FirebaseDatabase database;
    DatabaseReference foodList;

    String categoryId = "";

    FirebaseRecyclerAdapter<Food, FoodViewHolder> adapter;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_food_list);

        //Firebase
        database = FirebaseDatabase.getInstance();
        foodList = database.getReference("Food");

        recyclerView = (RecyclerView) findViewById(R.id.recycler_food);
        recyclerView.setHasFixedSize(true);
        layoutManager = new LinearLayoutManager(this);
        recyclerView.setLayoutManager(layoutManager);

        //get the intent here
        if(getIntent()!= null)
            categoryId = getIntent().getStringExtra("categoryId");
        if (categoryId != null   &&  !categoryId.isEmpty())
        {
            loadListFood(categoryId);

        }
    }

    private void loadListFood(String categoryId) {

        adapter = new FirebaseRecyclerAdapter<Food, FoodViewHolder>(Food.class,
                R.layout.food_item,
                FoodViewHolder.class,
                foodList.orderByChild("MenuId").equalTo(categoryId)//like: Select * from foods where menu ID
                ) {
            @Override
            protected void populateViewHolder(FoodViewHolder viewHolder, Food model, int position) {
                viewHolder.food_name.setText(model.getName());
                Picasso.with(getBaseContext()).load(model.getImage())
                        .into(viewHolder.food_image);

                final Food local = model;
                viewHolder.setItemClickListener(new ItemClickListener() {
                    @Override
                    public void onClick(View view, int position, boolean isLongCLick) {
                        Toast.makeText(FoodList.this, ""+local.getName(), Toast.LENGTH_SHORT).show();

                    }
                });

            }
        };

        recyclerView.setAdapter(adapter);
    }
}

home.Java

public class Home extends AppCompatActivity
        implements NavigationView.OnNavigationItemSelectedListener {

    FirebaseDatabase database;
    DatabaseReference category;

    TextView txtFullName;

    RecyclerView recycler_menu;
    RecyclerView.LayoutManager layoutManager;

    FirebaseRecyclerAdapter<Category,MenuViewHolder> adapter;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_home);


        Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
        toolbar.setTitle("Menu");
        setSupportActionBar(toolbar);

        //Init Firebase
        database = FirebaseDatabase.getInstance();
        category = database.getReference("Category");



        FloatingActionButton fab = (FloatingActionButton) findViewById(R.id.fab);
        fab.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                Snackbar.make(view, "Replace with your own action", Snackbar.LENGTH_LONG)
                        .setAction("Action", null).show();
            }
        });

        DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
        ActionBarDrawerToggle toggle = new ActionBarDrawerToggle(
                this, drawer, toolbar, R.string.navigation_drawer_open, R.string.navigation_drawer_close);
        drawer.addDrawerListener(toggle);
        toggle.syncState();

        NavigationView navigationView = (NavigationView) findViewById(R.id.nav_view);
        navigationView.setNavigationItemSelectedListener(this);

        //Set name for user
        View headerView = navigationView.getHeaderView(0);
        txtFullName = (TextView) headerView.findViewById(R.id.txtFullName);
        txtFullName.setText(Common.currentUser.getName());

        //Load Menu
        recycler_menu = (RecyclerView)findViewById(R.id.recycler_menu);
        recycler_menu.setHasFixedSize(true);
        layoutManager = new LinearLayoutManager(this);
        recycler_menu.setLayoutManager(layoutManager);

        loadMenu();


    }

    private void loadMenu() {

        adapter = new FirebaseRecyclerAdapter<Category, MenuViewHolder>(Category.class,R.layout.menu_item,MenuViewHolder.class,category) {
            @Override
            protected void populateViewHolder(MenuViewHolder viewHolder, Category model, int position) {
                viewHolder.txtMenuName.setText(model.getName());
                Picasso.with(getBaseContext()).load(model.getImage())
                        .into(viewHolder.imageView);

                final Category clickItem = model;
                viewHolder.setItemClickListener(new ItemClickListener() {
                    @Override
                    public void onClick(View view, int position, boolean isLongCLick) {
                       //Get category ID and send to new Activity
                        Intent foodList = new Intent(Home.this,FoodList.class);
                        //Because the category ID is key, we just the key of this item
                        foodList.putExtra("CategoryID",adapter.getRef(position).getKey());
                        startActivity(foodList);
                    }
                });

            }
        };
        recycler_menu.setAdapter(adapter);
    }

Answer 1

RecyclerView recyclerView;
RecyclerView.LayoutManager layoutManager;

FirebaseDatabase database;
DatabaseReference foodList;

String categoryId = "";

FirebaseRecyclerAdapter<Food, FoodViewHolder> adapter;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_food_list);

    // Firebase
    database = FirebaseDatabase.getInstance();
    foodList = database.getReference("Foods");

    recyclerView = (RecyclerView) findViewById(R.id.recycler_food);
    recyclerView.setHasFixedSize(true);
    layoutManager = new LinearLayoutManager(this);
    recyclerView.setLayoutManager(layoutManager);

    // Get Intent here
    if (getIntent() != null)
        categoryId = getIntent().getStringExtra("CategoryId");
    if (!categoryId.isEmpty() && categoryId != null) {
        Toast.makeText(this, "" + categoryId, Toast.LENGTH_SHORT).show();
        loadListFood(categoryId);
    }
}

private void loadListFood(String categoryId) {
    // Create query by Category Id
    Query searchByName = foodList.orderByChild("menuId").equalTo(categoryId);
    // create options with query
    FirebaseRecyclerOptions<Food> foodOptions = new FirebaseRecyclerOptions.Builder<Food>()
            .setQuery(searchByName, Food.class).build();

    adapter = new FirebaseRecyclerAdapter<Food, FoodViewHolder>(foodOptions) {
        @Override
        protected void onBindViewHolder(@NonNull FoodViewHolder viewHolder, int position,
                @NonNull final Food model) {

            viewHolder.food_name.setText(model.getName());
            Picasso.with(getBaseContext()).load(model.getImage()).into(viewHolder.food_image);

            final Food local = model;
            viewHolder.setItemClickListener(new ItemClickListener() {
                @Override
                public void onClick(View view, int position, boolean isLongClick) {
                    Toast.makeText(FoodList.this, "" + local.getName(), Toast.LENGTH_SHORT).show();
                }
            });
        }

        @NonNull
        @Override
        public FoodViewHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
            View itemView = LayoutInflater.from(parent.getContext()).inflate(R.layout.food_item, parent, false);
            return new FoodViewHolder(itemView);
        }
    };
    adapter.startListening();
    recyclerView.setAdapter(adapter);// Set Adapter for Recycler view is search result
}

@Override
protected void onStop() {
    super.onStop();
    adapter.stopListening();
}