RecyclerView 未显示从 API 获取的数据

Question

我正在创建一个应用程序，该应用程序根据他们使用SpoonAcular API的成分显示用户食谱 该应用程序获取了用户当前在 Firebase 实时数据库上拥有的成分，并使用数据来获取食谱。 我已经创建了获取数据所需的所有适配器，但应用程序没有按应有的方式显示 recyclerView。 这是我的代码

RequestManager.java

public class RequestManager {

    Context context;
    Retrofit retrofit = new Retrofit.Builder()
            .baseUrl("https://api.spoonacular.com/")
            .addConverterFactory(GsonConverterFactory.create())
            .build();

    public RequestManager(Context context){
        this.context = context;
    }

    public void getRecipeByIngredient(RecipeByIngredientListener listener, List <String> IngredientList){
        CallRecipeByIngredient callRecipeByIngredient = retrofit.create(CallRecipeByIngredient.class);


        Call <List<RecipeIngredResponse>> call = callRecipeByIngredient.callRecipeByIngredient(context.getString(R.string.API), IngredientList, "20");
        call.enqueue(new Callback<List<RecipeIngredResponse>>() {
            @Override
            public void onResponse(Call<List<RecipeIngredResponse>> call, Response<List<RecipeIngredResponse>> response) {
                if(!response.isSuccessful()){
                    listener.didError(response.message());
                    return;
                }
                listener.didFetch(response.body(), response.message());
            }

            @Override
            public void onFailure(Call<List<RecipeIngredResponse>> call, Throwable t) {
                listener.didError(t.getMessage());
            }
        });
    }

    private interface CallRecipeByIngredient{
        @GET("recipes/findByIngredients")
        Call<List<RecipeIngredResponse>> callRecipeByIngredient(
                @Query("apiKey") String apiKey,
                @Query("ingredients") List <String> Ingredient,
                @Query("number") String number
        );
    }
}

RecipeByIngredientListener

public interface RecipeByIngredientListener {
    void didFetch(List<RecipeIngredResponse> response, String message);
    void didError(String message);
}

RecipeByIngredientAdapter

public class RecipeByIngredientAdapter extends RecyclerView.Adapter<RecipeByIngredientViewHolder> {

    Context context;
    List<RecipeIngredResponse> list;

    public RecipeByIngredientAdapter(Context context, List<RecipeIngredResponse> list) {
        this.context = context;
        this.list = list;
    }

    @NonNull
    @Override
    public RecipeByIngredientViewHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
        return new RecipeByIngredientViewHolder(LayoutInflater.from(context).inflate(R.layout.list_recipebyingred , parent, false));
    }

    @SuppressLint("SetTextI18n")
    @Override
    public void onBindViewHolder(@NonNull RecipeByIngredientViewHolder holder, int position) {
        holder.recipeName.setText(list.get(position).title);
        holder.missedIngred.setText(list.get(position).missedIngredientCount + " Missed Ingredient");
        holder.likes.setText(list.get(position).likes + " Likes");
        Picasso.get().load(list.get(position).image).into(holder.recipeImage);
    }

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

class RecipeByIngredientViewHolder extends RecyclerView.ViewHolder{

    ImageView recipeImage;
    TextView recipeName, missedIngred, likes;

    public RecipeByIngredientViewHolder(@NonNull View itemView) {
        super(itemView);

        recipeImage = itemView.findViewById(R.id.recipeImage);
        recipeName = itemView.findViewById(R.id.recipeName);
        missedIngred = itemView.findViewById(R.id.missedIngred);
        likes = itemView.findViewById(R.id.likes);
    }
}

首页.java（片段）

RandomRecipeAdapter randomRecipeAdapter;
RequestManager manager;
RecyclerView recyclerView, recyclerFromYourFridge;
RecipeByIngredientAdapter recipeByIngredientAdapter;

@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
                         Bundle savedInstanceState) {

    // Inflate the layout for this fragment
    View v =  inflater.inflate(R.layout.fragment_home, container, false);

    manager = new RequestManager(getContext());
    manager.getRandomRecipe(randomRecipeResponseListener);

    recyclerFromYourFridge = (RecyclerView) v.findViewById(R.id.recyclerFromYourFridge);
    //get ingredient from database
    List<String> Ingredient =  new ArrayList<>();
    FirebaseAuth mAuth = FirebaseAuth.getInstance();
    String currentUser = mAuth.getCurrentUser().getUid();
    DatabaseReference reference = FirebaseDatabase.getInstance().getReference().child("Ingredient").child(currentUser);
    reference.get().addOnCompleteListener(new OnCompleteListener<DataSnapshot>() {
        @Override
        public void onComplete(@NonNull Task<DataSnapshot> task) {
            if(task.isSuccessful()){
                for (DataSnapshot userSnapshot : task.getResult().getChildren()){
                    Ingredient.add(userSnapshot.getKey());
                }
            }
        }
    });

    manager.getRecipeByIngredient(recipeByIngredientListener , Ingredient);

    recyclerView = (RecyclerView) v.findViewById(R.id.randomRecipeRecycler);
    return v;

}

private final RecipeByIngredientListener recipeByIngredientListener = new RecipeByIngredientListener() {
    @Override
    public void didFetch(List<RecipeIngredResponse> response, String message) {

        recyclerFromYourFridge.setHasFixedSize(true);
        recyclerFromYourFridge.setLayoutManager(new LinearLayoutManager(getContext(), LinearLayoutManager.VERTICAL, false));
        recipeByIngredientAdapter = new RecipeByIngredientAdapter(getContext(), response);
        recyclerFromYourFridge.setAdapter(recipeByIngredientAdapter);
    }

    @Override
    public void didError(String message) {
        Toast.makeText(getContext(), message, Toast.LENGTH_SHORT).show();
    }
};

很确定应用程序从 Firebase 获取成分没有任何问题，因为我已经对其进行了测试，并且 api 能够通过使用 ArrayList 获取配方。 这段代码有什么问题吗？

Answer 1

问题是因为对 Firebase 数据库的调用是异步的，如果调用 addOnCompleteListener 之外的值可以为空

将 reference.get().addOnCompleteListener 更改为：

reference.get().addOnCompleteListener(new OnCompleteListener<DataSnapshot>() {
    @Override
    public void onComplete(@NonNull Task<DataSnapshot> task) {
        if(task.isSuccessful()){
            List<String> Ingredient =  new ArrayList<>();
            for (DataSnapshot userSnapshot : task.getResult().getChildren()){
                Ingredient.add(userSnapshot.getKey());
            }
            manager.getRecipeByIngredient(recipeByIngredientListener , Ingredient);
        }
    }
});