Question

我需要对我的数据库执行查询以获取一些ID，然后使用这些ID对Realm DB执行另一个查询，并将结果返回到用于创建UI的适配器。我的问题是适配器是在onCreatView（主线程）中创建的，我需要让等待查询结果。你知道我该怎么办？非常感谢：）

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

    Realm realm = Realm.getDefaultInstance();
    cardList = new ArrayList(realm.where(Card.class).findAll().sort("rarity"));
    View rootView = inflater.inflate(R.layout.inventory_fragment_layout, null);
    RecyclerView recyclerView = rootView.findViewById(R.id.inventory_recycler);
    recyclerView.setLayoutManager(new GridLayoutManager(this.getContext(), 2));
    adapter = new inventoryFragmentRecyclerAdapter(this.getContext(), getCards()); <----- getCards() is used here.
    adapter.setClickListener(this);
    recyclerView.setAdapter(adapter);
    TextView topText = rootView.findViewById(R.id.inv_topText);
    topText.setTypeface(Typeface.createFromAsset(getActivity().getAssets(), "fonts/Square.ttf"));

    return rootView;
}



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public List<Card> getCards() { //It is used when adapter is created, and it need to contain all cards to display

    //Realm realm = Realm.getDefaultInstance();

    String urlToGet = "myurl";
    String user_name = settings.getString("username", null);

    OkHttpClient client = new OkHttpClient();

    RequestBody formBody = new FormBody.Builder()
            .add("user_name", user_name)
            .build();

    Request request = new Request.Builder()
            .url(urlToGet)
            .post(formBody)
            .build();

    client.newCall(request).enqueue(new Callback() {
        @Override
        public void onFailure(Call call, IOException e) {
            e.printStackTrace();
        }

        @Override
        public void onResponse(Call call, final Response response) throws IOException {
            if (!response.isSuccessful()) {
                throw new IOException("Unexpected code " + response);
            }

            responseCardInInventory = response.body().string();

            handler.post(new Runnable() {
                @Override
                public void run() {

                    List<CardInInv> cardListInInv = new ArrayList<>();

                    Gson gson = new Gson();
                    CardInInventory civ = gson.fromJson(responseCardInInventory, CardInInventory.class);
                    cardListInInv = getCards(civ);

                    //HERE I NEED TO USE REALM TO EXECUTE A QUERY USING cardListInInv


                }
            });
        }
    });

    //HERE I NEED TO RETURN THE RESULT OF THE QUERY EXECUTED BEFORE
    return cardsIninv;

}

编辑1：Hre是我的适配器代码

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

private List<Card> dataCard = new ArrayList<>();
private LayoutInflater mInflater;
private ItemClickListener mClickListener;


// data is passed into the constructor
public inventoryFragmentRecyclerAdapter(Context context, List<Card> data) {
    this.mInflater = LayoutInflater.from(context);
    this.dataCard = data;
}

// inflates the cell layout from xml when needed
@Override
public ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
    View view = mInflater.inflate(R.layout.inventory_rw, parent, false);
    return new ViewHolder(view);
}

// binds the data to the in each cell
@Override
public void onBindViewHolder(ViewHolder holder, int position) {
    holder.cardImage.setImageBitmap(BitmapFactory.decodeByteArray(dataCard.get(position).getCardImage(), 0, dataCard.get(position).getCardImage().length));
}

// total number of cells
@Override
public int getItemCount() {
    return dataCard.size();
}


// stores and recycles views as they are scrolled off screen
public class ViewHolder extends RecyclerView.ViewHolder implements View.OnClickListener {
    ImageView cardImage;

    //instanzio le componenti della pagina

    ViewHolder(View itemView) {
        super(itemView);

        cardImage = itemView.findViewById(R.id.inv_rw_cardimage);
        itemView.setOnClickListener(this);

    }

    @Override
    public void onClick(View view) {
        if (mClickListener != null) mClickListener.onItemClick(view, getAdapterPosition());
    }
}

// convenience method for getting data at click position
Card getItem(int id) {
    return dataCard.get(id);
}

// allows clicks events to be caught
public void setClickListener(ItemClickListener itemClickListener) {
    this.mClickListener = itemClickListener;
}

// parent activity will implement this method to respond to click events
public interface ItemClickListener {
    void onItemClick(View view, int position);
}
}

Answer 1

将查询移至适配器并使用空列表启动适配器。在构造函数的末尾进行查询调用。成功完成查询后，通知适配器它已更改，并在查询结束时使用新数据处理更改。所以在这之后你的适配器看起来像这样。

public inventoryFragmentRecyclerAdapter(Context context, List<Card> data) {
    this.mInflater = LayoutInflater.from(context);
    getCards();
}

public void getCards() { //It is used when adapter is created, and it need to contain all cards to display
//Realm realm = Realm.getDefaultInstance();

String urlToGet = "myurl";
String user_name = settings.getString("username", null);

OkHttpClient client = new OkHttpClient();

RequestBody formBody = new FormBody.Builder()
        .add("user_name", user_name)
        .build();

Request request = new Request.Builder()
        .url(urlToGet)
        .post(formBody)
        .build();

client.newCall(request).enqueue(new Callback() {
    @Override
    public void onFailure(Call call, IOException e) {
        e.printStackTrace();
    }

    @Override
    public void onResponse(Call call, final Response response) throws IOException {
        if (!response.isSuccessful()) {
            throw new IOException("Unexpected code " + response);
        }

        responseCardInInventory = response.body().string();

        handler.post(new Runnable() {
            @Override
            public void run() {

                List<CardInInv> cardListInInv = new ArrayList<>();

                Gson gson = new Gson();
                CardInInventory civ = gson.fromJson(responseCardInInventory, CardInInventory.class);
                cardListInInv = getCards(civ);

                //use realm to do all your card inventory stuff to get your resulting object
                dataCard = yourObjectListAfterUsingRealm;
                notifyDataSetChanged();
            }
        });
    }
});
}

Answer 2

移动此行 adapter = new inventoryFragmentRecyclerAdapter(context, yourList); 在onResponse()内，并在没有getCards();

的情况下直接传递列表

编辑：

在数据准备就绪时初始化适配器。在哪里？这是基于您的需求。

或使用空列表初始化它，并在更改内容（从列表中添加或删除或初始化全新列表）时调用adapter.notifyDataSetChanged()

Answer 3

使用空列表创建适配器
adapter = new inventoryFragmentRecyclerAdapter(this.getContext(), new ArrayList<Card>());

然后在你的适配器中创建一个这样的方法

public void updateCardList(List<Card> cardList) { this.mCards = cardList; notifyDataSetChanged(); }

并在中间调用此功能 @Override public void onResponse(Call call, final Response response)

onCreateView等待查询结果

3 个答案: