java - 针对特定位置的recyclerview setadapter

Question

我使用Recycleview创建了一个“水平 ListView ”。

由于我的程序中有 async 任务，我无法从 fetchbook 类检索图书结果，因此我需要在类内设置适配器。

我的代码如下所示:

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


    ArrayList<String> names = new ArrayList<>();
    names.add("szF_pLGmJTQC");
    names.add("QTKD3-mMZFYC");

    for (int i = 0; i<names.size(); i++){
        fetchBooks(names.get( i ));

    }

}


private void fetchBooks(String query) {

    client = new MyBookClient();
    final ArrayList<String> authors = new ArrayList<>(  );
    final ArrayList<String> titles = new ArrayList<>(  );
    final ArrayList<String> image = new ArrayList<>(  );
    MyBook books = new MyBook();
    client.getBooks( query, new JsonHttpResponseHandler(){
        @Override
        public void onSuccess(int statusCode, Header[] headers, JSONObject response){
            if(response!=null){
                MyBook books = MyBook.fromJson(response);

                authors.add(books.getAuthor());
                titles.add(books.getTitle());
                image.add(books.getCoverUrl());

                RecyclerView recyclerView = findViewById(R.id.rvAnimals);
                LinearLayoutManager horizontalLayoutManager
                        = new LinearLayoutManager(MainActivity.this, LinearLayoutManager.HORIZONTAL, false);
                recyclerView.setLayoutManager(horizontalLayoutManager);
                adapter = new MyRecyclerViewAdapter(MainActivity.this, authors, titles,image);
                adapter.setClickListener(MainActivity.this);
                recyclerView.setAdapter(adapter);

                Toast.makeText(MainActivity.this, "You clicked " + books.getAuthor(), Toast.LENGTH_SHORT).show();
            }
        }
    });
}

但是，它会导致适配器清理先前的 View 并添加当前的 View 。

适配器的代码添加如下:

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

    private List<String> mViewAuthor;
    private List<String> mTitles;
    private List<String> mimages;
    private LayoutInflater mInflater;
    private ItemClickListener mClickListener;
    private Context mContext;

    MyRecyclerViewAdapter(Context context, List<String> authors, List<String> titles, List<String> image) {
        this.mInflater = LayoutInflater.from(context);
        this.mViewAuthor = authors;
        this.mTitles = titles;
        this.mimages = image;
        this.mContext = context;
    }

    @Override
    @NonNull
    public ViewHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
        View view = mInflater.inflate( R.layout.recyclerview_item, parent, false);
        return new ViewHolder(view);
    }

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

        String color = mViewAuthor.get(position);
        String animal = mTitles.get(position);
        String image = mimages.get( position);
        holder.tvAuthor.setText(color);
        holder.tvTitle.setText(animal);

        Picasso.with(mContext).load(Uri.parse(image)).error(R.drawable.ic_nocover).into(holder.ivBookCover);
    }

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

public class ViewHolder extends RecyclerView.ViewHolder implements View.OnClickListener {
        TextView tvAuthor;
        TextView tvTitle;
        ImageView ivBookCover;

        ViewHolder(View itemView) {
            super(itemView);
            tvAuthor = itemView.findViewById(R.id.tvAuthor);
            tvTitle = itemView.findViewById(R.id.tvTitle);
            ivBookCover = itemView.findViewById(R.id.ivBookCover);
            itemView.setOnClickListener(this);
        }

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

    public String getItem(int id) {
        return mViewAuthor.get(id);
    }

    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);
    }

}

MyBook的代码是:

public class MyBook implements Serializable {
    private String author;
    private String title;
    private String bookid;
    private String rating;

    public String getTitle() {
        return title;
    }

    public String getAuthor() {
        return author;
    }

    public String getId() {
        return bookid;
    }

    public String getRating(){
        return rating;
    }


    public static MyBook fromJson(JSONObject jsonObject) {
        MyBook book = new MyBook();
        try {

            JSONObject volumeInfo = jsonObject.getJSONObject( "volumeInfo" );
            book.title = volumeInfo.has("title") ? volumeInfo.getString("title") : "";
            book.author = getAuthor(volumeInfo);
            book.bookid = jsonObject.has("id") ? jsonObject.getString("id") : "";
            book.rating = volumeInfo.has("averageRating") ? String.valueOf(volumeInfo.getDouble("averageRating")) : "0";
        } catch (JSONException e) {
            e.printStackTrace();
            return null;
        }
        return book;
    }

    private static String getAuthor(final JSONObject jsonObject) {
        try {
            final JSONArray authors = jsonObject.getJSONArray("authors");
            int numAuthors = authors.length();
            final String[] authorStrings = new String[numAuthors];
            for (int i = 0; i < numAuthors; ++i) {
                authorStrings[i] = authors.getString(i);
            }
            return TextUtils.join(", ", authorStrings);
        } catch (JSONException e) {
            return "";
        }
    }

}

有什么方法可以调用setadapter，同时定义我想要添加 View 的位置吗？

类似于:

fetchBooks(names.get( i ), i);

其中第二个参数i是适配器内的位置，因此我可以在位置i=0处获得第一个结果，然后在i=1处获得第二个结果。

或者有没有一种方法可以从 fetchBooks 类返回书籍？

谢谢

Answer 1

However, it causes the adapter to clean the previous view and add on it the current.

据我所知，您正在尝试将查询结果添加到 RecyclerView 列表中，但问题是它在添加新查询结果时从列表中删除了旧/上一个查询结果。并且您需要保留所有结果。如有错误请指正。

此行为可能是由于每次在 onSucess() 方法内获得新的查询结果时实例化新适配器所致。所以你可以通过将这部分代码转移到onCreate()方法来避免这种情况；然后，对于每个 onSuccess() 调用，您只需调用 adapter.notifyDataSetChanged() 即可通知适配器其数据源已更改，因此请自行更新。

这也要求我们不要用新数据实例化适配器，而只需向适配器添加新方法，以使用 .addAll() 方法更新列表。

所以改变:

MyRecyclerViewAdapter adapter;

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

    ArrayList<String> names = new ArrayList<>();
    names.add("szF_pLGmJTQC");
    names.add("QTKD3-mMZFYC");

    RecyclerView recyclerView = findViewById(R.id.rvAnimals);
    LinearLayoutManager horizontalLayoutManager
            = new LinearLayoutManager(MainActivity.this, LinearLayoutManager.HORIZONTAL, false);
    recyclerView.setLayoutManager(horizontalLayoutManager);
    adapter = new MyRecyclerViewAdapter(MainActivity.this, new ArrayList<>(), new ArrayList<>(), new ArrayList<>());
    adapter.setClickListener(MainActivity.this);
    recyclerView.setAdapter(adapter);


    for (int i = 0; i<names.size(); i++){
        fetchBooks(names.get( i ));
    }

}


private void fetchBooks(String query) {

    client = new MyBookClient();
    MyBook books = new MyBook();
    client.getBooks( query, new JsonHttpResponseHandler(){
        @Override
        public void onSuccess(int statusCode, Header[] headers, JSONObject response){
            if(response!=null){
                MyBook books = MyBook.fromJson(response);

                adapter.addBooks(books.getAuthor(), books.getTitle(), books.getCoverUrl());

                Toast.makeText(MainActivity.this, "You clicked " + books.getAuthor(), Toast.LENGTH_SHORT).show();
            }
        }
    });
}

并将以下方法添加到适配器代码

public void addBook(String author, String title, String image) {
    this.mViewAuthor.add(author);
    this.mTitles.add(title);
    this.mimages.add(image);
    this.notifyDataSetChanged();
}

如果您需要进一步的帮助，我随时欢迎