应用程序在模拟器上显示空白屏幕

Question

我正在开发体育新闻安卓应用，但是当我运行应用时它显示白屏screenshot of emulator。

在我的适配器类下面

公共类 ArticleAdapter 扩展 RecyclerView.Adapter {

private List<Article> articles;

public ArticleAdapter(List<Article> articles, SportNews sportNews) {
    this.articles = articles;

}

@NonNull
@Override
public CustomViewHolder onCreateViewHolder(@NonNull ViewGroup viewGroup, int i) {
    View itemView = (View) LayoutInflater.from(viewGroup.getContext()).inflate(R.layout.article_list, null);
    return new CustomViewHolder(itemView);
}

@Override
public void onBindViewHolder(@NonNull CustomViewHolder customViewHolder, int position) {
    Article article = articles.get(position);
    customViewHolder.articleAuthor.setText(article.getAuthor());
    customViewHolder.articleTitle.setText(article.getTitle());
    Picasso.get().load(article.getUrlToImage()).into(customViewHolder.articleImage);

}


@Override
public int getItemCount() {
    if(articles == null) return 0;
    return articles.size();
}

public class CustomViewHolder extends RecyclerView.ViewHolder {
    @BindView(R.id.articleAuthor)
    TextView articleAuthor;
    @BindView(R.id.articleTitle)
    TextView articleTitle;
    @BindView(R.id.articleImage)
    ImageView articleImage;


    public CustomViewHolder(View view) {
        super(view);
        ButterKnife.bind(this, view);


    }
}

}

下面的改造接口类 公共接口 SportInterface {

@GET("/v2/top-headlines?sources=bbc-sport&apiKey=d03441ae1be44f9cad8c38a2fa6db215")
Call<SportNews> getArticles();

}

改造客户端下方

公共类 SportClient {

private static final String ROOT_URL = "https://newsapi.org";

/**
 * Get Retrofit Instance
 */
private static Retrofit getRetrofitInstance() {
    return new Retrofit.Builder()
            .baseUrl(ROOT_URL)
            .addConverterFactory(GsonConverterFactory.create())
            .build();
}

/**
 * Get API Service
 *
 * @return API Service
 */
public static SportInterface getApiService() {
    return getRetrofitInstance().create(SportInterface.class);
}

}

在 MainActivity.java 下

公共类 MainActivity 扩展 AppCompatActivity {

private SportNews sportNews;
private List<Article> articleList;

private ArticleAdapter articleAdapter;
@BindView(R.id.recyclerView)
RecyclerView recyclerView;

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

    SportInterface sportInterface = SportClient.getApiService();
    Call<SportNews> call = sportInterface.getArticles();
    call.enqueue(new Callback<SportNews>() {
        @Override
        public void onResponse(Call<SportNews> call, Response<SportNews> response) {
            sportNews =  response.body();
            articleAdapter = new ArticleAdapter( articleList, sportNews);
            RecyclerView.LayoutManager layoutManager = new LinearLayoutManager(getApplicationContext());
            recyclerView.setLayoutManager(layoutManager);
            recyclerView.setAdapter(articleAdapter);
        }

        @Override
        public void onFailure(Call<SportNews> call, Throwable t) {

        }
    });


}

}

低于 Model SportNews 类

公开课体育新闻{

@SerializedName("status")
@Expose
private String status;
@SerializedName("totalResults")
@Expose
private Integer totalResults;
@SerializedName("articles")
@Expose
private List<Article> articles = null;

public String getStatus() {
    return status;
}

public void setStatus(String status) {
    this.status = status;
}

public Integer getTotalResults() {
    return totalResults;
}

public void setTotalResults(Integer totalResults) {
    this.totalResults = totalResults;
}

public List<Article> getArticles() {
    return articles;
}

public void setArticles(List<Article> articles) {
    this.articles = articles;
}

}

下面的json响应

{
    "status": "ok",
    "totalResults": 10,
    "articles": [
        {
            "source": {
                "id": "bbc-sport",
                "name": "BBC Sport"
            },
            "author": "BBC Sport",
            "title": "Gordon Taylor: PFA chief executive set to step down after 38 years",
            "description": "Gordon Taylor to announce he will step down as chief executive of the Professional Footballers' Association (PFA) at the end of the season after 38 years.",
            "url": "http://www.bbc.co.uk/sport/football/47691299",
            "urlToImage": "https://ichef.bbci.co.uk/onesport/cps/624/cpsprodpb/13590/production/_97584297_breaking_news.png",
            "publishedAt": "2019-03-27T13:04:18Z",
            "content": "Gordon Taylor is set to announce he is standing down as chief executive of the Professional Footballers' Association after 38 years in the role.\r\nIt follows a mutiny from PFA chairman Ben Purkiss and former players over governance issues and controversy over … [+675 chars]"
        },
 ]
}

Answer 1

您好，只需复制粘贴下面的代码，因为我已经编辑了您的 MainActivity 类，您忘记添加来自 sportNews 对象的列表，您可以访问该列表以响应 api 调用。

public class MainActivity extends AppCompatActivity {

private SportNews sportNews;
private List<Article> articleList = new ArrayList<Article>();

private ArticleAdapter articleAdapter;
@BindView(R.id.recyclerView)
RecyclerView recyclerView;

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

    SportInterface sportInterface = SportClient.getApiService();
    Call<SportNews> call = sportInterface.getArticles();
    call.enqueue(new Callback<SportNews>() {
        @Override
        public void onResponse(Call<SportNews> call, Response<SportNews> response) {
            sportNews =  response.body();
            if(sportNews != null && sportNews.getArticles() != null){
                articleList.addAll(sportNews.getArticles());
            }
            articleAdapter = new ArticleAdapter( articleList, sportNews);
            RecyclerView.LayoutManager layoutManager = new LinearLayoutManager(getApplicationContext());
            recyclerView.setLayoutManager(layoutManager);
            recyclerView.setAdapter(articleAdapter);
        }

        @Override
        public void onFailure(Call<SportNews> call, Throwable t) {

        }
    });

}
}

Answer 2

你的问题出在那一行

            articleAdapter = new ArticleAdapter( articleList, sportNews);

应该换成这个

articleList=sportNews.getArticles();
articleAdapter = new ArticleAdapter( articleList, sportNews);

Answer 3

试试这个。我认为你的适配器是错误的。

public class ArticleAdapter extends RecyclerView.Adapter<ArticleAdapter.CustomViewHolder> {