Question

通过Retrofit数据正常，我的自定义适配器（NewsAdapter，基于ArrayAdapter）之前已经填充，但我不得不对其进行一些调整而我不能让它一直在工作。

我们的想法是获取每个新闻源，获取每个特定新闻源的文章，然后使用这些文章填充我的GridView。根据我的理解，articles上的NewsAdapter成员被填充，但不是适配器本身。这是我用来检查值的代码和控制台输出：

控制台输出：

I/System.out: Source ID: nfl-news
I/System.out: Adapter count: 0
I/System.out: Response body: [pt.ismai.a26800.readr.Articles_Map@ca5fafc, pt.ismai.a26800.readr.Articles_Map@cd585, pt.ismai.a26800.readr.Articles_Map@8639fda, pt.ismai.a26800.readr.Articles_Map@9bbac0b, pt.ismai.a26800.readr.Articles_Map@ed5cae8, pt.ismai.a26800.readr.Articles_Map@c4a4501, pt.ismai.a26800.readr.Articles_Map@c6bdfa6, pt.ismai.a26800.readr.Articles_Map@876fde7, pt.ismai.a26800.readr.Articles_Map@3b0ad94, pt.ismai.a26800.readr.Articles_Map@b95303d]
I/System.out: Articles count: 10
I/System.out: Source ID: espn-cric-info
I/System.out: Adapter count: 0
I/System.out: Response body: [pt.ismai.a26800.readr.Articles_Map@f665032, pt.ismai.a26800.readr.Articles_Map@3ab9183, pt.ismai.a26800.readr.Articles_Map@4b50f00, pt.ismai.a26800.readr.Articles_Map@5a99339, pt.ismai.a26800.readr.Articles_Map@b253d7e, pt.ismai.a26800.readr.Articles_Map@50bc2df, pt.ismai.a26800.readr.Articles_Map@2dc1b2c]
I/System.out: Articles count: 17
I/System.out: Source ID: fox-sports
I/System.out: Adapter count: 0
I/System.out: Response body: [pt.ismai.a26800.readr.Articles_Map@80729f5, pt.ismai.a26800.readr.Articles_Map@253b38a, pt.ismai.a26800.readr.Articles_Map@513adfb, pt.ismai.a26800.readr.Articles_Map@385be18, pt.ismai.a26800.readr.Articles_Map@e6d7071]
I/System.out: Articles count: 22

ListNewsActivity ：

public class ListNewsActivity extends AppCompatActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        /* ... */

        // parameters for Sources endpoint
        String category = "sport";
        String language = "en";
        String country = "us";

        // Sources endpoint
        Sources_Interface client_sources = NewsAPI_Adapter.createService(Sources_Interface.class);
        Call<Sources_Map> call_sources = client_sources.getData(category, language, country);

        call_sources.enqueue(new Callback<Sources_Map>() {
            @Override
            public void onResponse(Call<Sources_Map> call_sources, Response<Sources_Map> response) {
                if (response.body() != null) {
                    final NewsAdapter nAdapter = new NewsAdapter(ListNewsActivity.this,
                            R.layout.article_layout);

                    for (final Sources_Content source : response.body().sources) {
                        if (source.sortBysAvailable.contains("latest")) {

                            // Articles endpoint
                            NewsAPI_Interface client = NewsAPI_Adapter.createService(NewsAPI_Interface.class);
                            Call<NewsAPI_Map> call = client.getData(source.id, "apiKeyHere");

                            call.enqueue(new Callback<NewsAPI_Map>() {
                                @Override
                                public void onResponse(Call<NewsAPI_Map> call, Response<NewsAPI_Map> response) {
                                    if (response.body() != null) {
                                        ExpandableHeightGridView gv_content = (ExpandableHeightGridView) findViewById(R.id.gv_content);
                                        nAdapter.addAll(response.body().articles);
                                        System.out.println("Source ID: " + source.id + "\n" +
                                                "Adapter count: " + nAdapter.getCount() + "\n" +
                                                "Response body: " + response.body().articles + "\n" +
                                                "Articles count: " + nAdapter.articles.size() + "\n");
                                        gv_content.setAdapter(nAdapter);
                                        gv_content.setExpanded(true);
                                    }
                                }

                                @Override
                                public void onFailure(Call<NewsAPI_Map> call, Throwable t) {
                                    System.out.println("An error ocurred!\n" +
                                            "URL: " + call.request().url() + "\n" +
                                            "Cause: " + t.getCause().toString());
                                }
                            });
                        }
                    }
                }
            }

            @Override
            public void onFailure(Call<Sources_Map> call_sources, Throwable t) {
                System.out.println("An error ocurred!");
            }
        });
    }
}

NewsAdapter ：

public class NewsAdapter extends ArrayAdapter<Articles_Map> {
    Context mContext;
    List<Articles_Map> articles;

    public NewsAdapter(Context c, int resource) {
        super(c, resource);
        this.mContext = c;
        this.articles = new ArrayList<>();
    }

    public NewsAdapter(Context c, int resource, List<Articles_Map> articles) {
        super(c, resource, articles);
        this.mContext = c;
        this.articles = articles;
    }

    public void addAll(List<Articles_Map> articles) {
        if (this.articles == null) {
            this.articles = new ArrayList<>(articles);
        } else {
            this.articles.addAll(articles);
        }
        notifyDataSetChanged();
    }

    @Override
    public View getView(int position, View convertView, ViewGroup parent) {
        // get the property we are displaying
        Articles_Map article = articles.get(position);

        // get the inflater and inflate the XML layout for each item
        LayoutInflater inflater = (LayoutInflater) mContext.getSystemService(Activity.LAYOUT_INFLATER_SERVICE);
        View view = inflater.inflate(R.layout.article_layout, null);

        ImageView thumbnail = (ImageView) view.findViewById(R.id.thumbnail);
        TextView title = (TextView) view.findViewById(R.id.title);
        TextView description = (TextView) view.findViewById(R.id.description);

        Picasso.with(mContext).load(article.urlToImage).into(thumbnail);
        title.setText(article.title);
        description.setText(article.description);

        return view;
    }
}

NewsAPI_Map ：

public class NewsAPI_Map {
    String status;
    String source;
    List<Articles_Map> articles;

    public NewsAPI_Map(String status, String source, List<Articles_Map> articles) {
        this.status = status;
        this.source = source;
        this.articles = articles;
    }
}

Articles_Map ：

public class Articles_Map {
    String title;
    String description;
    String url;
    String urlToImage;

    public Articles_Map(String title, String description, String url, String urlToImage) {
        this.title = title;
        this.description = description;
        this.url = url;
        this.urlToImage = urlToImage;
    }
}

Answer 1

尝试插入getCount()方法：

@Override
public int getCount(){
    int size = articles == null ? 0 : articles.size();
    return size;
}

Answer 2

关于getCount的东西返回0，因此适配器认为它不应该在列表中显示数据。我相信这是因为您调用的构造函数不会使用该类中的List数据列表初始化基础articles。

但是，您不需要在适配器实现中定义自己的List。 ArrayAdapter超级班有一个。

因此，删除这些引用。（由于getContext()可用，您也不需要上下文。）

public class NewsAdapter extends ArrayAdapter<Articles_Map> {
    Context mContext;

    public NewsAdapter(Context c, int resource) {
        super(c, resource);
        this.mContext = c;
    }

    public NewsAdapter(Context c, int resource, List<Articles_Map> articles) {
        super(c, resource, articles);
        this.mContext = c;
    }

然后，在getView中，使用getItem(position)代替。

@Override
public View getView(int position, View convertView, ViewGroup parent) {
    // get the property we are displaying
    Articles_Map article = getItem(position);

您仍然可以使用adapter.add或adapter.addAll，它会添加到基础List并通知数据集。

为什么我的自定义ArrayAdapter没有被填充？

2 个答案: