来自 JSON 的 RecyclerView 从 API 获取数组

Question

我无法将一些从 API 获取到 RecyclerView 的数据显示到选项卡式 Activity 片段中。首先有一个错误：

E/RecyclerView﹕ No adapter attached; skipping layout

这是我的代码，类和布局：

这是片段 RegPicsFragment：

public class RegPicsFragment extends Fragment {

ProgressBar progressBar;
View view;

RecyclerView myRecyclerView;
RecyclerView.LayoutManager myLayoutManager;
RecyclerView.Adapter myAdapter;

List<RegEndaneredItem> myItems;

@Nullable
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
    view = inflater.inflate(R.layout.frag_regpics, container ,false);

    return view;

}


@Override
public void onActivityCreated(@Nullable Bundle savedInstanceState) {
    super.onActivityCreated(savedInstanceState);

    FontChangeCrawler fontChanger = new FontChangeCrawler(getActivity().getAssets(), "iransans.ttf");
    fontChanger.replaceFonts((ViewGroup) this.getView());

    progressBar = (ProgressBar) view.findViewById(R.id.progressBar);

    myRecyclerView = (RecyclerView) view.findViewById(R.id.recycler_view2);
    myRecyclerView.setLayoutManager(new LinearLayoutManager(getActivity()));

    myLayoutManager = new GridLayoutManager(view.getContext(), 1);
    myRecyclerView.setLayoutManager(myLayoutManager);

}

class RetrieveFeedTask extends AsyncTask<Void, Void, String> {

    private Exception exception;

    protected void onPreExecute() {
        progressBar.setVisibility(View.VISIBLE);
    }

    protected String doInBackground(Void... urls) {

        try {
            URL url = new URL("http://jsonplaceholder.typicode.com/users");
            HttpURLConnection urlConnection = (HttpURLConnection) url.openConnection();
            try {
                BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(urlConnection.getInputStream()));
                StringBuilder stringBuilder = new StringBuilder();
                String line;
                while ((line = bufferedReader.readLine()) != null) {
                    stringBuilder.append(line).append("\n");
                }
                bufferedReader.close();
                return stringBuilder.toString();
            }
            finally{
                urlConnection.disconnect();
            }
        }
        catch(Exception e) {
            Log.e("ERROR", e.getMessage(), e);
            return null;
        }
    }

    protected void onPostExecute(String response) {
        if(response == null) {
            response = "THERE WAS AN ERROR";
        }


        progressBar.setVisibility(View.GONE);

            try {
                JSONArray data = new JSONArray(response);
                for(int i=0; i< data.length(); i++) {
                    String name = data.getJSONObject(i).getString("name");
                    Log.i("milad", name);

                    myItems.add((RegEndaneredItem) myItems);
                }
            } catch (JSONException e) {
                e.printStackTrace();
            }

        myAdapter = new RegGridAdapter(myItems);
        myRecyclerView.setAdapter(myAdapter);
    }
}

这是适配器 RegGridAdapter：

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

List<RegEndaneredItem> myItems;

public RegGridAdapter(List<RegEndaneredItem> myItems) {
    this.myItems = myItems;
}

@Override
public ViewHolder onCreateViewHolder(ViewGroup viewGroup, int i) {
    View v = LayoutInflater.from(viewGroup.getContext())
            .inflate(R.layout.reg_grid_item, viewGroup, false);
    ViewHolder viewHolder = new ViewHolder(v);
    return viewHolder;
}

@Override
public void onBindViewHolder(ViewHolder viewHolder, int i) {
    RegEndaneredItem nature = myItems.get(i);
    viewHolder.tvspecies.setText(nature.getName());
}

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

class ViewHolder extends RecyclerView.ViewHolder{

    public TextView tvspecies;

    public ViewHolder(View itemView) {
        super(itemView);
        tvspecies = (TextView)itemView.findViewById(R.id.tv_species);

        FontChangeCrawler fontChanger = new FontChangeCrawler(itemView.getContext().getAssets(), "iransans.ttf");
        fontChanger.replaceFonts((ViewGroup) itemView);
    }


}

这是 Getter 和 Setter RegEndaneredItem:

public class RegEndaneredItem {

private String mName;

public String getName() {
    return mName;
}

public void setName(String name) {
    this.mName = name;
}

最后是布局 frag_regpics：

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical">

<android.support.v7.widget.RecyclerView
    android:id="@+id/recycler_view2"
    android:layout_width="match_parent"
    android:layout_height="match_parent"/>

<ProgressBar
    android:id="@+id/progressBar"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:indeterminate="true"
    android:layout_centerHorizontal="true"
    android:visibility="gone" />

</LinearLayout>

Answer 1

在 onActivityCreated 中设置一个带有空列表的适配器。

List<RegEndaneredItem> myItems = new ArrayList<RegEndaneredItem>();
myAdapter = new RegGridAdapter(myItems);
myRecyclerView.setAdapter(myAdapter);

还要检查 RegPicsFragment 中的 myItems 列表是否为空。

我没有看到你对 myItems 的初始化。

编辑

 myItems.add((RegEndaneredItem) myItems);

这一行没有任何意义。您必须为 RegEndaneredItem 的对象设置值并将其添加到列表中。

RegEndaneredItem reg = new RegEndaneredItem();
reg.setName(name);//calling Your SetterMethod
myItems.add(reg);

Answer 2

也许我的回答有点跑题了，但是如果你想降低代码的复杂性，你可以改用这个库Android RESTAdapter

实施起来真的很简单，而且每次都很有魅力。

来自 JSON 的 RecyclerView 从 API 获取数组

RecyclerView from JSON Array fetched from API

java

android

json

android-fragments

android-recyclerview

编辑