ListView 不显示任何数据，getCount() returns 0，getView() 从不调用

Question

我正在尝试使用 AsyncTask 获取数据并显示到 ListView。它从不调用 getView()，我检查了 getCount() return 总是 0。

MainActivityFragment.java

public class MainActivityFragment extends Fragment {

    private final String LOG_TAG = MainActivityFragment.class.getSimpleName();

    SourceAdapter adapter;

    public MainActivityFragment() {
    }

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {
        View rootView = inflater.inflate(R.layout.fragment_main, container, false);
        adapter = new SourceAdapter(getActivity());

        ListView listView = (ListView) rootView.findViewById(R.id.listView);
        listView.setAdapter(adapter);
        Log.d(LOG_TAG,"after list view set to adapter");
        return rootView;
    }

    @Override
    public void onStart() {
        new FetchDataTask().execute();
        super.onStart();
    }

    public class FetchDataTask extends AsyncTask<String, Void, SourceObject[]>{

        private final String LOG_TAG = FetchDataTask.class.getSimpleName();

        private SourceObject[] getSourceDataFromJson(String jsonStr)throws JSONException{

            JSONArray jsonArray = new JSONArray(jsonStr);
            SourceObject[] sourceObjects = new SourceObject[jsonArray.length()];

            for (int i=0; i<jsonArray.length();i++){
                sourceObjects[i] = new SourceObject(
                        jsonArray.getJSONObject(i).getJSONObject("commit").getJSONObject("author").getString("name"),
                        jsonArray.getJSONObject(i).getJSONObject("commit").getJSONObject("author").getString("name"),
                        jsonArray.getJSONObject(i).getJSONObject("commit").getString("message")
                );
            }
            return sourceObjects;
        }

        @Override
        protected SourceObject[] doInBackground(String... params) {

            HttpURLConnection urlConnection = null;
            BufferedReader reader = null;
            String jsonStr = null;

            try {
                String baseUrl = "https://api.github.com/repos/rails/rails/commits";

                URL url = new URL(baseUrl);
                Log.d(LOG_TAG,"URL IS "+url);

                urlConnection = (HttpURLConnection) url.openConnection();
                urlConnection.setRequestMethod("GET");
                urlConnection.connect();

                InputStream inputStream = urlConnection.getInputStream();
                StringBuffer buffer = new StringBuffer();

                if (inputStream == null)
                    return null;

                reader = new BufferedReader(new InputStreamReader(inputStream));
                String line;
                while ((line = reader.readLine()) != null){
                    buffer.append(line + "\n");
                }

                if (buffer.length() == 0) {
                    return null;
                }

                jsonStr = buffer.toString();
                Log.d(LOG_TAG,"JSON STRING "+jsonStr);
            }catch (IOException e){
                Log.e(LOG_TAG, "ERROR"+e);
                return null;
            }finally {
                if (urlConnection != null) {
                    urlConnection.disconnect();
                }
                if (reader != null) {
                    try {
                        reader.close();
                    } catch (final IOException e) {
                        Log.e(LOG_TAG, "Error closing stream", e);
                    }
                }
            }
            try {
                return getSourceDataFromJson(jsonStr);
            } catch (JSONException e) {
                Log.e(LOG_TAG, e.getMessage(), e);
                e.printStackTrace();
            }
            return null;
        }

        @Override
        protected void onPostExecute(SourceObject[] strings) {

            adapter.notifyDataSetChanged();
            super.onPostExecute(strings);
        }
    }
}

SourceAdapter.java

public class SourceAdapter extends BaseAdapter {
    private final String LOG_TAG = SourceAdapter.class.getSimpleName();

    Context context;
    ArrayList<SourceObject> objects = new ArrayList<SourceObject>();

    public SourceAdapter(Context context) {
        this.context = context;
    }

    @Override
    public int getCount() {
        Log.d(LOG_TAG,"getCount called "+objects.size());
        return objects.size();
    }

    @Override
    public Object getItem(int position) {
        Log.d(LOG_TAG,"getItem called");
        return objects.get(position);
    }

    @Override
    public long getItemId(int position) {
        return 0;
    }

    @Override
    public View getView(int position, View convertView, ViewGroup parent) {
        Log.d(LOG_TAG,"get view method is called");
        SourceObject sourceObject = (SourceObject) getItem(position);

        if (convertView == null){
            LayoutInflater inflater = (LayoutInflater) context
                    .getSystemService(Context.LAYOUT_INFLATER_SERVICE);
            convertView = inflater.inflate(R.layout.list_item_source,parent,false);
        }

        TextView personName = (TextView) convertView.findViewById(R.id.person_name);
        TextView commit = (TextView) convertView.findViewById(R.id.xxx);
        TextView commitMessage = (TextView) convertView.findViewById(R.id.commit_message);

        personName.setText(sourceObject.getPersonName());
        commit.setText(sourceObject.getCommit());
        commitMessage.setText(sourceObject.getCommitMessage());

        return convertView;
    }
}

请帮忙。

Answer 1

您没有将从 AsyncTask 检索到的数据设置到适配器。

将此方法添加到您的适配器中 class:

public void setItems(SourceObject[] items) {
    this.objects = new ArrayList<SourceObject>();
    for(SourceObject item : items){
        this.objects.add(item);
    }
    this.notifyDataSetChanged();
}

并将 AsyncTask 的 onPostExecute 更改为：

@Override
protected void onPostExecute(SourceObject[] strings) {
    adapter.setItems(strings);
    super.onPostExecute(strings);
}

ListView 不显示任何数据，getCount() returns 0，getView() 从不调用

ListView does not show any data, getCount() returns 0, getView() never calls

android

baseadapter