异步任务片段背景数据

Question

我对如何从这个网站将大量模板JSON数据加载到我的应用程序中而不减慢主UI线程感到非常陌生和困惑。我可以将要从JSON响应加载的数据加载到我的recycler视图中，但单击底部显示该数据的导航选项卡需要很长时间才能加载到页面上。

我明白这是因为数据没有正确加载到后台线程，这就是我感到困惑的地方。

我希望能够从后台任务返回一个ArrayList，并将填充的ArrayList作为我的recyclerview适配器传递给我。以下是包含AsyncTask和recyclerview代码的片段：

public class LoadJSONAsyncTask extends AsyncTask<String, String, ArrayList<String>>
    {

        protected void onPreExecute()
        {


        }

        public String getJSONFromURL(String inUrl) throws IOException
        {
            URL url2 = new URL(inUrl);
            HttpURLConnection urlConnection = (HttpURLConnection) url2.openConnection();
            StringBuilder total = new StringBuilder();

            try
            {
                InputStream in = new BufferedInputStream(urlConnection.getInputStream());
                BufferedReader r = new BufferedReader(new InputStreamReader(in));

                for(String line; (line = r.readLine()) != null;)
                {
                    total.append(line).append('\n');
                }
            }
            catch(Exception e)
            {
                e.printStackTrace();
            }

            finally
            {
                urlConnection.disconnect();
            }

            return total.toString();
        }

        @Override
        protected ArrayList<String> doInBackground(String... params)
        {
            LoadJSONAsyncTask jParser = new LoadJSONAsyncTask();
            JSONArray array = null;
            JSONObject json = null;
            String url = "https://baconipsum.com/api/?type=meat-and-filler";

            StringBuilder returnMe = new StringBuilder();
            results = new ArrayList<>();

            try {
                array = new JSONArray(jParser.getJSONFromURL(url));
                for(int n = 0; n < array.length(); n++)
                {
                    try {
                        json = new JSONObject();

                        json.put("name", jParser.getJSONFromURL(url));
                        results.add(jParser.getJSONFromURL(url));
                    } catch (Exception e) {
                        e.printStackTrace();
                    }
                }

            } catch (JSONException e) {
                e.printStackTrace();
            } catch (IOException e) {
                e.printStackTrace();
            }



            return results;
        }

        protected void onPostExecute()
        {

        }

    }

在我的片段中的onCreateView（）方法中，recyclerview的定义如下：

@Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {
        // Inflate the layout for this fragment
        try
        {
            results = new LoadJSONAsyncTask().execute(url).get();
            for(int i = 0; i < results.size(); i++)
            {
                newsFeedList.add(new NewsFeed(results.get(i)));
            }
        } catch (ExecutionException e) {

        } catch (InterruptedException e) {e.printStackTrace();
            e.printStackTrace();
        }
        View view = inflater.inflate(R.layout.fragment_feeds, container, false);

        newsFeedList = new ArrayList<>();

        recyclerView = (RecyclerView) view.findViewById(R.id.recyclerView);
        recyclerView.setHasFixedSize(true);
        recyclerView.setLayoutManager(new LinearLayoutManager(getActivity()));


        final NewsAdapter mAdapter = new NewsAdapter(getActivity(), newsFeedList);
        recyclerView.setAdapter(mAdapter);


        return view;
    }

我觉得在onCreateView（）方法中，调用arraylist来执行数据的方式就是挂起线程上的数据。一个清晰的解释和例子将不胜感激！

Answer 1

在LoadJSONAsync任务结束后调用片段

Answer 2

覆盖LoadJSONAsyncTask的onPostExecute，并将所有UI更新放在那里。

@Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {
        // Inflate the layout for this fragment

        View view = inflater.inflate(R.layout.fragment_feeds, container, false);

        newsFeedList = new ArrayList<>();

        recyclerView = (RecyclerView) view.findViewById(R.id.recyclerView);
        recyclerView.setHasFixedSize(true);
        recyclerView.setLayoutManager(new LinearLayoutManager(getActivity()));

        final NewsAdapter mAdapter = new NewsAdapter(getActivity(), newsFeedList);
        recyclerView.setAdapter(mAdapter);

        LoadJSONAsyncTask asyncTask = new LoadJSONAsyncTask() {
        @Override
        void onPostExecute(ArrayList<String> results) {
                // update your adapter here with the result

                for(int i = 0; i < results.size(); i++)
                {
                    newsFeedList.add(new NewsFeed(results.get(i)));
                }

                // notify adapter here to update the view
                mAdapter.notifyDataSetChanged()
            }
        }

        asyncTask.execute(url);

        return view;
    }

。get（）挂起主线程。

下面是如何正确使用异步任务。https://developer.android.com/reference/android/os/AsyncTask