每 2 秒刷新一次从 JSON 响应中填充的 listView

Posted 2023-04-19

【中文标题】每 2 秒刷新一次从 JSON 响应中填充的 listView

【英文标题】：Refresh listView populated from JSON response every 2 seconds

【发布时间】：2019-05-31 18:16:44

【问题描述】：

我正在开发一个 android 应用程序，其中一个片段具有一个列表视图，该列表视图由来自 php 服务器的 JSON 响应填充。列表视图会根据需要显示，并且当前会在查看片段时更新。但是，这也是一个问题，因为列表仅在视图更改时才会更新，我希望 listView 每隔几毫秒清除和更新一次。

我的片段代码是：

public class eventFragment extends Fragment 
// TODO: Rename parameter arguments, choose names that match
// the fragment initialization parameters, e.g. ARG_ITEM_NUMBER
private static final String ARG_PARAM1 = "param1";
private static final String ARG_PARAM2 = "param2";

// TODO: Rename and change types of parameters
private String mParam1;
private String mParam2;

ListView eventView;
ArrayList<Events> eventList;
EventListAdapter adapter;
String streamName;
String applicationType = "live";
private static String value;

String url = "http://192.168.43.149/testing/eventStream.php";

private OnFragmentInteractionListener mListener;

public eventFragment() 
    // Required empty public constructor


/**
 * Use this factory method to create a new instance of
 * this fragment using the provided parameters.
 *
 * @param param1 Parameter 1.
 * @param param2 Parameter 2.
 * @return A new instance of fragment eventFragment.
 */
// TODO: Rename and change types and number of parameters
public static eventFragment newInstance(String param1, String param2) 
    eventFragment fragment = new eventFragment();
    Bundle args = new Bundle();
    args.putString(ARG_PARAM1, param1);
    args.putString(ARG_PARAM2, param2);
    fragment.setArguments(args);
    return fragment;


@Override
public void onCreate(Bundle savedInstanceState) 
    super.onCreate(savedInstanceState);
    if (getArguments() != null) 
        mParam1 = getArguments().getString(ARG_PARAM1);
        mParam2 = getArguments().getString(ARG_PARAM2);
    


@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
                         Bundle savedInstanceState) 
    // Inflate the layout for this fragment
    View view = inflater.inflate(R.layout.fragment_event, container, false);
    eventView = (ListView) view.findViewById(R.id.listView);
    eventList = new ArrayList<Events>();
    JSONObject streamInfo = new JSONObject();
    try 
        streamInfo.put("applicationType", applicationType);

        postJSONObject(url,streamInfo);


     catch (JSONException e) 
        // TODO Auto-generated catch block
        e.printStackTrace();
    


    return view;


// TODO: Rename method, update argument and hook method into UI event
public void onButtonPressed(Uri uri) 
    if (mListener != null) 
        mListener.onFragmentInteraction(uri);
    


@Override
public void onAttach(Context context) 
    super.onAttach(context);
    if (context instanceof OnFragmentInteractionListener) 
        mListener = (OnFragmentInteractionListener) context;
     else 
        throw new RuntimeException(context.toString()
                + " must implement OnFragmentInteractionListener");
    


@Override
public void onDetach() 
    super.onDetach();
    mListener = null;


/**
 * This interface must be implemented by activities that contain this
 * fragment to allow an interaction in this fragment to be communicated
 * to the activity and potentially other fragments contained in that
 * activity.
 * <p>
 * See the Android Training lesson <a href=
 * "http://developer.android.com/training/basics/fragments/communicating.html"
 * >Communicating with Other Fragments</a> for more information.
 */
public interface OnFragmentInteractionListener 
    // TODO: Update argument type and name
    void onFragmentInteraction(Uri uri);



public void postJSONObject(final String myurl, final JSONObject parameters) 

    class postJSONObject extends AsyncTask<Void, Void, String> 

        @Override
        protected void onPreExecute() 
            super.onPreExecute();
            //dialog[0] = new ProgressDialog(getActivity());
            //dialog[0].setMessage("Loading, please wait");
            //dialog[0].setTitle("Connecting server");
            //dialog[0].show();
            //dialog[0].setCancelable(false);
        


        @Override
        protected void onPostExecute(String s) 
            super.onPostExecute(s);

            try 
                //Toast.makeText(getContext().getApplicationContext(), s, Toast.LENGTH_LONG).show();
                loadIntoEventView(s);
             catch (Exception e) 
                e.printStackTrace();
            
        

        @Override
        protected String doInBackground(Void... voids) 

            HttpURLConnection conn = null;
            try 
                StringBuffer response = null;
                URL url = new URL(myurl);
                conn = (HttpURLConnection) url.openConnection();
                conn.setReadTimeout(10000);
                conn.setConnectTimeout(15000);
                conn.setRequestProperty("Content-Type", "application/json");
                conn.setDoOutput(true);
                conn.setRequestMethod("POST");
                OutputStream out = new BufferedOutputStream(conn.getOutputStream());
                BufferedWriter writer = new BufferedWriter(new OutputStreamWriter(out, "UTF-8"));
                writer.write(parameters.toString());
                writer.close();
                out.close();
                int responseCode = conn.getResponseCode();
                System.out.println("responseCode" + responseCode);
                switch (responseCode) 
                    case 200:
                        BufferedReader in = new BufferedReader(new InputStreamReader(conn.getInputStream()));
                        String inputLine;
                        response = new StringBuffer();
                        while ((inputLine = in.readLine()) != null) 
                            response.append(inputLine);
                        
                        in.close();
                        return response.toString();
                
             catch (IOException ex) 
                ex.printStackTrace();
             finally 
                if (conn != null) 
                    try 
                        conn.disconnect();
                     catch (Exception ex) 
                        ex.printStackTrace();
                    
                
            
            return null;

        
    

    postJSONObject postJSONObject = new postJSONObject();
    postJSONObject.execute();


private void loadIntoEventView(String json) throws JSONException 
    JSONArray jsonArray = new JSONArray(json);

    eventList.clear();
    final String[]  events = new String[jsonArray.length()];
    for (int i = 0; i < jsonArray.length(); i++) 
        JSONObject obj = jsonArray.getJSONObject(i);
        events[i] = obj.getString("title");

        Events video = new Events();

        video.setTitle(events[i]);
        //vidoe.setDescription(obj.getString("channelDescriptipn"));
        //channel.setDateCreated(obj.get("createdOn"));
        //vidoe.setImage(obj.getString("logoLocation"));

        eventList.add(video);
    
    //ArrayAdapter<String> arrayAdapter = new ArrayAdapter<String>(getActivity(), android.R.layout.simple_list_item_1);
    EventListAdapter adapter = new EventListAdapter(getActivity(), R.layout.eventparsedata, eventList);
    eventView.setAdapter(adapter);



    eventView.setOnItemClickListener(new AdapterView.OnItemClickListener() 

        @Override
        public void onItemClick(AdapterView<?> arg0, View arg1,
                                int position, long arg3) 

            streamName = Arrays.asList(events).get(position);
            Intent intent = new Intent(getActivity(), StreamPlayerActivity.class);
            intent.putExtra("videoname", streamName);
            startActivity(intent);

            System.out.println("arr: " + Arrays.asList(events).get(position));


        


    );

【参考方案1】：

如果您想每 x 秒执行一次操作，可以使用此代码（在此示例中，x 为 1000 毫秒 = 1 秒）

在您的片段类中定义它：

private Handler handler = new Handler();
Runnable updatePage = new Runnable() 
                @Override
                public void run() 

                    // do what you want in here (calling your web service request)                    


                    handler.postDelayed(updatePage,1000);
                
            ;

并像这样使用它（放在 onCreateView 方法中）：

handler.postDelayed(updatePage,1000);