Populate Listview from JSON

Question

有人知道动态加载Json的例子吗数据到ListView中，我看到的大多数示例都只使用某种类型的静态数组。我需要装载10行Json数据，然后在底部有一个负载更多。。获得接下来的10个等等。请举例使用Json。。。。

Answer 1

程序员Bruce是正确的，没有默认的方法。然而，有一种非常干净和简单的方法可以实现这一点。这是我用来处理JSONArray的适配器。

class JSONAdapter extends BaseAdapter implements ListAdapter {
    private final Activity activity;
    private final JSONArray jsonArray;
    private JSONAdapter(Activity activity, JSONArray jsonArray) {
        assert activity != null;
        assert jsonArray != null;
        this.jsonArray = jsonArray;
        this.activity = activity;
    }

    @Override public int getCount() {
        return jsonArray.length();
    }
    @Override public JSONObject getItem(int position) {
        return jsonArray.optJSONObject(position);
    }
    @Override public long getItemId(int position) {
        JSONObject jsonObject = getItem(position);
        return jsonObject.optLong("id");
    }
    @Override public View getView(int position, View convertView, ViewGroup parent) {
        if (convertView == null)
            convertView = activity.getLayoutInflater().inflate(R.layout.row, null);
        JSONObject jsonObject = getItem(position);  
        return convertView;
    }
}

Answer 2

Android没有现成的适配器来用JSON数组填充ListView，就像用数据库记录填充ListView一样。

我建议您使用JSON数据填充您选择的Java数据结构，并使用ListViews，使用不同的自定义行从不同的集合填充它们。

下面是一个从JSON数组填充List，然后使用List填充ListView的简单示例。

import java.util.ArrayList;
import java.util.List;
import org.json.JSONArray;
import android.app.Activity;
import android.os.Bundle;
import android.widget.ArrayAdapter;
import android.widget.ListView;
public class Main extends Activity
{
  @Override
  public void onCreate(Bundle savedInstanceState)
  {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.main);
    try
    {
      String jsonInput = "["one","two","three","four","five","six","seven","eight","nine","ten"]";
      JSONArray jsonArray = new JSONArray(jsonInput);
      int length = jsonArray.length();
      List<String> listContents = new ArrayList<String>(length);
      for (int i = 0; i < length; i++)
      {
        listContents.add(jsonArray.getString(i));
      }
      ListView myListView = (ListView) findViewById(R.id.my_list);
      myListView.setAdapter(new ArrayAdapter<String>(this, android.R.layout.simple_list_item_1, listContents));
    }
    catch (Exception e)
    {
      // this is just an example
    }
  }
}

Answer 3

dbaugh有一个很好的答案，但这篇文章解释了如何为我们这些不知道该何去何从的人使用它。

Answer 4

尝试以下操作：

JSON解析程序类：

public class JSONParser {
    static InputStream is = null;
    static JSONObject jObj = null;
    static String json = "";
    // constructor
    public JSONParser() {
    }
    // function get json from url
    // by making HTTP POST or GET mehtod
    public JSONObject makeHttpRequest(String url, String method,
            List<NameValuePair> params) {
        // Making HTTP request
        try {
            // check for request method
            if (method == "POST") {
                // request method is POST
                // defaultHttpClient
                DefaultHttpClient httpClient = new DefaultHttpClient();
                HttpPost httpPost = new HttpPost(url);
                httpPost.setEntity(new UrlEncodedFormEntity(params));
                HttpResponse httpResponse = httpClient.execute(httpPost);
                HttpEntity httpEntity = httpResponse.getEntity();
                is = httpEntity.getContent();
            } else if (method == "GET") {
                // request method is GET
                DefaultHttpClient httpClient = new DefaultHttpClient();
                String paramString = URLEncodedUtils.format(params, "utf-8");
                url += "?" + paramString;
                HttpGet httpGet = new HttpGet(url);
                HttpResponse httpResponse = httpClient.execute(httpGet);
                HttpEntity httpEntity = httpResponse.getEntity();
                is = httpEntity.getContent();
            }
        } catch (UnsupportedEncodingException e) {
            e.printStackTrace();
        } catch (ClientProtocolException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }
        try {
            BufferedReader reader = new BufferedReader(new InputStreamReader(
                    is, "iso-8859-1"), 8);
            StringBuilder sb = new StringBuilder();
            String line = null;
            while ((line = reader.readLine()) != null) {
                sb.append(line + "n");
            }
            is.close();
            json = sb.toString();
        } catch (Exception e) {
            Log.e("Buffer Error", "Error converting result " + e.toString());
        }
        // try parse the string to a JSON object
        try {
            jObj = new JSONObject(json);
        } catch (JSONException e) {
            Log.e("JSON Parser", "Error parsing data " + e.toString());
        }
        // return JSON String
        return jObj;
    }
}

显示Listview:的片段类

public static class EventFragment extends ListFragment {
        ArrayList<HashMap<String, String>> eventsList;
        private String url_all_events = //url goes here;
        private ProgressDialog pDialog;
        JSONParser jParser = new JSONParser();
        // JSON Node names
        private static final String CONNECTION_STATUS = "success";
        private static final String TABLE_EVENT = "Event";
        private static final String pid = "pid";
        private static final String COL_GROUP = "Group";
        private static final String COL_NAME = "Event_Name";
        private static final String COL_DESC = "Event_Desc";
        private static final String COL_DATE = "Event_Date";
        private static final String COL_TIME = "Event_Time";
        JSONArray Events = null;
        public static final String ARG_SECTION_NUMBER = "section_number";
        public EventFragment() {
        }
        public void onStart() {
            super.onStart();
            eventsList = new ArrayList<HashMap<String, String>>();
            new LoadAllEvents().execute();
            // selecting single ListView item
            ListView lv = getListView();
            // Lauching the Event details screen on selecting a single event
            lv.setOnItemClickListener(new OnItemClickListener() {
                @Override
                public void onItemClick(AdapterView<?> parent, View view,
                        int position, long id) {
                    // getting values from selected ListItem
                    String ID = ((TextView) view.findViewById(R.id.pid))
                            .getText().toString();
                    Intent intent = new Intent(view.getContext(),
                            EventDetails.class);
                    intent.putExtra(pid, ID);
                    view.getContext().startActivity(intent);
                }
            });
        }
        public View onCreateView(LayoutInflater inflater, ViewGroup container,
                Bundle savedInstanceState) {
            View rootView = inflater.inflate(R.layout.fragment_events,
                    container, false);
            return rootView;
        }
        class LoadAllEvents extends AsyncTask<String, String, String> {
            /**
             * Before starting background thread Show Progress Dialog
             * */
            @Override
            protected void onPreExecute() {
                super.onPreExecute();
                pDialog = new ProgressDialog(getActivity());
                pDialog.setMessage("Just a moment...");
                pDialog.setIndeterminate(true);
                pDialog.setCancelable(true);
                pDialog.show();
            }
            protected String doInBackground(String... args) {
                // Building Parameters
                List<NameValuePair> params = new ArrayList<NameValuePair>();
                // getting JSON string from URL
                JSONObject json = jParser.makeHttpRequest(url_all_events,
                        "GET", params);
                try {
                    // Checking for SUCCESS TAG
                    int success = json.getInt(CONNECTION_STATUS);
                    if (success == 1) {
                        // products found
                        // Getting Array of Products
                        Events = json.getJSONArray(TABLE_EVENT);
                        // looping through All Contacts
                        for (int i = 0; i < Events.length(); i++) {
                            JSONObject evt = Events.getJSONObject(i);
                            // Storing each json item in variable
                            id = evt.getString(pid);
                            group = evt.getString(COL_GROUP);
                            name = evt.getString(COL_NAME);
                            desc = evt.getString(COL_DESC);
                            date = evt.getString(COL_DATE);
                            time = evt.getString(COL_TIME);
                            // creating new HashMap
                            HashMap<String, String> map = new HashMap<String, String>();
                            // adding each child node to HashMap key => value
                            map.put(pid, id);
                            map.put(COL_GROUP, group);
                            map.put(COL_NAME, name);
                            map.put(COL_DESC, desc);
                            map.put(COL_DATE, date);
                            map.put(COL_TIME, time);
                            // adding HashList to ArrayList
                            eventsList.add(map);
                        }
                    } else {
                        // Options are not available or server is down.
                        // Dismiss the loading dialog and display an alert
                        // onPostExecute
                        pDialog.dismiss();
                    }
                } catch (JSONException e) {
                    e.printStackTrace();
                }
                return null;
            }
            protected void onPostExecute(String file_url) {
                // dismiss the dialog after getting all products
                pDialog.dismiss();
                // updating UI from Background Thread
                getActivity().runOnUiThread(new Runnable() {
                    public void run() {
                        ListAdapter adapter = new SimpleAdapter(getActivity(),
                                eventsList, R.layout.list_item, new String[] {
                                        pid, COL_GROUP, COL_NAME, COL_DATE, COL_TIME },
                                new int[] { R.id.pid, R.id.group, R.id.name, R.id.header,
                                        R.id.title2 });
                        setListAdapter(adapter);
                    }
                });
            }
        }
    }

活动详细信息类别：

public class EventDetails extends Activity {
    String pid;
    TextView EvtName, EvtDesc, EvtDate, EvtTime, Header;
    ImageView logo;
    private String url_event_details = "http://centrubook.eu.pn/eventDetails.php";
    private ProgressDialog pDialog;
    JSONParser jParser = new JSONParser();
    // JSON Node names
    private static final String CONNECTION_STATUS = "success";
    private static final String TABLE_EVENT = "Event";
    private static final String COL_PID = "pid";
    private static final String COL_NAME = "Event_Name";
    private static final String COL_DESC = "Event_Desc";
    private static final String COL_DATE = "Event_Date";
    private static final String COL_TIME = "Event_Time";
    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        switch (item.getItemId()) {
        // Respond to the action bar's Up/Home button
        case android.R.id.home:
            NavUtils.navigateUpFromSameTask(this);
            return true;
        }
        return super.onOptionsItemSelected(item);
    }
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.eventdetails);
        // ActionBar actionBar = getActionBar();
        // actionBar.setDisplayHomeAsUpEnabled(true);
        EvtName = (TextView) findViewById(R.id.BombaName);
        EvtDesc = (TextView) findViewById(R.id.BombaDesc);
        EvtDate = (TextView) findViewById(R.id.BombaDate);
        EvtTime = (TextView) findViewById(R.id.BombaTime);
        logo = (ImageView) findViewById(R.id.BombaLogo);
        Intent i = getIntent();
        pid = i.getStringExtra(COL_PID);
        new getEventDetails().execute();
    }
    class getEventDetails extends AsyncTask<String, String, String> {
        String name, desc, date, time;
        @Override
        protected void onPreExecute() {
            super.onPreExecute();
            pDialog = new ProgressDialog(EventDetails.this);
            pDialog.setMessage("Just a moment...");
            pDialog.setIndeterminate(false);
            pDialog.setCancelable(true);
            pDialog.show();
        }
        @Override
        protected String doInBackground(String... args) {
            // Check for success tag
            int success;
            try {
                List<NameValuePair> params = new ArrayList<NameValuePair>();
                params.add(new BasicNameValuePair("pid", pid));
                // getting product details by making HTTP request
                // Note that product details url will use GET request
                JSONObject json = jParser.makeHttpRequest(url_event_details,
                        "GET", params);
                // json success tag
                success = json.getInt(CONNECTION_STATUS);
                if (success == 1) {
                    // successfully received product details
                    JSONArray eventsObj = json.getJSONArray(TABLE_EVENT);
                    // get first product object from JSON Array
                    JSONObject details = eventsObj.getJSONObject(0);
                    name = details.getString(COL_NAME);
                    desc = details.getString(COL_DESC);
                    date = details.getString(COL_DATE);
                    time = details.getString(COL_TIME);
                } else {
                    // product with pid not found
                }
            } catch (JSONException e) {
                e.printStackTrace();
            }
            return null;
        }
        protected void onPostExecute(final String file_url) {
            pDialog.dismiss();
            runOnUiThread(new Runnable() {
                public void run() {
                    EvtName.setText(name);
                    EvtDesc.setText(desc);
                    EvtDate.setText(date);
                    EvtTime.setText(time);
                    logo.setImageResource(R.drawable.events);
                }
            });
        }
    }
}

希望这能有所帮助；）

Answer 5

我做了一个简单的JSONAdapter，如下所示：

public abstract class JSONAdapter extends BaseAdapter {
private JSONArray array;
@Override
public int getCount() {
    return array == null ? 0 : array.length();
}
@Override
public Object getItem(final int position) {
    if (array == null | array.length() < position) {
        return null;
    }
    try {
        return array.get(position);
    } catch (final JSONException e) {
        e.printStackTrace();
        return null;
    }
}
@Override
public long getItemId(final int position) {
    return position;
}
public JSONObject getObject(final int position) {
    return (JSONObject) getItem(position);
}
public void setData(final JSONArray data) {
    array = data;
    notifyDataSetChanged();
}
}

然后，当我需要它的特定实例时，我必须用我的具体需求覆盖适配器中的getView方法：

@Override
public View getView(final int position, final View convertView,
        final ViewGroup parent) {
    final View view;
    final ViewHolder holder;
    if (convertView != null) {
        view = convertView;
        holder = (ViewHolder) view.getTag();
    } else {
        view = context.getLayoutInflater().inflate(
                R.layout.<mylayout>, parent, false);
        holder = new ViewHolder();
        holder.name = (TextView) view.findViewById(R.id.name);
                    [...]
        view.setTag(holder);
    }
    final JSONObject jsonObj = getObject(position);
    holder.name.setText(jsonObj.optString("name"));
    [...]
    return view;
}

并设置这样的数据：

final JSONObject json = new JSONObject(jsonString);
adapter.setData(json.getJSONArray("projects"));