从 JSON 填充列表视图

Question

有谁知道动态加载 Json 的任何示例 数据到 ListView 中，我见过的大多数例子只是使用 某种静态数组。我需要加载 10 行 Json数据，然后在底部有一个load more..来获取 接下来 10 个等等 请使用 Json 的示例......

Answer 1

程序员布鲁斯是正确的，没有默认的方法可以做到这一点。然而，有一个非常干净和简单的方法来完成这个任务。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使用 JSON 数组填充 ListView，就像使用数据库记录填充 ListView 一样。

我建议熟悉使用 JSON 数据填充您选择的 Java 数据结构，并熟悉使用 ListViews，从不同的集合中使用不同的自定义行填充它们。

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

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，但是这篇文章解释了如何为我们其他不知道去哪里的人使用它从那里开始。

Answer 4

尝试以下操作：

JSON Parser 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：

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);

                }
            });
        }
    }
}

希望这会有所帮助；）

Answer 5

我制作了一个像这样的简单 JSONAdapter：

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，我必须根据我的具体需要重写适配器中的 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;
}

并设置如下数据：

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