Android Tutorial: How to Parse/Read JSON Data Into a Android ListView

Today we get on with our series that will connect our Android applications to internet webservices!

Next up in line: from JSON to a Listview. A lot of this project is identical to the previous post in this series so try to look there first if you have any problems. On the bottom of the post ill add the Eclipse project with the source.

For this example i made use of an already existing JSON webservice located here.

This is a piece of the JSON array that gets returned:

{"earthquakes": [    {        "eqid": "c0001xgp",        "magnitude": 8.8,        "lng": 142.369,        "src": "us",        "datetime": "2011-03-11 04:46:23",        "depth": 24.4,        "lat": 38.322  },  {        "eqid": "2007hear",        "magnitude": 8.4,        "lng": 101.3815,        "src": "us",        "datetime": "2007-09-12 09:10:26",        "depth": 30,        "lat": -4.5172  }<--more -->]}

So how do we get this data into our application! Behold our getJSON class!

getJSON(String url)

public static JSONObject getJSONfromURL(String url){//initializeInputStream is = null;String result = "";JSONObject jArray = null;//http posttry{HttpClient httpclient = new DefaultHttpClient();HttpPost httppost = new HttpPost(url);HttpResponse response = httpclient.execute(httppost);HttpEntity entity = response.getEntity();is = entity.getContent();}catch(Exception e){Log.e("log_tag", "Error in http connection "+e.toString());}//convert response to stringtry{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();result=sb.toString();}catch(Exception e){Log.e("log_tag", "Error converting result "+e.toString());}//try parse the string to a JSON objecttry{        jArray = new JSONObject(result);}catch(JSONException e){Log.e("log_tag", "Error parsing data "+e.toString());}return jArray;} 

The code above can be divided in 3 parts.

1. the first part makes the HTTP call
2. the second part converts the stream into a String
3. the third part converts the string to a JSPNObject

Now we only have to implement this into out ListView. We can use the same method as in the XML tutorial. We make a HashMap that stores our data and we put JSON values in the HashMap. After that we will bind that HashMap to a SimpleAdapter. Here is how its done:

Implementation

ArrayList<HashMap<String, String>> mylist = new ArrayList<HashMap<String, String>>();//Get the data (see above)JSONObject json =JSONfunctions.getJSONfromURL("http://api.geonames.org/postalCodeSearchJSON?formatted=true&postalcode=9791&maxRows=10&username=demo&style=full");       try{//Get the element that holds the earthquakes ( JSONArray )JSONArray  earthquakes = json.getJSONArray("earthquakes");             //Loop the Array        for(int i=0;i < earthquakes.length();i++){        HashMap<String, String> map = new HashMap<String, String>();        JSONObject e = earthquakes.getJSONObject(i);        map.put("id",  String.valueOf(i));        map.put("name", "Earthquake name:" + e.getString("eqid"));        map.put("magnitude", "Magnitude: " +  e.getString("magnitude"));        mylist.add(map);}       }catch(JSONException e)        {        Log.e("log_tag", "Error parsing data "+e.toString());       }

 After this we only need to make up the Simple Adapter

ListAdapter adapter = new SimpleAdapter(this, mylist , R.layout.main,                        new String[] { "name", "magnitude" },                        new int[] { R.id.item_title, R.id.item_subtitle });        setListAdapter(adapter);        final ListView lv = getListView();        lv.setTextFilterEnabled(true);        lv.setOnItemClickListener(new OnItemClickListener() {        public void onItemClick(AdapterView<?> parent, View view, int position, long id) {        @SuppressWarnings("unchecked")        Toast.makeText(Main.this, "ID '" + o.get("id") + "' was clicked.", Toast.LENGTH_SHORT).show(); }});

Now we have a ListView filled with JSON data!

Here is the Eclipse project: source code

Have fun playing around with it.