Question

As I am a beginner to Android programming, I was trying to run some tutorials, but upon running the programs( the source code is available here: http://www.androidhive.info/2012/01/android-json-parsing-tutorial/ ) I got an error.

The program is supposed to read in data from a website and process it, but I think there is something wrong with the networking part.
I am fully aware there have been similar questions here on SO, yet I had no clue how to solve it, perhaps anyone could give solutions which I also can understand.

Strange NetworkOnMainThreadException in Android app?
This is a questions which was asked earlier and is identical to my problem, but I had no clue what they are trying to say there, i.e. “To fix you just need to move any thing that is touching the network to its own thread.” makes no sense to me whatsoever..
Can anyone please shed some light on this?

Answer 1

Use an AsyncTask to move your network operation off of the main/ui thread and onto a background/worker thread.

Expanding on the example from the tutorial, wrap the JSON stuff inside of an anonymous AsyncTask:

@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.main);

    new AsyncTask<Void, Void, JSONObject>() {

        protected JSONObject doInBackground(Void... args) {
            // Creating JSON Parser instance
            JSONParser jParser = new JSONParser();

            // getting JSON string from URL
            return jParser.getJSONFromUrl(url);
        }

        protected void onPostExecute(JSONObject json) {
            // Hashmap for ListView
            ArrayList<HashMap<String, String>> contactList = new ArrayList<HashMap<String, String>>();

            try {
                // Getting Array of Contacts
                contacts = json.getJSONArray(TAG_CONTACTS);

                // looping through All Contacts
                for(int i = 0; i < contacts.length(); i++){
                    JSONObject c = contacts.getJSONObject(i);

                    // Storing each json item in variable
                    String id = c.getString(TAG_ID);
                    String name = c.getString(TAG_NAME);
                    String email = c.getString(TAG_EMAIL);
                    String address = c.getString(TAG_ADDRESS);
                    String gender = c.getString(TAG_GENDER);

                    // Phone number is agin JSON Object
                    JSONObject phone = c.getJSONObject(TAG_PHONE);
                    String mobile = phone.getString(TAG_PHONE_MOBILE);
                    String home = phone.getString(TAG_PHONE_HOME);
                    String office = phone.getString(TAG_PHONE_OFFICE);

                    // creating new HashMap
                    HashMap<String, String> map = new HashMap<String, String>();

                    // adding each child node to HashMap key => value
                    map.put(TAG_ID, id);
                    map.put(TAG_NAME, name);
                    map.put(TAG_EMAIL, email);
                    map.put(TAG_PHONE_MOBILE, mobile);

                    // adding HashList to ArrayList
                    contactList.add(map);
                }
            } catch (JSONException e) {
                e.printStackTrace();
            }

            /**
             * Updating parsed JSON data into ListView
             * */
            ListAdapter adapter = new SimpleAdapter(this, contactList,
                    R.layout.list_item,
                    new String[] { TAG_NAME, TAG_EMAIL, TAG_PHONE_MOBILE }, new int[] {
                            R.id.name, R.id.email, R.id.mobile });

            setListAdapter(adapter);

            // selecting single ListView item
            ListView lv = getListView();

            // Launching new screen on Selecting Single ListItem
            lv.setOnItemClickListener(new OnItemClickListener() {

                @Override
                public void onItemClick(AdapterView<?> parent, View view,
                        int position, long id) {
                    // getting values from selected ListItem
                    String name = ((TextView) view.findViewById(R.id.name)).getText().toString();
                    String cost = ((TextView) view.findViewById(R.id.email)).getText().toString();
                    String description = ((TextView) view.findViewById(R.id.mobile)).getText().toString();

                    // Starting new intent
                    Intent in = new Intent(getApplicationContext(), SingleMenuItemActivity.class);
                    in.putExtra(TAG_NAME, name);
                    in.putExtra(TAG_EMAIL, cost);
                    in.putExtra(TAG_PHONE_MOBILE, description);
                    startActivity(in);
                }
            });
        }
    }.execute((Void) null);
}