How to display JSON format data from web server using recyclerview in android

Question

I am newbie in android also JSON.I am trying to displaying JSON format data from web server using recyclerviw.On my MainActivity Code i used HashMap inside ArrayList and I have parsed data from web server and put it into HashMap under ArrayList.I put id, name, email, mobile data in HashMap under ArrayList. But I want to display only email and mobile data using recyclerview. But I don't know how to display only email, and mobile data using recyclerview.

Here is my JSON Web Server Link: http://api.androidhive.info/contacts/

My full code is given below:

MainActivity code:

public class MainActivity extends AppCompatActivity {

    JSONArray contacts;
    Context context;


    ArrayList<HashMap<String, String>> contactList;
    public static final String TAG =MainActivity.class.getSimpleName();

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        RecyclerView recyclerView = findViewById(R.id.recyclerview);
        ArrayAdapter adapter = new ArrayAdapter(context,contactList,contacts);
        recyclerView.setAdapter(adapter);
        recyclerView.setLayoutManager(new LinearLayoutManager(this));

        new getContacts().execute();

    }

    private class getContacts extends AsyncTask<Void, Void, Void>{

        @Override
        protected void onPreExecute() {
            super.onPreExecute();
            Toast.makeText(getApplicationContext(),"JSON Data is" +
                    " downloading",Toast.LENGTH_LONG).show();
        }

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

            HttpHandler sh = new HttpHandler();
            String url = "http://api.androidhive.info/contacts/";
            String jsonStr = sh.makeServiceCall(url);
            Log.e(TAG,"Response from url: " + jsonStr);

            if(jsonStr != null){
                try{

                    JSONObject jsonObject = new JSONObject(jsonStr);

                     contacts = jsonObject.getJSONArray("contacts");

                    for (int i = 0; i < contacts.length(); i++){
                        JSONObject c = contacts.getJSONObject(i);

                        String id = c.getString("id");
                        String name = c.getString("name");
                        String email = c.getString("email");
                        String address = c.getString("address");
                        String gender = c.getString("gender");

                        JSONObject phone = c.getJSONObject("phone");
                        String mobile = phone.getString("mobile");
                        String home = phone.getString("home");
                        String office = phone.getString("office");

                        HashMap<String, String> contact = new HashMap<>();

                        contact.put("id", id);
                        contact.put("name", name);
                        contact.put("email", email);
                        contact.put("mobile", mobile);

                        contactList.add(contact);
                    }
                }catch (final JSONException e){
                    Log.e(TAG, "Json parsing error: " +e.getMessage());
                    runOnUiThread(new Runnable() {
                        @Override
                        public void run() {
                            Toast.makeText(getApplicationContext(),"Json parsing error: "
                                    + e.getMessage(),Toast.LENGTH_LONG).show();

                        }
                    });
                }
            }else {
                Log.e(TAG, "Couldn't get json from server.");
                runOnUiThread(new Runnable() {
                    @Override
                    public void run() {
                        Toast.makeText(getApplicationContext(),"Couldn't get json from server. Check LogCat for possible errors",
                                Toast.LENGTH_LONG).show();
                    }
                });
            }

            return null;
        }

        @Override
        protected void onPostExecute(Void aVoid) {
            super.onPostExecute(aVoid);
        }


    }
}

ArrayAdapter Code:

public class ArrayAdapter extends RecyclerView.Adapter<ArrayAdapter.MyViewHolder>{

    Context context;
    ArrayList<HashMap<String, String>> contactList;
    JSONArray contacts;

    public ArrayAdapter(Context context, ArrayList<HashMap<String, String>> contactList, JSONArray contacts) {
        this.context = context;
        this.contactList = contactList;
        this.contacts = contacts;
    }

    @NonNull
    @Override
    public MyViewHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
        LayoutInflater inflater = LayoutInflater.from(context);
        View v = inflater.inflate(R.layout.row_item,parent,false);

        return new  MyViewHolder(v);
    }

    @Override
    public void onBindViewHolder(@NonNull MyViewHolder holder, int position) {

            holder.email.setText((CharSequence) contactList.get(position));
            holder.mobile.setText((CharSequence) contactList.get(position));



    }

    @Override
    public int getItemCount() {
        return contacts.length();
    }

    public class MyViewHolder extends RecyclerView.ViewHolder {
        TextView email;
        TextView mobile;

        public MyViewHolder(@NonNull View itemView) {
            super(itemView);
            if(contacts.length() >= 2){
                email = itemView.findViewById(R.id.email);
                mobile = itemView.findViewById(R.id.mobile);
            }


        }
    }
}

HttpHandler Code:

public class HttpHandler {
    private static final String TAG = HttpHandler.class.getSimpleName();

    public HttpHandler() {
    }

    public String makeServiceCall(String reqUrl){

        String response = null;

        try {
            URL url = new URL(reqUrl);
            HttpURLConnection conn =(HttpURLConnection) url.openConnection();
            conn.setRequestMethod("GET");
            InputStream in = new BufferedInputStream(conn.getInputStream());
            response = convertStreamToString(in);

        }catch (MalformedURLException e){
            Log.e(TAG,"MalformException: " + e.getMessage());
        }catch (ProtocolException e){
            Log.e(TAG,"ProtocolException: " + e.getMessage());
        }catch (IOException e){
            Log.e(TAG, "IOException: " + e.getMessage());
        }

        return response;

    }

    private String convertStreamToString(InputStream is){
        BufferedReader reader = new BufferedReader(new InputStreamReader(is));
        StringBuilder sb = new StringBuilder();

        boolean line;

        try {
            while (line = reader.readLine() != null){
                sb.append(line).append('\n');
            }
        }catch (IOException e){
            e.printStackTrace();
        }finally {
            try {
                is.close();
            }catch (IOException e){
                e.printStackTrace();
            }
        }
        return sb.toString();
    }

}

Answer 1

In your onBindViewHolder method of arrayAdapter.class

Change this:

holder.email.setText((CharSequence) contactList.get(position));

With:

holder.email.setText((CharSequence) contactList.get(position).get("email"));

Do the same things for other item too

Answer 2

holder.email.setText((CharSequence) contactList.get(position).get("email"); holder.mobile.setText((CharSequence) contactList.get(position).get("mobile"); Get email and mobile from arraylist by key name

Answer 3

Try this

MainActivity

public class MainActivity extends AppCompatActivity {

private ArrayAdapter adapter;
public static final String TAG =MainActivity.class.getSimpleName();

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);

    RecyclerView recyclerView = findViewById(R.id.recyclerview);
    adapter = new ArrayAdapter(getApplicationContext());
    recyclerView.setAdapter(adapter);
    recyclerView.setLayoutManager(new LinearLayoutManager(this));
    new getContacts().execute();

}

    private class getContacts extends AsyncTask<Void, Void, List<HashMap<String, String>>> {

    @Override
    protected void onPreExecute() {
        super.onPreExecute();
        Toast.makeText(getApplicationContext(),"JSON Data is" +
                " downloading",Toast.LENGTH_LONG).show();
    }

    @Override
    protected List<HashMap<String, String>> doInBackground(Void... voids) {

        HttpHandler sh = new HttpHandler();
        String url = "http://api.androidhive.info/contacts/";
        String jsonStr = sh.makeServiceCall(url);
        Log.e(TAG,"Response from url: " + jsonStr);

        if(jsonStr != null){
            try{

                JSONObject jsonObject = new JSONObject(jsonStr);

                List<HashMap<String, String>> contactList = new ArrayList<>();

                JSONArray contacts = jsonObject.getJSONArray("contacts");

                for (int i = 0; i < contacts.length(); i++){
                    JSONObject c = contacts.getJSONObject(i);

                    String id = c.getString("id");
                    String name = c.getString("name");
                    String email = c.getString("email");
                    String address = c.getString("address");
                    String gender = c.getString("gender");

                    JSONObject phone = c.getJSONObject("phone");
                    String mobile = phone.getString("mobile");
                    String home = phone.getString("home");
                    String office = phone.getString("office");

                    HashMap<String, String> contact = new HashMap<>();

                    contact.put("id", id);
                    contact.put("name", name);
                    contact.put("email", email);
                    contact.put("mobile", mobile);

                    contactList.add(contact);
                }
                return contactList;
            }catch (final JSONException e){
                Log.e(TAG, "Json parsing error: " +e.getMessage());
                runOnUiThread(new Runnable() {
                    @Override
                    public void run() {
                        Toast.makeText(getApplicationContext(),"Json parsing error: "
                                + e.getMessage(),Toast.LENGTH_LONG).show();

                    }
                });
            }
        }else {
            Log.e(TAG, "Couldn't get json from server.");
            runOnUiThread(new Runnable() {
                @Override
                public void run() {
                    Toast.makeText(getApplicationContext(),"Couldn't get json from server. Check LogCat for possible errors",
                            Toast.LENGTH_LONG).show();
                }
            });
        }
        return null;
    }

    @Override
    protected void onPostExecute(List<HashMap<String, String>> result) {
        super.onPostExecute(result);
        if(result != null){
            adapter.add(result);
            adapter.notifyDataSetChanged();
        }
    }
}

}

ArrayAdapter

public class ArrayAdapter extends RecyclerView.Adapter<ArrayAdapter.MyViewHolder>{

Context context;
LayoutInflater inflater;
List<HashMap<String, String>> contactList;

public ArrayAdapter(Context context) {
    this.context = context;
    inflater = LayoutInflater.from(context);
    this.contactList = new ArrayList<>();
}

public void add(List<HashMap<String, String>> arg){
    contactList.addAll(arg);
}


@NonNull
@Override
public MyViewHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
    View v = inflater.inflate(R.layout.row_item,parent,false);

    return new  MyViewHolder(v);
}

@Override
public void onBindViewHolder(@NonNull MyViewHolder holder, int position) {
    HashMap<String, String> data = contactList.get(position);
    holder.bindData(data);
}

@Override
public int getItemCount() {
    return contactList.size();
}

public class MyViewHolder extends RecyclerView.ViewHolder {
    private TextView email;
    private TextView mobile;

    public MyViewHolder(@NonNull View itemView) {
        super(itemView);
        email = itemView.findViewById(R.id.email);
        mobile = itemView.findViewById(R.id.mobile);
    }

    public void bindData(HashMap<String, String> data){
        email.setText(data.get("email"));
        mobile.setText(data.get("mobile"));
    }
}

}