HttpURLConnection with JSON Parsing Android Example (Android Studio Project)

Download this project here : HttpURLConnection with JSONParsing

Most Network - Connected Android apps use HTTP to send and receive data.
The Android platform includes the HttpURLConnection client.

Before performing network related operations we need to check whether device is connected to network or not and then proceed to perform network operations.

Screenshot of the output:

AndroidManifest.xml:

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.ramsandroid.httpurlconnection">

    <uses-permission android:name="android.permission.INTERNET" />
    <uses-permission android:name="android.permission.ACCESS_NETWORK_STATE" />

    <application
        android:allowBackup="true"
        android:icon="@mipmap/ic_launcher"
        android:label="@string/app_name"
        android:supportsRtl="true"
        android:theme="@style/AppTheme">
        <activity android:name=".MainActivity">
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
    </application>

</manifest>

activity_main.xml:

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent">

    <ScrollView
        android:layout_width="match_parent"
        android:layout_height="match_parent">

        <TextView
            android:id="@+id/textview"
            android:layout_width="match_parent"
            android:layout_height="match_parent"
            android:textSize="20sp"/>
    </ScrollView>
</RelativeLayout>

MainActivity.java:
package com.ramsandroid.httpurlconnection;

import android.app.AlertDialog;
import android.app.ProgressDialog;
import android.content.Context;
import android.content.DialogInterface;
import android.net.ConnectivityManager;
import android.net.NetworkInfo;
import android.os.AsyncTask;
import android.os.StrictMode;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.widget.TextView;

import org.json.JSONArray;
import org.json.JSONException;
import org.json.JSONObject;

import java.io.BufferedInputStream;
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.net.HttpURLConnection;
import java.net.URL;

public class MainActivity extends AppCompatActivity {
    TextView textView;

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

        textView = (TextView) findViewById(R.id.textview);

        ConnectivityManager connMgr = (ConnectivityManager)
                getSystemService(Context.CONNECTIVITY_SERVICE);
        NetworkInfo networkInfo = connMgr.getActiveNetworkInfo();
        if (networkInfo != null && networkInfo.isConnected()) {
            MyAsync myAsync = new MyAsync();
            myAsync.execute();
        } else {
            AlertDialog.Builder builder = new AlertDialog.
                                                  Builder(MainActivity.this);
            builder.setTitle("Alert!");
            builder.setMessage("Please check your network connection");
            builder.setPositiveButton("OK", 
                                              new DialogInterface.OnClickListener() {
                @Override
                public void onClick(DialogInterface dialogInterface, int i) {
                    finish();
                }
            });
            builder.create().show();
        }
    }

    class MyAsync extends AsyncTask<Void, Void, String> {
        ProgressDialog progressDialog;

        @Override
        protected void onPreExecute() {
            super.onPreExecute();
            progressDialog = ProgressDialog.show(MainActivity.this, "downloading", "please wait");
        }

        @Override
        protected String doInBackground(Void... voids) {
            String result = null;
            try {
                URL url = new URL("http://api.androidhive.info/contacts/");
                HttpURLConnection urlConnection = (HttpURLConnection) url.openConnection();

                InputStream in = new BufferedInputStream(urlConnection.getInputStream());
                result = inputStreamToString(in);
            } catch (Exception e) {
                e.printStackTrace();
            }
            return result;
        }

        @Override
        protected void onPostExecute(String s) {
            super.onPostExecute(s);
            progressDialog.dismiss();
            try {
                JSONObject jsonObject = new JSONObject(s);
                JSONArray jsonArray = jsonObject.getJSONArray("contacts");
                for (int i = 0; i < jsonArray.length(); i++) {
                    String id = jsonArray.getJSONObject(i).getString("id");
                    String name = jsonArray.getJSONObject(i).getString("name");
                    String email = jsonArray.getJSONObject(i).getString("email");

                    String mobile = jsonArray.getJSONObject(i).getJSONObject("phone").getString("mobile");

                    textView.append(id + "\n");
                    textView.append(name + "\n");
                    textView.append(email + "\n");
                    textView.append(mobile + "\n\n");

                }

            } catch (JSONException e) {
                e.printStackTrace();
            }

        }
    }

    private String inputStreamToString(InputStream is) {
        String rLine = "";
        StringBuilder answer = new StringBuilder();

        InputStreamReader isr = new InputStreamReader(is);

        BufferedReader rd = new BufferedReader(isr);

        try {
            while ((rLine = rd.readLine()) != null) {
                answer.append(rLine);
            }
        } catch (IOException e) {
            e.printStackTrace();
        }
        return answer.toString();
    }
}