How to: JSON Data Fetching and Parsing Android Studio Tutorial in Java

Here is the Summary!

We will only be using one activity named MainActivity.java in this whole project.  This activity will be doing the data fetching as well as displaying that JSON data. For this, we will be declaring the MainActivity.java in the AndroidManifest.xml file. Look at the AndroidManifest.xml file below.

AndroidManifest.xml.

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android" package="com.abhishekpanwar.receivedatajson">
  
  <uses-permission android:name="android.permission.INTERNET"/>
  
  <application android:allowBackup="true" android:icon="@mipmap/ic_launcher" android:label="@string/app_name" android:roundIcon="@mipmap/ic_launcher_round" 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>

Fetching the JSON data.

For this purpose, we will be declaring a class named
fetchData.java which will be extending from AsyncTask. AsyncTask is used for simple
asynchronous jobs like fetching data from a webserver etc. 

Asynchronous jobs are the jobs about which we don't know when it will be done executing, for example, we don't know here how much time it will take to fetch the JSON data as it depends on the internet speed, data size etc.

Hence we can't run asynchronous jobs in the main thread or else the UI of the app will be blocked. So we use AsyncTask to run these types of jobs in a different thread. Look at the fetchData.java file below which extends from AsyncTask.

fetchData.java

package com.abhishekpanwar.receivedatajson;

import android.os.AsyncTask;

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

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

/**
 * Created by Abhishek Panwar on 7/14/2017.
 */

public class fetchData extends AsyncTask {
    String data ="";
    String dataParsed = "";
    String singleParsed ="";
    @Override
    protected Void doInBackground(Void... voids) {
        try {
            URL url = new URL("https://api.myjson.com/bins/j5f6b");
            HttpURLConnection httpURLConnection = (HttpURLConnection) url.openConnection();
            InputStream inputStream = httpURLConnection.getInputStream();
            BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(inputStream));
            String line = "";
            while(line != null){
                line = bufferedReader.readLine();
                data = data + line;
            }

            JSONArray JA = new JSONArray(data);
            for(int i =0 ;i < JA.length(); i++){
                JSONObject JO = (JSONObject) JA.get(i);
                singleParsed =  "Name:" + JO.get("name") + "\n"+
                                "Password:" + JO.get("password") + "\n"+
                                "Contact:" + JO.get("contact") + "\n"+
                                "Country:" + JO.get("country") + "\n";

                dataParsed = dataParsed + singleParsed +"\n" ;


            }

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

        return null;
    }

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

        MainActivity.data.setText(this.dataParsed);

    }
}

We are doing the JSON data fetching job in the doInBackground() method. Once the JSON data is completely fetched, onPostExecute() method is called. Now in the onPostExecute method we are setting the content of the Textview in the MainActivity.java equal to the fetched JSON data.

In the MainActivity.java we will be starting the JSON data fetching process when a Button is
clicked. For this, we set up an OnClickListener to the Button.

MainActivity.java

package com.abhishekpanwar.receivedatajson;

import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.TextView;

public class MainActivity extends AppCompatActivity {
    Button click;
    public  static TextView data;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        click = (Button) findViewById(R.id.button);
        data = (TextView) findViewById(R.id.fetcheddata);

        click.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                  fetchData process = new fetchData();
                  process.execute();
            }
        });

    }
}

Thus, we learned how to fetch and parse JSON data in Android using AsyncTask. Subscribe to the newsletter for more such amazing content. Also visit codebrink.org for latest posts on coding.

Find the Source Code here: JSON Data Fetching Android Project