Android JSON parsing using Volley

Android JSON parsing using Volley

2014. 11. 5. 13:10ㆍPrograming/Android / Java

My previous article Android JSON Parsing Tutorial explains parsing json in a simple manner which got very good feedback and good ranking in search engines. In this tutorial I want to explain the same but in a easy & robust way using volley library.

If you want to know more about Volley and it’s benefits, go through Android working with Volley Library.

So let’s start this with a simple project.

Creating New Project

1. Create a new project in Eclipse from File ⇒ New ⇒ Android Application Project and fill all the required details.

I gave my project name as VolleyJson and package name as info.androidhive.volleyjson

2. Now create a new package under src folder by Right clicking on src ⇒ New ⇒ Package and give the package name as app. So my new package name will be info.androidhive.volleyjson.app

3. Download volley.jar and paste it in project’s libs folder.

4. Create a new class named AppController.java under app package. This is going to be a singleton class where we initialize all the volley core objects.

package info.androidhive.volleyjson.app;

import android.app.Application;
import android.text.TextUtils;

import com.android.volley.Request;
import com.android.volley.RequestQueue;
import com.android.volley.toolbox.Volley;
 
public class AppController extends Application {
 
    public static final String TAG = AppController.class.getSimpleName();
 
    private RequestQueue mRequestQueue;
 
    private static AppController mInstance;
 
    @Override
    public void onCreate() {
        super.onCreate();
        mInstance = this;
    }
 
    public static synchronized AppController getInstance() {
        return mInstance;
    }
 
    public RequestQueue getRequestQueue() {
        if (mRequestQueue == null) {
            mRequestQueue = Volley.newRequestQueue(getApplicationContext());
        }
 
        return mRequestQueue;
    }
 
    public <T> void addToRequestQueue(Request<T> req, String tag) {
        req.setTag(TextUtils.isEmpty(tag) ? TAG : tag);
        getRequestQueue().add(req);
    }
 
    public <T> void addToRequestQueue(Request<T> req) {
        req.setTag(TAG);
        getRequestQueue().add(req);
    }
 
    public void cancelPendingRequests(Object tag) {
        if (mRequestQueue != null) {
            mRequestQueue.cancelAll(tag);
        }
    }
}

5. AppController.java has to be executed when the app is launched. So add this class in your AndroidManifest.xml using name attribute for <application> tag.

Also add INTERNET permission as we need to make internet calls from the app.

<application
        android:name="info.androidhive.volleyjson.app.AppController">

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="info.androidhive.volleyjson"
    android:versionCode="1"
    android:versionName="1.0" >

    <uses-sdk
        android:minSdkVersion="8"
        android:targetSdkVersion="21" />
    
    <uses-permission android:name="android.permission.INTERNET"/>

    <application
        android:allowBackup="true"
        android:icon="@drawable/ic_launcher"
        android:label="@string/app_name"
        android:theme="@style/AppTheme" 
        android:name="info.androidhive.volleyjson.app.AppController">
        <activity
            android:name="info.androidhive.volleyjson.MainActivity"
            android:label="@string/app_name" >
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />

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

</manifest>

6. Open the layout file of main activity and add below code. (In my case my main activity layout file is activity_main.xml).

In this layout we are adding two Buttons and a TextView. In two Button, one is to invoke json object request and other is to invoke json array request. The TextView is used to display the parsed json response.

<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"
    tools:context="${relativePackage}.${activityClass}" >

    <Button
        android:id="@+id/btnObjRequest"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_centerHorizontal="true"
        android:layout_marginTop="50dp"
        android:paddingLeft="15dp"
        android:paddingRight="15dp"
        android:text="Make JSON Object Request" />

    <Button
        android:id="@+id/btnArrayRequest"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_centerHorizontal="true"
        android:layout_marginTop="50dp"
        android:paddingLeft="15dp"
        android:paddingRight="15dp"
        android:text="Make JSON Array Request"
        android:layout_below="@id/btnObjRequest" />
    
    <TextView
        android:id="@+id/txtResponse"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:layout_below="@id/btnArrayRequest"
        android:layout_marginTop="40px"
        android:padding="20dp" />

</RelativeLayout>

7. Now open main activity class MainActivity.java and add basic code like importing UI elements, adding button click events and initializing other objects.

Below you can notice two methods makeJsonObjectRequest() and makeJsonArrayRequest(). But these methods left empty for now, we’ll add code for these methods in next steps.

package info.androidhive.volleyjson;

import info.androidhive.volleyjson.R;
import info.androidhive.volleyjson.app.AppController;

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

import android.app.Activity;
import android.app.ProgressDialog;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.widget.Button;
import android.widget.TextView;
import android.widget.Toast;

import com.android.volley.Request.Method;
import com.android.volley.Response;
import com.android.volley.VolleyError;
import com.android.volley.VolleyLog;
import com.android.volley.toolbox.JsonArrayRequest;
import com.android.volley.toolbox.JsonObjectRequest;

public class MainActivity extends Activity {

	// json object response url
	private String urlJsonObj = "http://api.androidhive.info/volley/person_object.json";
	
	// json array response url
	private String urlJsonArry = "http://api.androidhive.info/volley/person_array.json";

	private static String TAG = MainActivity.class.getSimpleName();
	private Button btnMakeObjectRequest, btnMakeArrayRequest;

	// Progress dialog
	private ProgressDialog pDialog;

	private TextView txtResponse;

	// temporary string to show the parsed response
	private String jsonResponse;

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

		btnMakeObjectRequest = (Button) findViewById(R.id.btnObjRequest);
		btnMakeArrayRequest = (Button) findViewById(R.id.btnArrayRequest);
		txtResponse = (TextView) findViewById(R.id.txtResponse);

		pDialog = new ProgressDialog(this);
		pDialog.setMessage("Please wait...");
		pDialog.setCancelable(false);

		btnMakeObjectRequest.setOnClickListener(new View.OnClickListener() {

			@Override
			public void onClick(View v) {
				// making json object request
				makeJsonObjectRequest();
			}
		});

		btnMakeArrayRequest.setOnClickListener(new View.OnClickListener() {

			@Override
			public void onClick(View v) {
				// making json array request
				makeJsonArrayRequest();
			}
		});

	}

	/**
	 * Method to make json object request where json response starts wtih {
	 * */
	private void makeJsonObjectRequest() {
	}

	/**
	 * Method to make json array request where response starts with [
	 * */
	private void makeJsonArrayRequest() {
	}

	private void showpDialog() {
		if (!pDialog.isShowing())
			pDialog.show();
	}

	private void hidepDialog() {
		if (pDialog.isShowing())
			pDialog.dismiss();
	}
}

Normally json response will be of two types. It can be either json object or json array. If the json starts with {, it is considered to be JSON Object. As well if the json starts with [, then it is JSON Array.

Now we'll see how to make these requests individually.

Making JSON Object Request

8. Volley provides JsonObjectRequest class to make json object request. Add the below code in makeJsonObjectRequest() method. Here we are fetching the json by making a call to below url and parsing it. Finally the parsed response is appended to a string and displayed on the screen.

Sample JSON Object Response

URL: http://api.androidhive.info/volley/person_object.json

{
	"name" : "Ravi Tamada", 
	"email" : "ravi8x@gmail.com",
	"phone" : {
		"home" : "08947 000000",
		"mobile" : "9999999999"
	}
	
}

	/**
	 * Method to make json object request where json response starts wtih {
	 * */
	private void makeJsonObjectRequest() {

		showpDialog();

		JsonObjectRequest jsonObjReq = new JsonObjectRequest(Method.GET,
				urlJsonObj, null, new Response.Listener<JSONObject>() {

					@Override
					public void onResponse(JSONObject response) {
						Log.d(TAG, response.toString());

						try {
							// Parsing json object response
							// response will be a json object
							String name = response.getString("name");
							String email = response.getString("email");
							JSONObject phone = response.getJSONObject("phone");
							String home = phone.getString("home");
							String mobile = phone.getString("mobile");

							jsonResponse = "";
							jsonResponse += "Name: " + name + "\n\n";
							jsonResponse += "Email: " + email + "\n\n";
							jsonResponse += "Home: " + home + "\n\n";
							jsonResponse += "Mobile: " + mobile + "\n\n";

							txtResponse.setText(jsonResponse);

						} catch (JSONException e) {
							e.printStackTrace();
							Toast.makeText(getApplicationContext(),
									"Error: " + e.getMessage(),
									Toast.LENGTH_LONG).show();
						}
						hidepDialog();
					}
				}, new Response.ErrorListener() {

					@Override
					public void onErrorResponse(VolleyError error) {
						VolleyLog.d(TAG, "Error: " + error.getMessage());
						Toast.makeText(getApplicationContext(),
								error.getMessage(), Toast.LENGTH_SHORT).show();
						// hide the progress dialog
						hidepDialog();
					}
				});

		// Adding request to request queue
		AppController.getInstance().addToRequestQueue(jsonObjReq);
	}

Making JSON Array Request

9. Volley provides JsonArrayRequest class to make json array request. Add the below code in makeJsonArrayRequest() method.

Sample JSON Array Response

URL: http://api.androidhive.info/volley/person_array.json

[
	{
	"name" : "Ravi Tamada", 
	"email" : "ravi8x@gmail.com",
	"phone" : {
		"home" : "08947 000000",
		"mobile" : "9999999999"
	}
	},
	{
	"name" : "Tommy", 
	"email" : "tommy@gmail.com",
	"phone" : {
		"home" : "08946 000000",
		"mobile" : "0000000000"
	}
	}
]

	/**
	 * Method to make json array request where response starts with [
	 * */
	private void makeJsonArrayRequest() {

		showpDialog();

		JsonArrayRequest req = new JsonArrayRequest(urlJsonArry,
				new Response.Listener<JSONArray>() {
					@Override
					public void onResponse(JSONArray response) {
						Log.d(TAG, response.toString());

						try {
							// Parsing json array response
							// loop through each json object
							jsonResponse = "";
							for (int i = 0; i < response.length(); i++) {

								JSONObject person = (JSONObject) response
										.get(i);

								String name = person.getString("name");
								String email = person.getString("email");
								JSONObject phone = person
										.getJSONObject("phone");
								String home = phone.getString("home");
								String mobile = phone.getString("mobile");

								jsonResponse += "Name: " + name + "\n\n";
								jsonResponse += "Email: " + email + "\n\n";
								jsonResponse += "Home: " + home + "\n\n";
								jsonResponse += "Mobile: " + mobile + "\n\n\n";

							}

							txtResponse.setText(jsonResponse);

						} catch (JSONException e) {
							e.printStackTrace();
							Toast.makeText(getApplicationContext(),
									"Error: " + e.getMessage(),
									Toast.LENGTH_LONG).show();
						}

						hidepDialog();
					}
				}, new Response.ErrorListener() {
					@Override
					public void onErrorResponse(VolleyError error) {
						VolleyLog.d(TAG, "Error: " + error.getMessage());
						Toast.makeText(getApplicationContext(),
								error.getMessage(), Toast.LENGTH_SHORT).show();
						hidepDialog();
					}
				});

		// Adding request to request queue
		AppController.getInstance().addToRequestQueue(req);
	}

Now run the project and test it once. You should able to see the parsed json displayed on the screen upon tapping the json request buttons.

Complete Code

Here is the complete code of MainActivity.java

package info.androidhive.volleyjson;

import info.androidhive.volleyjson.R;
import info.androidhive.volleyjson.app.AppController;

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

import android.app.Activity;
import android.app.ProgressDialog;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.widget.Button;
import android.widget.TextView;
import android.widget.Toast;

import com.android.volley.Request.Method;
import com.android.volley.Response;
import com.android.volley.VolleyError;
import com.android.volley.VolleyLog;
import com.android.volley.toolbox.JsonArrayRequest;
import com.android.volley.toolbox.JsonObjectRequest;

public class MainActivity extends Activity {

	// json object response url
	private String urlJsonObj = "http://api.androidhive.info/volley/person_object.json";
	
	// json array response url
	private String urlJsonArry = "http://api.androidhive.info/volley/person_array.json";

	private static String TAG = MainActivity.class.getSimpleName();
	private Button btnMakeObjectRequest, btnMakeArrayRequest;

	// Progress dialog
	private ProgressDialog pDialog;

	private TextView txtResponse;

	// temporary string to show the parsed response
	private String jsonResponse;

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

		btnMakeObjectRequest = (Button) findViewById(R.id.btnObjRequest);
		btnMakeArrayRequest = (Button) findViewById(R.id.btnArrayRequest);
		txtResponse = (TextView) findViewById(R.id.txtResponse);

		pDialog = new ProgressDialog(this);
		pDialog.setMessage("Please wait...");
		pDialog.setCancelable(false);

		btnMakeObjectRequest.setOnClickListener(new View.OnClickListener() {

			@Override
			public void onClick(View v) {
				// making json object request
				makeJsonObjectRequest();
			}
		});

		btnMakeArrayRequest.setOnClickListener(new View.OnClickListener() {

			@Override
			public void onClick(View v) {
				// making json array request
				makeJsonArrayRequest();
			}
		});

	}

	/**
	 * Method to make json object request where json response starts wtih {
	 * */
	private void makeJsonObjectRequest() {

		showpDialog();

		JsonObjectRequest jsonObjReq = new JsonObjectRequest(Method.GET,
				urlJsonObj, null, new Response.Listener<JSONObject>() {

					@Override
					public void onResponse(JSONObject response) {
						Log.d(TAG, response.toString());

						try {
							// Parsing json object response
							// response will be a json object
							String name = response.getString("name");
							String email = response.getString("email");
							JSONObject phone = response.getJSONObject("phone");
							String home = phone.getString("home");
							String mobile = phone.getString("mobile");

							jsonResponse = "";
							jsonResponse += "Name: " + name + "\n\n";
							jsonResponse += "Email: " + email + "\n\n";
							jsonResponse += "Home: " + home + "\n\n";
							jsonResponse += "Mobile: " + mobile + "\n\n";

							txtResponse.setText(jsonResponse);

						} catch (JSONException e) {
							e.printStackTrace();
							Toast.makeText(getApplicationContext(),
									"Error: " + e.getMessage(),
									Toast.LENGTH_LONG).show();
						}
						hidepDialog();
					}
				}, new Response.ErrorListener() {

					@Override
					public void onErrorResponse(VolleyError error) {
						VolleyLog.d(TAG, "Error: " + error.getMessage());
						Toast.makeText(getApplicationContext(),
								error.getMessage(), Toast.LENGTH_SHORT).show();
						// hide the progress dialog
						hidepDialog();
					}
				});

		// Adding request to request queue
		AppController.getInstance().addToRequestQueue(jsonObjReq);
	}

	/**
	 * Method to make json array request where response starts with [
	 * */
	private void makeJsonArrayRequest() {

		showpDialog();

		JsonArrayRequest req = new JsonArrayRequest(urlJsonArry,
				new Response.Listener<JSONArray>() {
					@Override
					public void onResponse(JSONArray response) {
						Log.d(TAG, response.toString());

						try {
							// Parsing json array response
							// loop through each json object
							jsonResponse = "";
							for (int i = 0; i < response.length(); i++) {

								JSONObject person = (JSONObject) response
										.get(i);

								String name = person.getString("name");
								String email = person.getString("email");
								JSONObject phone = person
										.getJSONObject("phone");
								String home = phone.getString("home");
								String mobile = phone.getString("mobile");

								jsonResponse += "Name: " + name + "\n\n";
								jsonResponse += "Email: " + email + "\n\n";
								jsonResponse += "Home: " + home + "\n\n";
								jsonResponse += "Mobile: " + mobile + "\n\n\n";

							}

							txtResponse.setText(jsonResponse);

						} catch (JSONException e) {
							e.printStackTrace();
							Toast.makeText(getApplicationContext(),
									"Error: " + e.getMessage(),
									Toast.LENGTH_LONG).show();
						}

						hidepDialog();
					}
				}, new Response.ErrorListener() {
					@Override
					public void onErrorResponse(VolleyError error) {
						VolleyLog.d(TAG, "Error: " + error.getMessage());
						Toast.makeText(getApplicationContext(),
								error.getMessage(), Toast.LENGTH_SHORT).show();
						hidepDialog();
					}
				});

		// Adding request to request queue
		AppController.getInstance().addToRequestQueue(req);
	}

	private void showpDialog() {
		if (!pDialog.isShowing())
			pDialog.show();
	}

	private void hidepDialog() {
		if (pDialog.isShowing())
			pDialog.dismiss();
	}
}

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Complete Code

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