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.
AppController.java
package com.example.divakar.volleyjson; /** * Created by divakar on 9/4/2016. */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. Add internet permission to android manifest file because we are accessing JSON from web url;
<uses-permissionandroid:name="android.permission.INTERNET"/>
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.
activity_main.xml
<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 code.
MainActivity.java
package com.example.divakar.volleyjson;
import com.example.divakar.volleyjson.R;
import com.example.divakar.volleyjson.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();
}
}
above you can notice two methods makeJsonObjectRequest() and makeJsonArrayRequest().
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.
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" } } |
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" } }]
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.
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