Volley Library Fetching JSON Data from URL

In this tutorial, we will fetch the JSON data from the URL using Volley library. Volley is an HTTP Library which provides the facilities for the network connectivity of our app.

The advantages of using the Volley library are as follows:

More comfortable and faster request management.
It provides efficient network management.

Android Volley Fetching JSON Data from URL Example

In this example, we will load the JSON data from the URL using Volley library. The JSON data contains the String “name”, String “imageurl” and String “description” of tutorials. After fetching the data from the URL, they are displayed in ListView. You can refer more about JSON parsing tutorial at https://tutoraspire.com/android-json-parsing-tutorial.

Let’s create a JSON data which contains the following information.

JSON data at URL (provide your URL of information) = http://192.168.1.35:8080/jsondata/

  {  “tutorials”:[  {  “name”:”Java”,  “imageurl”:”https://tutoraspire.com/wp-content/static/images/logo/javahome.png”,  “description”:”Java is a high level, robust, object-oriented and secure programming language.”  },  {  “name”:”Android”,  “imageurl”:”https://tutoraspire.com/wp-content/static/images/logo/androidhome.png”,  “description”:”Android is a complete set of software for mobile devices.”  },  {  “name”:”Python”,  “imageurl”:”https://tutoraspire.com/wp-content/static/images/logo/pythonhome.png”,  “description”:”Python is a general purpose, dynamic, high level and interpreted programming language.”  },  {  “name”:”C++”,  “imageurl”:”https://tutoraspire.com/cpp/images/cpp-home.png”,  “description”:”C++ is an object-oriented programming language.”  }  ]  }  

The JSON data looks like as:

Volley Library Fetching JSON Data from URL

Create an activity_main.xml in layout and add the following code.

activity_main.xml

  <?xml version=”1.0″ encoding=”utf-8″?>  <android.support.constraint.ConstraintLayout xmlns:android=”http://schemas.android.com/apk/res/android”      xmlns:app=”http://schemas.android.com/apk/res-auto”      xmlns:tools=”http://schemas.android.com/tools”      android:layout_width=”match_parent”      android:layout_height=”match_parent”      tools:context=”example.tutoraspire.com.volleyreadimagejson.MainActivity”>        <ListView          android:id=”@+id/listView”          android:layout_width=”match_parent”          android:layout_height=”match_parent”          android:layout_marginBottom=”8dp”          android:layout_marginEnd=”8dp”          android:layout_marginStart=”8dp”          android:layout_marginTop=”8dp”          app:layout_constraintBottom_toBottomOf=”parent”          app:layout_constraintEnd_toEndOf=”parent”          app:layout_constraintStart_toStartOf=”parent”          app:layout_constraintTop_toTopOf=”parent” />        <ProgressBar          android:id=”@+id/progressBar”          android:layout_width=”wrap_content”          android:layout_height=”wrap_content”          android:layout_centerHorizontal=”true”          android:layout_centerVertical=”true”          android:layout_marginBottom=”292dp”          android:layout_marginEnd=”8dp”          android:layout_marginStart=”8dp”          android:layout_marginTop=”8dp”          android:visibility=”gone”          app:layout_constraintBottom_toBottomOf=”parent”          app:layout_constraintEnd_toEndOf=”parent”          app:layout_constraintStart_toStartOf=”parent”          app:layout_constraintTop_toTopOf=”parent” />    </android.support.constraint.ConstraintLayout>  

Now, create a list_item.xml file in the layout directory which contains the row items for ListView. This contains one ImageView for image display and two TextView for text display.

list_item.xml

  <?xml version=”1.0″ encoding=”utf-8″?>  <LinearLayout xmlns:android=”http://schemas.android.com/apk/res/android”      android:layout_width=”match_parent”      android:layout_height=”match_parent”      android:padding=”16dp”      android:orientation=”vertical”>      <LinearLayout          android:layout_width=”match_parent”          android:layout_height=”match_parent”          android:orientation=”horizontal”>          <ImageView              android:id=”@+id/imageView”              android:layout_width=”50dp”              android:layout_height=”50dp”              android:src=”@drawable/placeholder”              android:contentDescription=”image view” />          <TextView              android:id=”@+id/textViewName”              android:layout_width=”match_parent”              android:layout_height=”wrap_content”              android:text=”title”              android:textAppearance=”@style/Base.TextAppearance.AppCompat.Large” />      </LinearLayout>          <TextView          android:id=”@+id/textViewImageUrl”          android:layout_width=”match_parent”          android:layout_height=”wrap_content”          android:text=”url”          android:autoLink=”web”          android:textColor=”#08308e” />      </LinearLayout>  

Create a data model class with name Tutorial.java and information String “name”, String “imageurl” and String “description”.

Tutorial.java

  package example.tutoraspire.com.volleyreadimagejson;    public class Tutorial {      String name, imageUrl, description;        public Tutorial(String name, String imageUrl, String description) {          this.name = name;          this.imageUrl = imageUrl;          this.description = description;      }      public String getName() {          return name;      }      public String getImageUrl() {          return imageUrl;      }      public String getDescription() {          return description;      }  }  

Create a custom adapter class named as MyAdapter.java and extend ArrayAdapter to handle the custom ListView. In this class we are calling an anonymous class new ImageDownloaderTask(holder.imageView).execute(imageUrl) to download images from URL.

MyAdapter.java

  package example.tutoraspire.com.volleyreadimagejson;    import android.app.ProgressDialog;  import android.content.Context;  import android.graphics.Bitmap;  import android.view.LayoutInflater;  import android.view.View;  import android.view.ViewGroup;  import android.widget.ArrayAdapter;  import android.widget.ImageView;  import android.widget.TextView;  import java.util.List;      public class MyAdapter extends ArrayAdapter {      //the tutorial list that will be displayed      private List tutorialList;      private Bitmap bitmap;      private Context mCtx;      //here we are getting the tutoriallist and context      //so while creating the object of this adapter class we need to give tutoriallist and context      public MyAdapter(List tutorialList, Context mCtx) {          super(mCtx, R.layout.list_item, tutorialList);          this.tutorialList = tutorialList;          this.mCtx = mCtx;      }        //this method will return the list item      @Override      public View getView(int position, View convertView, ViewGroup parent) {          //getting the layoutinflater          ViewHolder holder;          LayoutInflater inflater = LayoutInflater.from(mCtx);          convertView = inflater.inflate(R.layout.list_item, null, true);          holder = new ViewHolder();          //getting text views          holder.textViewName = convertView.findViewById(R.id.textViewName);          holder.textDescription = convertView.findViewById(R.id.textViewImageUrl);          holder.imageView = convertView.findViewById(R.id.imageView);            convertView.setTag(holder);          //Getting the tutorial for the specified position          Tutorial tutorial = tutorialList.get(position);          String imageUrl = tutorial.getImageUrl();          String tutorialDescription = tutorial.getDescription();          String tutorialTitle = tutorial.getName();            holder.textViewName.setText(tutorialTitle);          holder.textDescription.setText(tutorialDescription);            if (holder.imageView != null) {              /*————-fatching image————*/;              new ImageDownloaderTask(holder.imageView).execute(imageUrl);          }          holder.imageView.setImageBitmap(bitmap);          return convertView;      }      static class ViewHolder {          TextView textViewName;          TextView textDescription;          ImageView imageView;      }  }  

Add the following library files in the build.gradle file.

build.gradle

  android {  useLibrary ‘org.apache.http.legacy’  }    dependencies {  compile ‘com.android.volley:volley:1.0.0’  compile ‘org.apache.httpcomponents:httpcore:4.4.1’  compile ‘org.apache.httpcomponents:httpclient:4.5’  }  

Creating an anonymous class ImageDownloaderTask.java which extends AsyncTask<>. This class downloads (or fetch) the images from URL while executing doInbackground() method and returns the result (bitmap) to onPostExecute(). In onPostExecute() method, the bitmap are set to the ImageView.

ImageDownloaderTask.java

  package example.tutoraspire.com.volleyreadimagejson;    import java.io.InputStream;  import java.lang.ref.WeakReference;  import java.net.HttpURLConnection;  import java.net.URL;  import org.apache.http.HttpStatus;  import android.graphics.Bitmap;  import android.graphics.BitmapFactory;  import android.graphics.drawable.Drawable;  import android.os.AsyncTask;  import android.util.Log;  import android.widget.ImageView;    public class ImageDownloaderTask extends AsyncTask {        private final WeakReference imageViewReference;      public ImageDownloaderTask(ImageView imageView) {          imageViewReference = new WeakReference(imageView);      }      @Override      protected Bitmap doInBackground(String… params) {          return downloadBitmap(params[0]);      }      @Override      protected void onPostExecute(Bitmap bitmap) {          if (isCancelled()) {              bitmap = null;          }          if (imageViewReference != null) {              ImageView imageView = imageViewReference.get();              if (imageView != null) {                  if (bitmap != null) {                      imageView.setImageBitmap(bitmap);                  } else {                      Drawable placeholder = imageView.getContext().getResources().getDrawable(R.drawable.placeholder);                      imageView.setImageDrawable(placeholder);                  }              }          }      }        private Bitmap downloadBitmap(String imageUrl) {          HttpURLConnection urlConnection = null;          try {              URL uri = new URL(imageUrl);              urlConnection = (HttpURLConnection) uri.openConnection();                int statusCode = urlConnection.getResponseCode();              if (statusCode != HttpStatus.SC_OK) {                  return null;              }              InputStream inputStream = urlConnection.getInputStream();              if (inputStream != null) {                  Bitmap bitmap = BitmapFactory.decodeStream(inputStream);                  return bitmap;              }          }          catch (Exception e) {              urlConnection.disconnect();              Log.w(“ImageDownloader”, “Error downloading image from ” + imageUrl);          }          finally {              if (urlConnection != null) {                  urlConnection.disconnect();              }          }          return null;      }  }  ,>

In MainActivity.java class, we are fetching and parsing the JSON data from the URL using Volley.

MainActivity.java

  package example.tutoraspire.com.volleyreadimagejson;    import android.support.v7.app.AppCompatActivity;  import android.os.Bundle;  import android.view.View;  import android.widget.ListView;  import android.widget.ProgressBar;  import android.widget.Toast;  import com.android.volley.Request;  import com.android.volley.RequestQueue;  import com.android.volley.Response;  import com.android.volley.VolleyError;  import com.android.volley.toolbox.StringRequest;  import com.android.volley.toolbox.Volley;  import org.json.JSONArray;  import org.json.JSONException;  import org.json.JSONObject;  import java.util.ArrayList;  import java.util.List;    public class MainActivity extends AppCompatActivity {        ListView listView;      private static final String JSON_URL = “http://192.168.1.35:8080/jsondata/”;      //the tutorial list where we will store all the tutorial objects after parsing json      List tutorialList;        @Override      protected void onCreate(Bundle savedInstanceState) {          super.onCreate(savedInstanceState);          setContentView(R.layout.activity_main);            listView = (ListView) findViewById(R.id.listView);          tutorialList = new ArrayList<>();          //this method will fetch and parse the data          loadTutorialList();      }        private void loadTutorialList() {          //getting the progressbar          final ProgressBar progressBar = (ProgressBar) findViewById(R.id.progressBar);          progressBar.setVisibility(View.VISIBLE);            //creating a string request to send request to the url          StringRequest stringRequest = new StringRequest(Request.Method.GET, JSON_URL,                  new Response.Listener() {                      @Override                      public void onResponse(String response) {                          //hiding the progressbar after completion                          progressBar.setVisibility(View.INVISIBLE);                              try {                              //getting the whole json object from the response                              JSONObject obj = new JSONObject(response);                                //we have the array named tutorial inside the object                              //so here we are getting that json array                              JSONArray tutorialsArray = obj.getJSONArray(“tutorials”);                                //now looping through all the elements of the json array                              for (int i = 0; i < tutorialsArray.length(); i++) {                                  //getting the json object of the particular index inside the array                                  JSONObject tutorialsObject = tutorialsArray.getJSONObject(i);                                    //creating a tutorial object and giving them the values from json object                                  Tutorial tutorial = new Tutorial(tutorialsObject.getString(“name”), tutorialsObject.getString(“imageurl”),tutorialsObject.getString(“description”));                                    //adding the tutorial to tutoriallist                                  tutorialList.add(tutorial);                              }                                //creating custom adapter object                              MyAdapter adapter = new MyAdapter(tutorialList, getApplicationContext());                                //adding the adapter to listview                              listView.setAdapter(adapter);                            } catch (JSONException e) {                              e.printStackTrace();                          }                      }                  },                  new Response.ErrorListener() {                      @Override                      public void onErrorResponse(VolleyError error) {                          //displaying the error in toast if occur                          Toast.makeText(getApplicationContext(), error.getMessage(), Toast.LENGTH_SHORT).show();                      }                  });            //creating a request queue          RequestQueue requestQueue = Volley.newRequestQueue(this);            //adding the string request to request queue          requestQueue.add(stringRequest);      }  }  

Add the Internet permission in AndroidManifest.xml

AndroidManifest.xml

Output:

Volley Library Fetching JSON Data from URL

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Volley Library Fetching JSON Data from URL

Volley Library Fetching JSON Data from URL

Android Volley Fetching JSON Data from URL Example

activity_main.xml

list_item.xml

Tutorial.java

MyAdapter.java

build.gradle

ImageDownloaderTask.java

MainActivity.java

AndroidManifest.xml

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