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Volley Library Example - Android Tutorial

What is Volley library exactly for?

Android volley is a networking library was introduced to make networking calls much easier, faster without writing tons of code. By default all the volley network calls works asynchronously, so we don’t have to worry about using asynctask anymore.


Advantages of using Volley:


  • Volley automatically schedule all network requests. It means that Volley will be taking care of all the network requests your app executes for fetching response or image from web.
  • Volley provides transparent disk and memory caching.
  • Volley provides powerful cancellation request API. It means that you can cancel a single request or you can set blocks or scopes of requests to cancel.
  • Volley provides powerful customization abilities.
  • Volley provides Debugging and tracing tools.

How to add Volley Library?

Open build.gradle located under your app module and add below dependencies.

compile 'com.mcxiaoke.volley:library:1.0.19'

After adding the dependencies Sync the project.

Now let’s see this in action by creating a new project.


1. Add dependencies


In this example, we gave request via Volley and got Images and Texts as a response.
To display Images in RecyclerView and CardView we have to add required dependencies, now it looks as,

build.gradle
dependencies {
compile fileTree(dir: 'libs', include: ['*.jar']
compile 'com.android.support:appcompat-v7:23.1.0'
compile 'com.mcxiaoke.volley:library:1.0.19'
compile 'com.android.support:recyclerview-v7:23.1.1'
compile 'com.android.support:cardview-v7:23.1.1'
compile 'com.github.bumptech.glide:glide:3.7.0'
}

2. Open activity_main.xml and replace with the following

<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="com.mrbrown.volley_sample.MainActivity">

    <android.support.v7.widget.RecyclerView
        android:id="@+id/idRecycler"
        android:layout_width="match_parent"
        android:layout_height="match_parent">
    </android.support.v7.widget.RecyclerView>
</RelativeLayout>

3. Now create the new xml file to implement CardView, here used as card_view.xml

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:padding="1dp">
    <android.support.v7.widget.CardView
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:id="@+id/card_view">
        <RelativeLayout
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:padding="5dp">
            <ImageView
                android:layout_width="100dp"
                android:layout_height="100dp"
                android:id="@+id/person_photo"
                android:layout_alignParentLeft="true"
                android:layout_alignParentTop="true"
                android:layout_marginRight="16dp" />
            <TextView
                android:layout_width="match_parent"
                android:layout_height="wrap_content"
                android:id="@+id/person_name"
                android:layout_toRightOf="@+id/person_photo"
                android:layout_alignParentTop="true" />
        </RelativeLayout>
    </android.support.v7.widget.CardView>
</LinearLayout>

4. Open the MainActivity.java

There are 2 main classes:
1. Request queue
2. Request

Replace the MainActivity.java with the following


public class MainActivity extends AppCompatActivity {

    String JsonURL ="ENTER YOUR URL HERE";
    RequestQueue requestQueue;
    public static String TAG_IMAGE_URL = "Image";
    public static String TAG_CONTENT = "content";
    String strTesti;
    String strUrl;
    ArrayList<HashMap<String, String>> arraySend = new ArrayList<>();
    static ProgressDialog pDialog;
    private static RecyclerView recyclerView;
    private RecyclerView.LayoutManager m_LayoutManager;
    CustomAdapter customAdapter;

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

        //Request queue
        requestQueue = Volley.newRequestQueue(this);

        recyclerView = (RecyclerView)findViewById(R.id.idRecycler);
        recyclerView.setHasFixedSize(true);
        m_LayoutManager = new LinearLayoutManager(this);
        recyclerView.setLayoutManager(m_LayoutManager);

        //Request
        JsonArrayRequest arrreq = new JsonArrayRequest(Request.Method.GET, JsonURL,
                new Response.Listener<JSONArray>() {
                    @Override
                    public void onResponse(JSONArray response) {
                        showDialog(MainActivity.this, "Loading");

                        try{
                            for (int i = 0; i < response.length(); i++) {
                                JSONObject nmcdata = response.getJSONObject(i);

                                strUrl = nmcdata.getString(TAG_IMAGE_URL);
                                strTesti = nmcdata.getString(TAG_CONTENT);

                                HashMap<String, String> objMap = new HashMap<>();
                                objMap.put(TAG_IMAGE_URL, strUrl);
                                objMap.put(TAG_CONTENT, strTesti);

                                arraySend.add(objMap);
                            }
                            dismissDialog();
                        } catch(  JSONException e){
                            e.printStackTrace();
                        }

                        if (arraySend.size() > 0) {
                            customAdapter = new CustomAdapter(MainActivity.this, arraySend, recyclerView);
                            recyclerView.setAdapter(customAdapter);

                        }
                    }
                },

        new Response.ErrorListener(){

            @Override
            public void onErrorResponse(VolleyError error) {
                dismissDialog();
                Log.e("error",error.toString());
            }
        }
        );
        requestQueue.add(arrreq);
    }

    public static void showDialog(Context mContext, String strMessage) {
        try {
            if (pDialog != null)
                if (pDialog.isShowing())
                    pDialog.dismiss();
            pDialog = ProgressDialog.show(mContext, "", strMessage, true);
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

    public static void dismissDialog() {
        try {
            if (pDialog.isShowing())
                pDialog.dismiss();
        } catch (Exception e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
    }
}

URL used here gave the response like this 


5. Create a new class CustomAdapter.java to set the images using Recycler View



public class CustomAdapter extends RecyclerView.Adapter{
    RecyclerView mrecyclerview;
    static Context context;
    ArrayList<HashMap<String, String>> Items = new ArrayList<>();

    public CustomAdapter(MainActivity context, ArrayList<HashMap<String, String>> arraySend, RecyclerView recyclerView) {
        this.context = context;
        mrecyclerview = recyclerView;
        Items = arraySend;
    }

    @Override
    public RecyclerView.ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
        RecyclerView.ViewHolder vh;
        View itemLayoutView = LayoutInflater.from(parent.getContext())
                .inflate(R.layout.card_view, null);

        vh = new ViewHolder(itemLayoutView);
        return vh;
    }

    @Override
    public void onBindViewHolder(RecyclerView.ViewHolder holder, int position) {

        try {

            final HashMap<String, String> tempMap = Items.get(position);

            ((ViewHolder) holder).txtConten.setText(tempMap
                    .get(MainActivity.TAG_CONTENT));

            String urlImg = tempMap
                    .get(MainActivity.TAG_IMAGE_URL);
            Glide.with(context)
                    .load(urlImg)
                    .into(((ViewHolder) holder).imgUrl);

        }catch (NullPointerException e) {
            e.printStackTrace();
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

    @Override
    public int getItemCount() {
        return Items.size();
    }

    private class ViewHolder extends RecyclerView.ViewHolder {
        public TextView txtConten;
        ImageView imgUrl;
        CardView cardview;

        public ViewHolder(View itemLayoutView) {
            super(itemLayoutView);

            cardview = (CardView) itemLayoutView.findViewById(R.id.card_view);
            imgUrl = (ImageView) itemLayoutView.findViewById(R.id.person_photo);
            txtConten = (TextView) itemLayoutView.findViewById(R.id.person_name);

        }
    }
}

6. Give permissions in Manifest.xml
<uses-permission android:name="android.permission.INTERNET" />
<uses-permission android:name="android.permission.ACCESS_WIFI_STATE" />
<uses-permission android:name="android.permission.ACCESS_NETWORK_STATE" />

Now run the application and get the response output as,
__________________________________________________________________
Source code for Volley Library.zip

Happy Coding...



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