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RETROFIT HTTP LIBRARY - ANDROID TUTORIAL

Retrofit is same as Volley and it is definitely the better alternative to volley in terms of ease of use, performance, extensibility and other things. It is a type-­safe REST client for Android built by Square. Using this tool android developer can make all network stuff much more easier. 

Now let’s see the action of retrofit by creating a new project. As an example, we are going to download some json and show it in RecyclerView as a list.

Step 1. Create a new project in Android Studio

Step 2. Open build.gradle and add Retrofit
      compile 'com.squareup.retrofit2:retrofit:2.1.0'

make change over dependencies

dependencies {

    compile fileTree(dir: 'libs', include: ['*.jar'])
    testCompile 'junit:junit:4.12'
    compile 'com.android.support:appcompat-v7:23.1.1'
    compile 'com.android.support:design:23.1.0'
    compile 'com.squareup.retrofit2:retrofit:2.1.0'
    compile 'com.android.support:cardview-v7:23.1.1'
    compile 'com.github.bumptech.glide:glide:3.7.0'
}

Step 3. Since we are working with network operations we need to add INTERNET permissions in AndroidManifest.xml file
<uses-permission android:name="android.permission.INTERNET"/>

Step 4. Open activity_main.xml and replace the design

<?xml version="1.0" encoding="utf-8"?>

<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.ufours.retrofit_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>

Step 5. Create new xml card_view.xml and replace the design

<?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="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>

Step 6. Create an interface APICallInterface
public interface APICallInterface {
   @GET @Headers("Connection:close")
   Call<ResponseBody> callAPI(@Url String url);
   @GET @Headers("Connection:close")
   Call<ResponseBody> callAPI(@Url String url, @QueryMap Map<String, String> parameters);
   @POST @Headers("Connection:close")
   Call<ResponseBody> postToAPI(@Url String url, @Body RequestBody parameter);
   @PUT @Headers("Connection:close")
   Call<ResponseBody> putToAPI(@Url String url, @Body RequestBody parameter);

}


Step 7. Open MainActivity.java and replace the coding

public class MainActivity extends AppCompatActivity {


    private CoordinatorLayout coordinatorLayout;
    Retrofit retrofit;
    APICallInterface service;
    Call<ResponseBody> call = null;
    static ProgressDialog pDialog;
    private int mStatusCode;
    private static RecyclerView recyclerView;
    private RecyclerView.LayoutManager m_LayoutManager;

    String strTesti, strUrl;;
    public static String TAG_IMAGE_URL = "Image";
    public static String TAG_CONTENT = "content";
    ArrayList<HashMap<String, String>> arraySend = new ArrayList<>();
    CustomAdapter customAdapter;
    //Reponsecode
    public static final int SUCEESSRESPONSECODE = 200;
    public static final int FAILURERESPONSECODE = 204;
    public static final int INTERNALERRORRESPONSECODE = 500;
    public static final int ERRORRESPONSECODE = 400;

    String base_url = "http://YOUR_URL_HERE.com/";
    String url = "YOUR_METHOD_URL_HERE";

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

        retrofit = new Retrofit.Builder()
                .baseUrl(base_url)
                .build();
        service = retrofit.create(APICallInterface.class);

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

        if (isConnectingToInternet(MainActivity.this)) {
        loadImage();
        }else{
            alertbox(MainActivity.this,
                    getString(R.string.str_networkmessage),
                    getString(R.string.str_networktitlemessage));
        }
    }

    private void loadImage() {

        showDialog(MainActivity.this, "Loading");
        call = service.callAPI(url);

        call.enqueue(new Callback<ResponseBody>() {

            @Override
            public void onResponse(Call<ResponseBody> call, Response<ResponseBody> response) {

                try{
                    mStatusCode = response.code();

                    if (mStatusCode == SUCEESSRESPONSECODE) {

                        JSONArray resultarray = new JSONArray(response.body().string());
                        for (int i = 0; i < resultarray.length(); i++) {
                            JSONObject nmcdata = resultarray.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();

                    }else if (mStatusCode == FAILURERESPONSECODE) {
                        dismissDialog();
                        Snackbar snackbar = Snackbar.make(coordinatorLayout,
                                response.errorBody().string(), Snackbar.LENGTH_LONG);
                        snackbar.show();

                    } else {
                        if (mStatusCode == INTERNALERRORRESPONSECODE) {
                            dismissDialog();
                            Snackbar snackbar = Snackbar.make(coordinatorLayout,
                                    response.errorBody().string(), Snackbar.LENGTH_LONG);
                            snackbar.show();
                        }
                    }

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

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

            @Override
            public void onFailure(Call<ResponseBody> call, Throwable t) {
            }
        });
    }

    //internet_connection_check
    public boolean isConnectingToInternet(Context _context) {
        ConnectivityManager connectivity = (ConnectivityManager) _context
                .getSystemService(Context.CONNECTIVITY_SERVICE);

        NetworkInfo info = connectivity.getActiveNetworkInfo();
        if (info == null) {
            return false;
        } else
            return true;
    }

    public void alertbox(Context _context, String message, String title) {

        AlertDialog.Builder builder1 = new AlertDialog.Builder(_context);
        builder1.setTitle(title);
        builder1.setMessage(message);
        builder1.setCancelable(true);
        builder1.setPositiveButton("ok", new DialogInterface.OnClickListener() {
            public void onClick(DialogInterface dialog, int id) {
                dialog.cancel();
            }
        });

        AlertDialog alert11 = builder1.create();
        alert11.show();
    }

    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 brings the response as this

Step 8. Create a adapter class CustomAdapter.java 
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);

        }
    }
}

Now run the application and the output is as
________________________________________________________
Sourcecode for RetrofitSample.zip

Happy Coding...

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