Retrofit API Tutorial in Android

Retrofit API Tutorial in Android



Retrofit is an awesome type-safe HTTP client for Android and Java built by awesome folks at Square. Retrofit makes it easy to consume JSON or XML data which is parsed into Plain Old Java Objects (POJOs).

It makes it relatively easy to retrieve and upload JSON (or other structured data) via a REST based web service.

In Retrofit you configure which converter is used for the data serialization.

Retrofit uses the OkHttp library for HTTP requests.




Output Screen


Add Dependency in Gradle:
implementation 'com.google.android.material:material:1.1.0'

implementation 'com.squareup.retrofit2:retrofit:2.3.0'

implementation 'com.squareup.retrofit2:converter-gson:2.3.0'




Geo.java
package com.example.helloworld;

import com.google.gson.annotations.SerializedName;

public class Geo {
    @SerializedName("lat")
    private String lat;
    @SerializedName("lng")
    private String lng;

    public Geo(String lat, String lng) {
        this.lat = lat;
        this.lng = lng;
    }

    public String getLat() {
        return lat;
    }

    public void setLat(String lat) {
        this.lat = lat;
    }

    public String getLng() {
        return lng;
    }

    public void setLng(String lng) {
        this.lng = lng;
    }
}

Address.java
package com.example.helloworld;

import com.google.gson.annotations.SerializedName;

public class Address {
    @SerializedName("street")
    private String street;
    @SerializedName("suite")
    private String suite;
    @SerializedName("city")
    private String city;
    @SerializedName("zipcode")
    private String zipcode;
    @SerializedName("geo")
    private Geo geo;

    public Address(String street, String suite, String city, String zipcode, Geo geo) {
        this.street = street;
        this.suite = suite;
        this.city = city;
        this.zipcode = zipcode;
        this.geo = geo;
    }

    public String getStreet() {
        return street;
    }

    public void setStreet(String street) {
        this.street = street;
    }

    public String getSuite() {
        return suite;
    }

    public void setSuite(String suite) {
        this.suite = suite;
    }

    public String getCity() {
        return city;
    }

    public void setCity(String city) {
        this.city = city;
    }

    public String getZipcode() {
        return zipcode;
    }

    public void setZipcode(String zipcode) {
        this.zipcode = zipcode;
    }

    public Geo getGeo() {
        return geo;
    }

    public void setGeo(Geo geo) {
        this.geo = geo;
    }
}

Company.java
package com.example.helloworld;

import com.google.gson.annotations.SerializedName;

public class Company {
    @SerializedName("name")
    private String name;
    @SerializedName("catchPhrase")
    private String catchPhrase;
    @SerializedName("bs")
    private String bs;

    public Company(String name, String catchPhrase, String bs) {
        this.name = name;
        this.catchPhrase = catchPhrase;
        this.bs = bs;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public String getCatchPhrase() {
        return catchPhrase;
    }

    public void setCatchPhrase(String catchPhrase) {
        this.catchPhrase = catchPhrase;
    }

    public String getBs() {
        return bs;
    }

    public void setBs(String bs) {
        this.bs = bs;
    }
}

User.java
package com.example.helloworld;

import com.google.gson.annotations.SerializedName;

public class User {
    @SerializedName("id")
    private int id;
    @SerializedName("name")
    private String name;
    @SerializedName("username")
    private String username;
    @SerializedName("email")
    private String email;
    @SerializedName("phone")
    private String phone;
    @SerializedName("website")
    private String website;
    @SerializedName("company")
    private Company company;
    @SerializedName("address")
    private Address address;

    public User(int id, String name, String username, String email, String phone, 
                String website, Company company, Address address) {
        this.id = id;
        this.name = name;
        this.username = username;
        this.email = email;
        this.phone = phone;
        this.website = website;
        this.company = company;
        this.address = address;
    }

    public Company getCompany() {
        return company;
    }

    public void setCompany(Company company) {
        this.company = company;
    }

    public Address getAddress() {
        return address;
    }

    public void setAddress(Address address) {
        this.address = address;
    }

    public int getId() {
        return id;
    }

    public void setId(int id) {
        this.id = id;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public String getUsername() {
        return username;
    }

    public void setUsername(String username) {
        this.username = username;
    }

    public String getEmail() {
        return email;
    }

    public void setEmail(String email) {
        this.email = email;
    }

    public String getPhone() {
        return phone;
    }

    public void setPhone(String phone) {
        this.phone = phone;
    }

    public String getWebsite() {
        return website;
    }

    public void setWebsite(String website) {
        this.website = website;
    }
}

SingleTask.java
package com.example.helloworld;

import android.app.Application;

import retrofit2.Retrofit;
import retrofit2.converter.gson.GsonConverterFactory;

public class SingleTask extends Application {
    private static Retrofit retrofit;
    private static final String BASE_URL = "https://jsonplaceholder.typicode.com";

    @Override
    public void onCreate() {
        super.onCreate();
        if (retrofit == null) {
            retrofit = new retrofit2.Retrofit.Builder()
                    .baseUrl(BASE_URL)
                    .addConverterFactory(GsonConverterFactory.create())
                    .build();
        }

    }

    public Retrofit getRetrofit(){
        return retrofit;
    }
}

MainActivity.java
package com.example.helloworld;

import androidx.appcompat.app.AppCompatActivity;
import androidx.recyclerview.widget.LinearLayoutManager;
import androidx.recyclerview.widget.RecyclerView;

import android.os.Bundle;
import android.widget.SearchView;
import android.widget.Toast;

import java.util.ArrayList;
import java.util.List;

import retrofit2.Call;
import retrofit2.Callback;
import retrofit2.Response;

public class MainActivity extends AppCompatActivity {

    private RecyclerView recyclerView;
    private SearchView searchView;

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

        SingleTask singleTask = (SingleTask) getApplication();
        UserOperation userOperation = singleTask.getRetrofit().create(UserOperation.class);

        Call<List<User>> mycall = userOperation.getAllUsers();

        mycall.enqueue(new Callback<List<User>>() {
            @Override
            public void onResponse(Call<List<User>> call, Response<List<User>> response) {
                getUserData(response.body());
            }

            @Override
            public void onFailure(Call<List<User>> call, Throwable t) {
                Toast.makeText(MainActivity.this, "There is some problem", Toast.LENGTH_SHORT).
                show();
            }
        });

        initViews();
    }

    private void initViews() {

        recyclerView = findViewById(R.id.myrec);

    }

    private void getUserData(List<User> userList) {

        recyclerView.setLayoutManager(new LinearLayoutManager(this));
        final CustomUserAdapter customStudentAdapter = new CustomUserAdapter(userList);
        recyclerView.setAdapter(customStudentAdapter);

    }

}

UserOperation.java
package com.example.helloworld;

import java.util.List;

import retrofit2.Call;
import retrofit2.http.GET;

public interface UserOperation {

    @GET("/users")
    Call<List<User>> getAllUsers();

}

CustomUserAdapter.java
package com.example.helloworld;

import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.Filter;
import android.widget.Filterable;
import android.widget.TextView;

import androidx.annotation.NonNull;
import androidx.recyclerview.widget.RecyclerView;

import java.util.ArrayList;
import java.util.List;

public class CustomUserAdapter extends RecyclerView.Adapter<CustomUserAdapter.MyView>{
    private List<User> userList;

    public CustomUserAdapter(List<User> userList) {
        this.userList=userList;
    }

    @NonNull
    @Override
    public MyView onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
        View view = LayoutInflater.from(parent.getContext()).inflate(R.layout.item, parent, false);
        return new MyView(view);
    }

    @Override
    public void onBindViewHolder(@NonNull MyView holder, int position) {
        User user = userList.get(position);
        holder.tname.setText(user.getName());
        holder.temail.setText(user.getEmail());
        holder.tcompany.setText(user.getCompany().getName());
        holder.twebsite.setText(user.getWebsite());

    }

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



    class MyView extends RecyclerView.ViewHolder {
        private TextView tcompany, tname, twebsite, temail;

        public MyView(@NonNull View itemView) {
            super(itemView);
            tcompany = itemView.findViewById(R.id.company);
            tname = itemView.findViewById(R.id.name);
            twebsite = itemView.findViewById(R.id.website);
            temail = itemView.findViewById(R.id.email);
        }
    }
}


res/layout/activity_main.xml
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical">


    <androidx.recyclerview.widget.RecyclerView
        android:id="@+id/myrec"
        android:layout_marginRight="20dp"
        android:layout_marginTop="10dp"
        android:layout_marginLeft="20dp"
        android:layout_width="match_parent"
        android:layout_height="match_parent" />


</LinearLayout>


res/layout/item.xml
<?xml version="1.0" encoding="utf-8"?>
<androidx.cardview.widget.CardView xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    app:cardMaxElevation="10dp"
    app:cardUseCompatPadding="true">


    <TableLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:stretchColumns="1">


        <TableRow>

            <TextView
                android:text="Name : "
                android:textStyle="bold" />

            <TextView android:id="@+id/name" />
        </TableRow>

        <TableRow>

            <TextView
                android:text="Email : "
                android:textStyle="bold" />

            <TextView android:id="@+id/email" />
        </TableRow>

        <TableRow>

            <TextView
                android:text="Company : "
                android:textStyle="bold" />

            <TextView android:id="@+id/company" />
        </TableRow>

        <TableRow>

            <TextView
                android:text="Website : "
                android:textStyle="bold" />

            <TextView android:id="@+id/website" />
        </TableRow>
    </TableLayout>


    </androidx.cardview.widget.CardView>

AndroidManifest.xml
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.example.helloworld">

    <uses-permission-sdk-23 android:name="android.permission.INTERNET"/>

    <application
        android:allowBackup="true"
        android:icon="@mipmap/ic_launcher"
        android:name=".SingleTask"
        android:label="@string/app_name"
        android:roundIcon="@mipmap/ic_launcher_round"
        android:supportsRtl="true"
        android:theme="@style/AppTheme">
        <activity android:name=".MainActivity">
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />

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

</manifest>

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