Retrofit Tutorial SIMPLE GET REQUEST - Android Studio

Retrofit

Make sure to require Internet permissions in your AndroidManifest.xml file:

<manifest xmlns:android="http://schemas.android.com/apk/res/android">
    <uses-permission android:name="android.permission.INTERNET" />
</manifest>

Add the following to your app/build.gradle file:

dependencies {
    implementation 'com.google.code.gson:gson:2.8.5'
    implementation 'com.squareup.retrofit2:retrofit:2.4.0'
    implementation 'com.squareup.retrofit2:converter-gson:2.4.0'  

}

	<?xml version="1.0" encoding="utf-8"?>
	<RelativeLayout 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=".MainActivity">
	<androidx.recyclerview.widget.RecyclerView
	android:id="@+id/recycler"
	android:layout_width="match_parent"
	android:layout_height="wrap_content" />
	</RelativeLayout>

view raw activity_main.xml hosted with ❤ by GitHub

	<?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"
	android:layout_margin="8dp"
	android:orientation="vertical"
	app:cardCornerRadius="8dp"
	app:cardElevation="6dp">
	<LinearLayout
	android:layout_width="match_parent"
	android:layout_height="wrap_content"
	android:layout_margin="8dp"
	android:orientation="vertical">
	<TextView
	android:id="@+id/title"
	android:layout_width="match_parent"
	android:layout_height="wrap_content"
	android:text="@string/app_name"
	android:textColor="#000"
	android:textSize="16sp" />
	<TextView
	android:id="@+id/body"
	android:layout_width="match_parent"
	android:layout_height="wrap_content"
	android:text="@string/app_name"
	android:textColor="#000"
	android:textSize="13sp" />
	</LinearLayout>
	</androidx.cardview.widget.CardView>

view raw item.xml hosted with ❤ by GitHub

	package com.csdevbin.retrofitdemo;
	import java.util.List;
	import retrofit2.Call;
	import retrofit2.http.GET;
	public interface JsonPlaceHolderApi {
	@GET("posts")
	Call<List<Post>> getPosts();
	}

view raw JsonPlaceHolderApi.java hosted with ❤ by GitHub

	package com.csdevbin.retrofitdemo;
	import androidx.appcompat.app.AppCompatActivity;
	import androidx.recyclerview.widget.DefaultItemAnimator;
	import androidx.recyclerview.widget.LinearLayoutManager;
	import androidx.recyclerview.widget.RecyclerView;
	import android.os.Bundle;
	import java.util.List;
	import retrofit2.Call;
	import retrofit2.Callback;
	import retrofit2.Response;
	import retrofit2.Retrofit;
	import retrofit2.converter.gson.GsonConverterFactory;
	public class MainActivity extends AppCompatActivity {
	private String BASE_URL = "https://jsonplaceholder.typicode.com/";
	private RecyclerAdapter adapter;
	private RecyclerView mRecyclerView;
	private LinearLayoutManager manager;
	@Override
	protected void onCreate(Bundle savedInstanceState) {
	super.onCreate(savedInstanceState);
	setContentView(R.layout.activity_main);
	// mRecyclerView.setAdapter(mAdapter);
	retroCall();
	}
	private void retroCall() {
	Retrofit retrofit = new Retrofit.Builder()
	.baseUrl(BASE_URL)
	.addConverterFactory(GsonConverterFactory.create())
	.build();
	JsonPlaceHolderApi jsonPlaceHolderApi = retrofit.create(JsonPlaceHolderApi.class);
	Call<List<Post>> call = jsonPlaceHolderApi.getPosts();
	call.enqueue(new Callback<List<Post>>() {
	@Override
	public void onResponse(Call<List<Post>> call, Response<List<Post>> response) {
	/*if (!response.isSuccessful()) {
	}*/
	List<Post> posts = response.body();
	mRecyclerView = findViewById(R.id.recycler);
	manager = new LinearLayoutManager(MainActivity.this);
	mRecyclerView.setLayoutManager(manager);
	mRecyclerView.setHasFixedSize(true);
	adapter = new RecyclerAdapter(posts);
	mRecyclerView.setAdapter(adapter);
	}
	@Override
	public void onFailure(Call<List<Post>> call, Throwable t) {
	}
	});
	}
	}

view raw MainActivity.java hosted with ❤ by GitHub

	package com.csdevbin.retrofitdemo;
	import com.google.gson.annotations.SerializedName;
	public class Post {
	private int userId;
	private int id;
	private String title;
	@SerializedName("body")
	private String text;
	public int getUserId() {
	return userId;
	}
	public int getId() {
	return id;
	}
	public String getTitle() {
	return title;
	}
	public String getText() {
	return text;
	}
	}

view raw Post.java hosted with ❤ by GitHub

	package com.csdevbin.retrofitdemo;
	import android.view.LayoutInflater;
	import android.view.View;
	import android.view.ViewGroup;
	import android.widget.TextView;
	import androidx.annotation.NonNull;
	import androidx.recyclerview.widget.RecyclerView;
	import java.util.List;
	public class RecyclerAdapter extends RecyclerView.Adapter<RecyclerAdapter.MyHolder> {
	List<Post> postList;
	public RecyclerAdapter(List<Post> postList) {
	this.postList = postList;
	}
	@NonNull
	@Override
	public MyHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
	View view = LayoutInflater.from(parent.getContext())
	.inflate(R.layout.item, parent, false);
	return new MyHolder(view);
	}
	@Override
	public void onBindViewHolder(@NonNull MyHolder holder, int position) {
	Post post = postList.get(position);
	holder.title.setText(post.getTitle());
	holder.body.setText(post.getText());
	}
	@Override
	public int getItemCount() {
	return postList.size();
	}
	public class MyHolder extends RecyclerView.ViewHolder {
	public TextView title;
	public TextView body;
	public MyHolder(@NonNull View view) {
	super(view);
	title = view.findViewById(R.id.title);
	body = view.findViewById(R.id.body);
	}
	}
	}

view raw RecyclerAdapter.java hosted with ❤ by GitHub