How to Post Data to API using Retrofit in Android?

We have seen reading data from API in our Android app in Android Studio. For reading data from API, we use GET request to read our data which is in JSON format. In this article, we will take a look at adding data to REST API in our Android App in Android Studio. 

What we are going to build in this article? 

We will be building a simple application in which we will be adding data to our REST API using the Retrofit library with POST Request. We will add the data through edit text fields and we will verify through response code that our data has been added to the API or not. When we added data to our API we will get to see 201 as a response code. 201 response code means data has been added to our API. A sample video is given below to get an idea about what we are going to do in this article. Note that we are going to implement this project using the Java language. 

Data can be added to API in different formats such as XML Form and JSON. Most of the APIs post their data in JSON format. So we will also be posting our data to our API in the form of the JSON object.

Step by Step Implementation

Step 1: Create a New Project

To create a new project in Android Studio please refer to How to Create/Start a New Project in Android Studio. Note that select Java as the programming language.

Step 2: Add the below dependency in your build.gradle file

Navigate to the Gradle Scripts > build.gradle(Module:app) and add the below dependency in the dependencies section.   

// below dependency for using the retrofit

implementation 'com.squareup.retrofit2:retrofit:2.9.0'

implementation 'com.squareup.retrofit2:converter-gson:2.5.0'

After adding this dependency sync your project and now move towards the AndroidManifest.xml part.  

Step 3: Adding permissions to the internet in the AndroidManifest.xml file

Navigate to the app > AndroidManifest.xml and add the below code to it. 

Step 4: Working with the activity_main.xml file

Navigate to the app > res > layout > activity_main.xml and add the below code to that file. Below is the code for the activity_main.xml file. 

Step 5: Creating a modal class for storing our data  

Navigate to the app > java > your app's package name > Right-click on it > New > Java class and name it as DataModal and add the below code to it. Comments are added inside the code to understand the code in more detail.

Step 6: Creating an Interface class for our API Call

Navigate to the app > java > your app’s package name > Right-click on it > New > Java class select it as Interface and name the file as RetrofitAPI and add below code to it. Comments are added inside the code to understand the code in more detail.

Step 7: Working with theMainActivity.java file

Go to the MainActivity.java file and refer to the following code. Below is the code for the MainActivity.java file. Comments are added inside the code to understand the code in more detail.

Now run your app and see the output of the app. 

Output: