Post values using retrofit

Question

I am currently new to android . I am using this site for practice: http://dummy.restapiexample.com/, I am trying to use the post request here is the code I am using, I have used jsonschema2pojo and I created two classes so that has confused me, why do we need two classes? and how to use them? The code is not crashing. But , I get null when I display the values in a toast.

JsonPlaceholer.java

public interface JsonPlaceHolderApi {

@FormUrlEncoded
@POST("create")
Call<Post> createPost(@FieldMap Map<String, String> fields);
}

Mainactivity.java

public class MainActivity extends AppCompatActivity {

TextView textViewResult;

private JsonPlaceHolderApi jsonPlaceHolderApi;


@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);


    textViewResult = findViewById(R.id.text_view_result);

    Retrofit retrofit = new Retrofit.Builder()
           // .baseUrl("https://jsonplaceholder.typicode.com/")
            .baseUrl("http://dummy.restapiexample.com/api/v1/")
            .addConverterFactory(GsonConverterFactory.create())
            .build();

    jsonPlaceHolderApi = retrofit.create(JsonPlaceHolderApi.class);

    createPost();
  }

private void createPost() {

    //Post post = new Post(23, "New Title", "New Text");

    Map<String, String> fields = new HashMap<>();
    fields.put("name", "NewName");
    fields.put("salary", "123");
    fields.put("age","12");

    Call<Post> call = jsonPlaceHolderApi.createPost(fields);

    call.enqueue(new Callback<Post>() {
        @Override
        public void onResponse(Call<Post> call, Response<Post> response) {

            if (!response.isSuccessful()) {
                textViewResult.setText("Code: " + response.code());
                return;
            }

            Post postResponse = response.body();

            String content = "";
            content += "Code: " + response.code() + "\n";
            content += "ID: " + postResponse.getId() + "\n";

            content += "Name : " + postResponse.getName() + "\n";
            content += "Salary : " + postResponse.getSalary() + "\n";
            content += "Age :" + postResponse.getAge() + "\n\n";

           // textViewResult2.setText(content);
            Toast.makeText(MainActivity.this, "Ans::"+content, Toast.LENGTH_LONG).show();
        }

        @Override
        public void onFailure(Call<Post> call, Throwable t) {

            //textViewResult.setText(t.getMessage());
            Toast.makeText(MainActivity.this, "Failed "+t.getMessage(), Toast.LENGTH_LONG).show();
        }
    });
}
 }

Post.java

public class Post {

@SerializedName("name")
@Expose
private String name;
@SerializedName("salary")
@Expose
private String salary;
@SerializedName("age")
@Expose
private String age;
@SerializedName("id")
@Expose
private Integer id;

public String getName() {
    return name;
}

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

public String getSalary() {
    return salary;
}

public void setSalary(String salary) {
    this.salary = salary;
}

public String getAge() {
    return age;
}

public void setAge(String age) {
    this.age = age;
}

public Integer getId() {
    return id;
}

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


}

PostR.java

public class PostR {

@SerializedName("status")
@Expose
private String status;
@SerializedName("data")
@Expose
private Post data;

public String getStatus() {
    return status;
}

public void setStatus(String status) {
    this.status = status;
}

public Post getData() {
    return data;
}

public void setData(Post data) {
    this.data = data;
}

}

Answer 1

The 2 classes are for the DTO (data transfer object), mapping the response from the API eith Java objects and mapping the response data with Java objects.

Replace your code with below code, it should work:

Call<PostR> call = jsonPlaceHolderApi.createPost(fields);
    call.enqueue(new Callback<PostR>() {
        @Override
        public void onResponse(Call<PostR> call, Response<PostR> response) {    
            if (!response.isSuccessful()) {
                textViewResult.setText("Code: " + response.code());
                return;
            }    
            PostR postRResponse = response.body();
            Post postResponse = postRResponse.getData();
            if(postResponse!=null) {
                String content = "";
                content += "Code: " + response.code() + "\n";
                content += "ID: " + postResponse.getId() + "\n";    
                content += "Name : " + postResponse.getName() + "\n";
                content += "Salary : " + postResponse.getSalary() + "\n";
                content += "Age :" + postResponse.getAge() + "\n\n";
            }
           // textViewResult2.setText(content);
            Toast.makeText(MainActivity.this, "Ans::"+content, Toast.LENGTH_LONG).show();
        }

        @Override
        public void onFailure(Call<PostR> call, Throwable t) {    
            //textViewResult.setText(t.getMessage());
            Toast.makeText(MainActivity.this, "Failed "+t.getMessage(), Toast.LENGTH_LONG).show();
        }

P.S - General Process you can follow to test API:

1. Check if the Backend (API) is working or not using Postman.
2. Print response.code() and response.body() in Log.
3. Check if the structure (keys/params) of response is same as PostR.java
4. Check if the structure (keys/params) of response.body() is same as Post.java class.
5. If all the above works as expected, your Toast should print correct values.