build.gradle

      compile 'com.google.code.gson:gson:2.6.2'      compile 'com.squareup.retrofit2:retrofit:2.1.0'// compulsory      compile 'com.squareup.retrofit2:converter-gson:2.1.0' //for retrofit conversion

Login APi Put Two Parameters

    {        "UserId": "1234",        "Password":"1234"    }

Login Response

    {        "UserId": "1234",        "FirstName": "Keshav",        "LastName": "Gera",        "ProfilePicture": "312.113.221.1/GEOMVCAPI/Files/1.500534651736E12p.jpg"    }

APIClient.java

    import retrofit2.Retrofit;    import retrofit2.converter.gson.GsonConverterFactory;    class APIClient {        public static final String BASE_URL = "Your Base Url ";        private static Retrofit retrofit = null;        public static Retrofit getClient() {            if (retrofit == null) {                retrofit = new Retrofit.Builder()                        .baseUrl(BASE_URL)                        .addConverterFactory(GsonConverterFactory.create())                        .build();            }            return retrofit;        }    }

APIInterface interface

    interface APIInterface {        @POST("LoginController/Login")        Call<LoginResponse> createUser(@Body LoginResponse login);    }

Login Pojo

    package pojos;    import com.google.gson.annotations.SerializedName;    public class LoginResponse {        @SerializedName("UserId")        public String UserId;        @SerializedName("FirstName")        public String FirstName;        @SerializedName("LastName")        public String LastName;        @SerializedName("ProfilePicture")        public String ProfilePicture;        @SerializedName("Password")        public String Password;        @SerializedName("ResponseCode")        public String ResponseCode;        @SerializedName("ResponseMessage")        public String ResponseMessage;        public LoginResponse(String UserId, String Password) {            this.UserId = UserId;            this.Password = Password;        }        public String getUserId() {            return UserId;        }        public String getFirstName() {            return FirstName;        }        public String getLastName() {            return LastName;        }        public String getProfilePicture() {            return ProfilePicture;        }        public String getResponseCode() {            return ResponseCode;        }        public String getResponseMessage() {            return ResponseMessage;        }    }

MainActivity

    package com.keshav.retrofitloginexampleworkingkeshav;    import android.app.Dialog;    import android.os.Bundle;    import android.support.v7.app.AppCompatActivity;    import android.util.Log;    import android.view.View;    import android.widget.Button;    import android.widget.EditText;    import android.widget.TextView;    import android.widget.Toast;    import pojos.LoginResponse;    import retrofit2.Call;    import retrofit2.Callback;    import retrofit2.Response;    import utilites.CommonMethod;    public class MainActivity extends AppCompatActivity {        TextView responseText;        APIInterface apiInterface;        Button loginSub;        EditText et_Email;        EditText et_Pass;        private Dialog mDialog;        String userId;        String password;        @Override        protected void onCreate(Bundle savedInstanceState) {            super.onCreate(savedInstanceState);            setContentView(R.layout.activity_main);            apiInterface = APIClient.getClient().create(APIInterface.class);            loginSub = (Button) findViewById(R.id.loginSub);            et_Email = (EditText) findViewById(R.id.edtEmail);            et_Pass = (EditText) findViewById(R.id.edtPass);            loginSub.setOnClickListener(new View.OnClickListener() {                @Override                public void onClick(View v) {                    if (checkValidation()) {                        if (CommonMethod.isNetworkAvailable(MainActivity.this))                            loginRetrofit2Api(userId, password);                        else                            CommonMethod.showAlert("Internet Connectivity Failure", MainActivity.this);                    }                }            });        }        private void loginRetrofit2Api(String userId, String password) {            final LoginResponse login = new LoginResponse(userId, password);            Call<LoginResponse> call1 = apiInterface.createUser(login);            call1.enqueue(new Callback<LoginResponse>() {                @Override                public void onResponse(Call<LoginResponse> call, Response<LoginResponse> response) {                    LoginResponse loginResponse = response.body();                    Log.e("keshav", "loginResponse 1 --> " + loginResponse);                    if (loginResponse != null) {                        Log.e("keshav", "getUserId          -->  " + loginResponse.getUserId());                        Log.e("keshav", "getFirstName       -->  " + loginResponse.getFirstName());                        Log.e("keshav", "getLastName        -->  " + loginResponse.getLastName());                        Log.e("keshav", "getProfilePicture  -->  " + loginResponse.getProfilePicture());                        String responseCode = loginResponse.getResponseCode();                        Log.e("keshav", "getResponseCode  -->  " + loginResponse.getResponseCode());                        Log.e("keshav", "getResponseMessage  -->  " + loginResponse.getResponseMessage());                        if (responseCode != null && responseCode.equals("404")) {                            Toast.makeText(MainActivity.this, "Invalid Login Details \n Please try again", Toast.LENGTH_SHORT).show();                        } else {                            Toast.makeText(MainActivity.this, "Welcome " + loginResponse.getFirstName(), Toast.LENGTH_SHORT).show();                        }                    }                }                @Override                public void onFailure(Call<LoginResponse> call, Throwable t) {                    Toast.makeText(getApplicationContext(), "onFailure called ", Toast.LENGTH_SHORT).show();                    call.cancel();                }            });        }        public boolean checkValidation() {            userId = et_Email.getText().toString();            password = et_Pass.getText().toString();            Log.e("Keshav", "userId is -> " + userId);            Log.e("Keshav", "password is -> " + password);            if (et_Email.getText().toString().trim().equals("")) {                CommonMethod.showAlert("UserId Cannot be left blank", MainActivity.this);                return false;            } else if (et_Pass.getText().toString().trim().equals("")) {                CommonMethod.showAlert("password Cannot be left blank", MainActivity.this);                return false;            }            return true;        }    }

CommonMethod.java

    public class CommonMethod {        public static final String DISPLAY_MESSAGE_ACTION =                "com.codecube.broking.gcm";        public static final String EXTRA_MESSAGE = "message";        public  static boolean isNetworkAvailable(Context ctx) {            ConnectivityManager connectivityManager                    = (ConnectivityManager)ctx.getSystemService(Context.CONNECTIVITY_SERVICE);            NetworkInfo activeNetworkInfo = connectivityManager.getActiveNetworkInfo();            return activeNetworkInfo != null && activeNetworkInfo.isConnected();        }        public static void showAlert(String message, Activity context) {            final AlertDialog.Builder builder = new AlertDialog.Builder(context);            builder.setMessage(message).setCancelable(false)                    .setPositiveButton("OK", new DialogInterface.OnClickListener() {                        public void onClick(DialogInterface dialog, int id) {                        }                    });            try {                builder.show();            } catch (Exception e) {                e.printStackTrace();            }        }    }

activity_main.xml

    <LinearLayout android:layout_width="wrap_content"        android:layout_height="match_parent"        android:focusable="true"        android:focusableInTouchMode="true"        android:orientation="vertical"        xmlns:android="http://schemas.android.com/apk/res/android">            <ImageView                android:id="@+id/imgLogin"                android:layout_width="200dp"                android:layout_height="150dp"                android:layout_gravity="center"                android:layout_marginTop="20dp"                android:padding="5dp"                android:background="@mipmap/ic_launcher_round"                />            <TextView                android:id="@+id/txtLogo"                android:layout_width="wrap_content"                android:layout_height="wrap_content"                android:layout_below="@+id/imgLogin"                android:layout_centerHorizontal="true"                android:text="Holostik Track and Trace"                android:textSize="20dp"                android:visibility="gone" />            <android.support.design.widget.TextInputLayout                android:id="@+id/textInputLayout1"                android:layout_width="fill_parent"                android:layout_height="wrap_content"                android:layout_marginLeft="@dimen/box_layout_margin_left"                android:layout_marginRight="@dimen/box_layout_margin_right"                android:layout_marginTop="8dp"                android:padding="@dimen/text_input_padding">                <EditText                    android:id="@+id/edtEmail"                    android:layout_width="fill_parent"                    android:layout_height="wrap_content"                    android:layout_marginTop="5dp"                    android:ems="10"                    android:fontFamily="sans-serif"                    android:gravity="top"                    android:hint="Login ID"                    android:maxLines="10"                    android:paddingLeft="@dimen/edit_input_padding"                    android:paddingRight="@dimen/edit_input_padding"                    android:paddingTop="@dimen/edit_input_padding"                    android:singleLine="true"></EditText>            </android.support.design.widget.TextInputLayout>            <android.support.design.widget.TextInputLayout                android:id="@+id/textInputLayout2"                android:layout_width="fill_parent"                android:layout_height="wrap_content"                android:layout_below="@+id/textInputLayout1"                android:layout_marginLeft="@dimen/box_layout_margin_left"                android:layout_marginRight="@dimen/box_layout_margin_right"                android:padding="@dimen/text_input_padding">                <EditText                    android:id="@+id/edtPass"                    android:layout_width="match_parent"                    android:layout_height="wrap_content"                    android:focusable="true"                    android:fontFamily="sans-serif"                    android:hint="Password"                    android:inputType="textPassword"                    android:singleLine="true" />            </android.support.design.widget.TextInputLayout>            <RelativeLayout                android:id="@+id/rel12"                android:layout_width="wrap_content"                android:layout_height="wrap_content"                android:layout_below="@+id/textInputLayout2"                android:layout_marginTop="10dp"                android:layout_marginLeft="10dp"                >                <Button                    android:id="@+id/loginSub"                    android:layout_width="wrap_content"                    android:layout_height="45dp"                    android:layout_alignParentRight="true"                    android:layout_centerVertical="true"                    android:background="@drawable/border_button"                    android:paddingLeft="30dp"                    android:paddingRight="30dp"                    android:layout_marginRight="10dp"                    android:text="Login"                    android:textColor="#ffffff" />                </RelativeLayout>    </LinearLayout>

This is a simple solution where we do not need to use JSON

public interface RegisterAPI {@FormUrlEncoded@POST("/RetrofitExample/insert.php")public void insertUser(        @Field("name") String name,        @Field("username") String username,        @Field("password") String password,        @Field("email") String email,        Callback<Response> callback);}

method to send data

private void insertUser(){    //Here we will handle the http request to insert user to mysql db    //Creating a RestAdapter    RestAdapter adapter = new RestAdapter.Builder()            .setEndpoint(ROOT_URL) //Setting the Root URL            .build(); //Finally building the adapter    //Creating object for our interface    RegisterAPI api = adapter.create(RegisterAPI.class);    //Defining the method insertuser of our interface    api.insertUser(            //Passing the values by getting it from editTexts            editTextName.getText().toString(),            editTextUsername.getText().toString(),            editTextPassword.getText().toString(),            editTextEmail.getText().toString(),            //Creating an anonymous callback            new Callback<Response>() {                @Override                public void success(Response result, Response response) {                    //On success we will read the server's output using bufferedreader                    //Creating a bufferedreader object                    BufferedReader reader = null;                    //An string to store output from the server                    String output = "";                    try {                        //Initializing buffered reader                        reader = new BufferedReader(new InputStreamReader(result.getBody().in()));                        //Reading the output in the string                        output = reader.readLine();                    } catch (IOException e) {                        e.printStackTrace();                    }                    //Displaying the output as a toast                    Toast.makeText(MainActivity.this, output, Toast.LENGTH_LONG).show();                }                @Override                public void failure(RetrofitError error) {                    //If any error occured displaying the error as toast                    Toast.makeText(MainActivity.this, error.toString(),Toast.LENGTH_LONG).show();                }            }    );}

Now we can get the post request using php aur any other server side scripting.

Source Android Retrofit Tutorial

I have found the solution. The issue was a problem in my classes structure. So i updated them like the following samples.

public class LandingPageReport {    private ArrayList<LandingPageReportItem> GetDetailWithMonthWithCodeResult;    // + Getter Setter methods}public class LandingPageReportItem {    private String code;    private String field1;    // + Getter Setter methods}

And then i use this retrofit configuration

@POST("/GetDetailWithMonthWithCode")void getLandingPageReport(@Field("code") String code,                          @Field("monthact") String monthact,                          Callback<LandingPageReport> cb);