Retrofit example

Frontend/app/src/main/java/com/example/mobileapp/Start_Screen.java

@@ -3,23 +3,31 @@ package com.example.mobileapp;
 import androidx.appcompat.app.AppCompatActivity;
 import android.content.Intent;
 import android.os.Bundle;
+import android.util.Log;
 import android.view.View;
 import android.widget.Toast;
 
+import com.example.mobileapp.model.User;
+import com.example.mobileapp.networking.RetrofitClient;
+import com.example.mobileapp.networking.UserService;
 import com.google.android.material.textfield.TextInputLayout;
 
+import retrofit2.Call;
+import retrofit2.Callback;
+import retrofit2.Response;
+
 public class Start_Screen extends AppCompatActivity {
 
     private TextInputLayout textInputEmail;
     private TextInputLayout textInputPW;
-
+    private UserService userService;
 
 
     @Override
     protected void onCreate(Bundle savedInstanceState) {
         super.onCreate(savedInstanceState);
         setContentView(R.layout.activity_main);
-
+        userService = RetrofitClient.getRetrofitInstance().create(UserService.class);
         textInputEmail = findViewById(R.id.text_input_email);
         textInputPW = findViewById(R.id.text_input_pw);
 
@@ -27,7 +35,6 @@ public class Start_Screen extends AppCompatActivity {
 
         private boolean validateEmail () {
             String emailInput = textInputEmail.getEditText().getText().toString().trim();
-
             if(emailInput.isEmpty()) {
                 textInputEmail.setError("Field cannot be empty");
                 return false;
@@ -66,6 +73,20 @@ public class Start_Screen extends AppCompatActivity {
             }
             startActivity(new Intent(Start_Screen.this, Trip_Overview_Screen.class));
             Toast.makeText(this, "Logging in ...", Toast.LENGTH_SHORT).show();
+            final User[] testUser = new User[0];
+            Call<User> call = userService.getUserByEmail("bruno@mail.com");
+            call.enqueue(new Callback<User>() {
+                @Override
+                public void onResponse(Call<User> call, Response<User> response) {
+                    // https://medium.com/@prakash_pun/retrofit-a-simple-android-tutorial-48437e4e5a23
+                    testUser[0] = response.body();
+                }
+
+                @Override
+                public void onFailure(Call<User> call, Throwable t) {
+                    //onFailure
+                }
+            });
         }
 
     /**