@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_login);

    user = (EditText) findViewById(R.id.username);
    password = (EditText) findViewById(R.id.senha);

    salvar = (Button) findViewById(R.id.salvar);
    salvar.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view) {
            SharedPreferences settings = getSharedPreferences(PREFS_USER, 0);
            SharedPreferences.Editor editor = settings.edit();
            editor.putString("PrefUser", user.getText().toString());
            editor.putString("PrefPass", password.getText().toString());

            //Confirma a gravação dos dados
            editor.commit();

            loadJson(user.getText().toString());

        }
    });

    SharedPreferences settings = getSharedPreferences(PREFS_USER, 0);
    user.setText(settings.getString("PrefUser", ""));
    password.setText(settings.getString("PrefPass", ""));
}

public void loadJson(String usuario){

    Retrofit.Builder builder = new Retrofit.Builder()
            .baseUrl("http://"+getSharedPreferences(PREFS_NAME, Context.MODE_PRIVATE).getString("PrefHost", "") +":8080/FazendaWebservice/webresources/fazenda/")
            .addConverterFactory(GsonConverterFactory.create());

    Retrofit retrofit = builder.build();

    AcessoClient client = retrofit.create(AcessoClient.class);
    Call<Acesso> call = client.reposForUsuario(usuario);

    call.enqueue(new Callback<Acesso>() {
        @Override
        public void onResponse(Call<Acesso> call, Response<Acesso> response) {
            String userid = user.getText().toString();
            if(userid.trim().equals("admin")){
                Intent passou = new Intent(LoginActivity.this, BuscaActivity.class);
                startActivity(passou);
            }else{
                Toast.makeText(LoginActivity.this, "Usuário incorreto", Toast.LENGTH_SHORT).show();
            }
        }

        @Override
        public void onFailure(Call<Acesso> call, Throwable t) {
            Toast.makeText(LoginActivity.this, "         Erro ao estabelecer conexão"+ "n"+"            Verifique o host inserido"+"n"+"Por favor tente novamente mais tarde!", Toast.LENGTH_SHORT).show();
        }
    });
}