orhanobut

public class LoginActivity extends Activity implements LoginListener {
  
  @Override
  public void onLogin() {}
  
  @Override
  public void onRegister() {}
  
  @Override
  public void onUsernameTextChanged() {

orhanobut

public class LoginFragment extends Fragment {
  
  ...
  
  public interface LoginListener {
    void onLogin();
    void onRegister();
  
    // new added
    void onUsernameTextChanged();

orhanobut

public class AccountActivity extends Activity implements LoginFragment.LoginListener {

  @Override
  public void onLogin() {
    makeLoginRequest();
  }
  
  @Override
  public void onRegister() {
    makeRegisterRequest();

orhanobut

public class LoginFragment extends Fragment {
  
  private LoginListener loginListener;
  
  //optional
  private TextListener textListener;
  
  public void setTextListener(TextListener listener) {
    this.textListener = listener;
  }

orhanobut

public class LoginActivity extends Activity 
    implements LoginFragment.LoginListener, LoginFragment.TextListener {
  
  public void displayLoginFragment() {
    LoginFragment fragment = LoginFragment.newInstance();
    fragment.setTextListener(this);
    ...
  }
  
  @Override

orhanobut

public class ApiManager implements ApiService {
  
  private final Parser parser = new GsonParser();
  
  @Override
  public void login(Callback callback) {
    ...
    User user = parser.fromBody(body, User.class);
  }
}

orhanobut

public class ApiManager implements ApiService {
  
  private final Parser parser;
  
  public ApiManager(Parser parser) {
    this.parser = parser;
  }
  
  @Override
  public void login(Callback callback) {

orhanobut

public class BaseActivity extends Activity {
  
  ApiService apiService = new ApiManager(new GsonParser());
  
}

orhanobut

public class MyView extends View {
  
  private boolean editMode;
  
  public MyView(Context context, boolean editMode){
    super(context);
    this.editMode = editMode;
  }
  
  @Override

orhanobut

public class MyView extends View {
  
  private boolean editMode;
  
  public MyView(Context context, boolean editMode){
    super(context);
    this.editMode = editMode;
  }
  
  //a new method