@Override
    public void onActivityCreated(@Nullable Bundle savedInstanceState) {
        super.onActivityCreated(savedInstanceState);

        if (getView() != null) {
            getView().setFocusableInTouchMode(true);
            getView().requestFocus();
            getView().setOnKeyListener(new View.OnKeyListener() {
                @Override
                public boolean onKey(View v, int keyCode, KeyEvent event) {
                    if (event.getAction() == KeyEvent.ACTION_DOWN) {
                        if (keyCode == KeyEvent.KEYCODE_BACK) {
                             // Here Write code for transfer fragment.
                             ChangeCurrentFragment(new FragmentC);
                            return true;
                        }
                    }
                    return false;
                }
            });
        }
    }

private void ChangeCurrentFragment(Fragment fragment) {
        //hideKeyBoard();
        FragmentManager fManager = getSupportFragmentManager();
        FragmentTransaction fTransaction = fManager.beginTransaction();
        fTransaction.setCustomAnimations(R.anim.fragment_enter_anim, R.anim.fragment_exit_anim);
        fTransaction.replace(R.id.layoutFHostFragment, fragment, fragment.getClass().getName());
        fTransaction.commitAllowingStateLoss();
    }

@Override
        public void onActivityCreated(@Nullable Bundle savedInstanceState) {
            super.onActivityCreated(savedInstanceState);

            if (getView() != null) {
                getView().setFocusableInTouchMode(true);
                getView().requestFocus();
                getView().setOnKeyListener(new View.OnKeyListener() {
                    @Override
                    public boolean onKey(View v, int keyCode, KeyEvent event) {
                        if (event.getAction() == KeyEvent.ACTION_DOWN) {
                            if (keyCode == KeyEvent.KEYCODE_BACK) {
                                 // Here Write code for transfer fragment.
                                 ChangeCurrentFragment(new FragmentB);
                                return true;
                            }
                        }
                        return false;
                    }
                });
            }
        }