Android keyboard focus losts while going to another view by DPAD

Question

We have 17 api, DPAD control and 4 edittexts in one layout for pin enter. When user try to open something which is locked in the app he faced with fragment where he should enter 4 digits pin. When view is opened we set programmatically view focus to the first pins edittext and show keyboard. When user enter first pin digit we set view focus programmatically to second pins edittext where user should enter second pin value and so on.

Issue: After user enter first pin value keyboard focus (highlighted) is disappeared, and for second pin, user should navigate through keyboard from start again. On 21 api the same code works well and keyboard focus (highlighted) stayed on previous value. How to leave keyboard focus (highlighted) when he was before on 17 api while setting view focus on another view?

Here is code:

public class PasswordFragment extends BaseFragment {
    private final ArrayList<Disposable> disposables = new ArrayList<>();
    @BindViews({R.id.passFirst, R.id.passSecond, R.id.passThird, R.id.passFour})
    EditText[] pinEdits;
    @BindDrawable(R.drawable.border_light)
    Drawable borderLight;
    @BindDrawable(R.drawable.border_white)
    Drawable borderWhite;
    @Inject
    PrefsRepo prefsRepo;
    @Inject
    ToastUtil toastUtil;
    @BindView(R.id.passTitle)
    TextView passTitle;
    @BindString(R.string.insert_pin)
    String defDialogMes;
    private InputMethodManager inputMethodManager;



    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        App.getAppComponent().inject(this);
        inputMethodManager = (InputMethodManager) getActivity().getSystemService(Context.INPUT_METHOD_SERVICE);
    }

    @Nullable
    @Override
    public View onCreateView(@NonNull LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
        View v = super.onCreateView(inflater, container, savedInstanceState);
        for (EditText pinEdit : pinEdits) {
            pinEdit.setOnFocusChangeListener((view, hasFocus) -> {
                if (hasFocus) {
                    view.setBackground(borderLight);
                }
            });
        }
        disposables.add(RxTextView.textChanges(pinEdits[0]).subscribe(charSequence -> {
            if (charSequence.length() == 1) {
                pinEdits[1].requestFocus();
            }
        }));
        disposables.add(RxTextView.textChanges(pinEdits[1]).subscribe(charSequence -> {
            if (charSequence.length() == 1) {
                pinEdits[2].requestFocus();
            }
        }));
        disposables.add(RxTextView.textChanges(pinEdits[2]).subscribe(charSequence -> {
            if (charSequence.length() == 1) {
                pinEdits[3].requestFocus();
            }
        }));
        disposables.add(RxTextView.textChanges(pinEdits[3])
                .subscribe(charSequence -> {
                    if (charSequence.length() == 1) {
                        String pin = pinEdits[0].getText().toString() + pinEdits[1].getText().toString() + pinEdits[2].getText().toString() + pinEdits[3].getText().toString();
                        if (pin.length() == 4) {
                              do someting;
                        } else {
                            toastUtil.showToast(getString(R.string.pin_incorrect));
                        }
                    }
                }));
        return v;
    }


    @Override
    public void onResume() {
        clearEditTexts();
        super.onResume();

    }

    private void clearEditTexts() {
        for (EditText pinEdit : pinEdits) {
            pinEdit.getText().clear();
            if (Build.VERSION.SDK_INT <= Build.VERSION_CODES.JELLY_BEAN_MR1){
                pinEdit.setOnClickListener(view -> {
                    showKeyBoard(pinEdit);
                });
            }
        }
        setFocusOnFirst();
    }

    private void setFocusOnFirst() {
        pinEdits[0].setBackground(borderLight);
        pinEdits[0].requestFocus();
        pinEdits[0].postDelayed(() -> {
            showKeyBoard(pinEdits[0]);
        }, 50);
    }


    @Override
    public void onDestroy() {
        super.onDestroy();
        for (Disposable disposable : disposables) {
            disposable.dispose();
        }
    }


    @Override
    protected int getLayoutId() {
        return R.layout.fragment_password;
    }


    private void showKeyBoard(EditText editText){
        inputMethodManager.showSoftInput(editText, InputMethodManager.SHOW_IMPLICIT);
    }
}