the softkeyboard makes view disappear when it pops up

Question

I have this situation

when i get the focus on the inputText, therefore triggering the softkeyboard to show up, the second text and the second button disappear.

I tried to examine with the debbugger, the associated object are still there, so i though they were just invisibile, so i modified thier visibility but the result stays the same.

in other activities i've never had this problem when softkeyboard showed up. what's new is that in this one i'm using a viewpageadapter, and this screen is one of it's fragment.

Considering that I MUSTN'T remove the viewpageadapter, how can I made the last two views visibile?

As of now, i haven't associated code to them 'cause... for now they are invisibile and so inaccessibile

here is the current code of this fragment:

public class TabComb extends Fragment {

private EditText input;
private TextView outCon, outCov;
private Button getCon, getCov;

@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
                         Bundle savedInstanceState) {

    View root = inflater.inflate(R.layout.fragment_tab_comb, container, false);

    input = root.findViewById(R.id.input_lineare);
    outCon = root.findViewById(R.id.output_conica);
    outCov = root.findViewById(R.id.output_convessa);
    getCon = root.findViewById(R.id.getConica);
    getCov = root.findViewById(R.id.getConvessa);

    getCon.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {

            String scalare = String.valueOf(input.getText());
            Scalare S = new Scalare();
            //TODO convertire input testo in vettore
            //outCon.setText(S.MatrixToString(S.getConica(scalare)));
        }
    });

    outCov.setVisibility(View.VISIBLE);
    getCov.setVisibility(View.VISIBLE);

    return root;
}

and there is the .xml

<?xml version="1.0" encoding="utf-8"?>
<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".ui.combinazioni.TabComb">

    <androidx.constraintlayout.widget.ConstraintLayout
        android:layout_width="match_parent"
        android:layout_height="match_parent">

        <EditText
            android:id="@+id/input_lineare"
            android:layout_width="250dp"
            android:layout_height="wrap_content"
            android:layout_marginStart="50dp"
            android:layout_marginTop="32dp"
            android:hint="@string/lin_input"
            android:inputType="text"
            android:minHeight="50dp"
            app:layout_constraintStart_toStartOf="parent"
            app:layout_constraintTop_toTopOf="parent"
            android:autofillHints="" />

        <TextView
            android:id="@+id/output_conica"
            android:layout_width="260dp"
            android:layout_height="35dp"
            android:layout_marginTop="80dp"
            android:hint="@string/conica_output"
            app:layout_constraintStart_toStartOf="@+id/input_lineare"
            app:layout_constraintTop_toBottomOf="@+id/input_lineare" />

        <TextView
            android:id="@+id/output_convessa"
            android:layout_width="260dp"
            android:layout_height="39dp"
            android:layout_marginTop="90dp"
            android:hint="@string/convessa_output"
            android:visibility="visible"
            app:layout_constraintStart_toStartOf="@+id/output_conica"
            app:layout_constraintTop_toBottomOf="@+id/output_conica"
            tools:visibility="visible" />

        <Button
            android:id="@+id/getConica"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_marginTop="16dp"
            android:text="@string/conica_butt"
            android:textColor="#FFFFFF"
            android:visibility="visible"
            app:layout_constraintStart_toStartOf="@+id/output_conica"
            app:layout_constraintTop_toBottomOf="@+id/output_conica"
            tools:ignore="TextContrastCheck"
            tools:visibility="visible" />

        <Button
            android:id="@+id/getConvessa"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_marginTop="16dp"
            android:text="@string/convessa_butt"
            android:textColor="#FFFFFF"
            android:visibility="visible"
            app:layout_constraintStart_toStartOf="@+id/output_convessa"
            app:layout_constraintTop_toBottomOf="@+id/output_convessa"
            tools:ignore="TextContrastCheck"
            tools:visibility="visible" />
    </androidx.constraintlayout.widget.ConstraintLayout>

</FrameLayout>

What do i have to change?

should i have to "rebuild" everytime the inputText lost it's focus??