Can I put a Button to bottom of a ConstraintLayout inside ScrollView?

Question

I have a ScrollView contains a ConstraintLayout. Inside the ConstraintLayout, I put many views with an attribute layout_constraintTop_toBottomOf to make a relation between the view and the view top of it, and I used layout_marginTop to put spaces between the views.

In my design, I have a Button that should be in the bottom of the layout and it cannot happen with the layout_marginTop because it should have a relation with the bottom of the ConstraintLayout.

Here's my code:

<ScrollView xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    android:layout_width="match_parent"
    android:layout_height="match_parent">

    <android.support.constraint.ConstraintLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:paddingTop="10dp"
        android:paddingBottom="10dp">

        <TextView
            android:id="@+id/logo"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_centerInParent="true"
            android:layout_margin="120dp"
            android:text="Logo"
            app:layout_constraintLeft_toLeftOf="parent"
            app:layout_constraintRight_toRightOf="parent"
            app:layout_constraintTop_toTopOf="parent" />

        <EditText
            android:id="@+id/un_et"
            android:layout_width="match_parent"
            android:layout_height="50dp"
            android:layout_marginLeft="28dp"
            android:layout_marginTop="25dp"
            android:layout_marginRight="28dp"
            android:gravity="center"
            android:hint="User name"
            android:textColor="#bebebe"
            android:textCursorDrawable="@null"
            app:layout_constraintLeft_toLeftOf="parent"
            app:layout_constraintRight_toRightOf="parent"
            app:layout_constraintTop_toBottomOf="@id/logo" />


        <EditText
            android:id="@+id/pw_et"
            android:layout_width="match_parent"
            android:layout_height="50dp"
            android:layout_marginLeft="28dp"
            android:layout_marginTop="13dp"
            android:layout_marginRight="28dp"
            android:gravity="center"
            android:hint="Password"
            android:inputType="textPassword"
            android:textColor="#bebebe"
            android:textCursorDrawable="@null"
            app:layout_constraintLeft_toLeftOf="parent"
            app:layout_constraintRight_toRightOf="parent"
            app:layout_constraintTop_toBottomOf="@id/un_et" />

        <RelativeLayout
            android:id="@+id/save_pw"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:layout_marginTop="8dp"
            android:paddingLeft="28dp"
            android:paddingRight="28dp"
            app:layout_constraintTop_toBottomOf="@id/pw_et">

            <CheckBox
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:layout_centerVertical="true"
                android:buttonTint="#bebebe"
                android:text="Save account"
                android:textColor="#bebebe" />

            <TextView
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:layout_alignParentRight="true"
                android:layout_centerVertical="true"
                android:text="Forget password?"
                android:textColor="#a40000" />
        </RelativeLayout>


        <Button
            android:id="@+id/btn"
            android:layout_width="match_parent"
            android:layout_height="50dp"
            android:layout_marginLeft="28dp"
            android:layout_marginTop="17dp"
            android:layout_marginRight="28dp"
            android:text="Login"
            android:textAllCaps="false"
            android:textColor="#FFFFFF"
            app:layout_constraintTop_toBottomOf="@id/save_pw" />

        <Button
            android:id="@+id/btn2"
            android:layout_width="match_parent"
            android:layout_height="50dp"
            android:text="Sign up"
            android:textAllCaps="false"
            android:textColor="#FFFFFF"
            app:layout_constraintTop_toBottomOf="@id/btn" />
    </android.support.constraint.ConstraintLayout>
</ScrollView>

Answer 1

Replace ScrollView with NestedScrollView & also add android:fillViewport="true" like this

    <androidx.core.widget.NestedScrollView
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:fillViewport="true">

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

            // rest of code

            <Button
                android:id="@+id/btn2"
                android:layout_width="match_parent"
                android:layout_height="50dp"
                android:text="Sign up"
                android:textAllCaps="false"
                android:textColor="#FFFFFF"
                app:layout_constraintVertical_bias="1"
                app:layout_constraintTop_toBottomOf="@id/btn" 
                app:layout_constraintBottom_toBottomOf="parent"/>

        </androidx.constraintlayout.widget.ConstraintLayout>

    </androidx.core.widget.NestedScrollView>

Answer 2

Just set this property to your button:

app:layout_constraintBottom_toBottomOf="parent"

Then add this to your last view this property:

app:layout_constraintBottom_toTopOf="@+id/button"

Also, add to your last view:

android:layout_marginBottom="height_of_button"

However, if you are adding a lot of views it would be better to populate them inside a RecyclerView using an Adapter. Decide what you want to do. Also, tell me if I understood your question correctly, it was a bit confusing.