How to fix a view from going off of a page when it is constrained to a card view
I'm not so sure about android x but the constraint layouts are used for removing the nested layouts so, you should not be using constraint layout inside card view. Try this code as a reference. It might help.
<?xml version="1.0" encoding="utf-8"?>
<android.support.constraint.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
xmlns:app="http://schemas.android.com/apk/res-auto">
<android.support.v7.widget.CardView
android:id="@+id/cv_text"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_margin="8dp"
app:layout_constraintTop_toTopOf="parent"
app:layout_constraintTop_toBottomOf="parent">
<TextView
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_marginStart="16dp"
android:layout_marginTop="16dp"
android:layout_marginEnd="16dp"
android:layout_marginBottom="16dp"
android:text="Text View Test"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent" />
</android.support.v7.widget.CardView>
<Button
android:id="@+id/materialButton"
android:layout_width="0dp"
android:layout_height="wrap_content"
android:layout_marginStart="8dp"
android:layout_marginTop="280dp"
android:layout_marginEnd="8dp"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintHorizontal_bias="0.0"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toBottomOf="@+id/cv_text" />
</android.support.constraint.ConstraintLayout>
Your layout is getting pushed because of this line:
android:layout_marginBottom="256dp"
Different phones got different screen size, in your layout you are using fixed size on your view ("256dp") and it makes your layout non-responsive.
So what may look good on your preview may not look the same on a real phone.
If you want to place some view anywhere on your screen and keep it responsive I recommend using guidelines, something like this:
<androidx.constraintlayout.widget.ConstraintLayout
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">
<androidx.cardview.widget.CardView
android:id="@+id/cv_text"
android:layout_width="0dp"
android:layout_height="0dp"
android:layout_margin="8dp"
android:layout_marginStart="8dp"
android:layout_marginLeft="8dp"
android:layout_marginBottom="8dp"
app:layout_constraintBottom_toTopOf="@+id/materialButton"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toBottomOf="parent"
app:layout_constraintTop_toTopOf="parent">
<TextView
android:layout_width="match_parent"
android:layout_height="match_parent"
android:text="Text View Test"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent" />
</androidx.cardview.widget.CardView>
<Button
android:id="@+id/materialButton"
android:layout_width="0dp"
android:layout_height="wrap_content"
android:layout_marginStart="8dp"
android:layout_marginEnd="8dp"
android:layout_marginBottom="8dp"
app:layout_constraintBottom_toTopOf="@+id/guideline13"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent" />
<androidx.constraintlayout.widget.Guideline
android:id="@+id/guideline13"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:orientation="horizontal"
app:layout_constraintGuide_percent=".5" />
</androidx.constraintlayout.widget.ConstraintLayout>
And it will look like this: