app/src/main/res/layout/activity_group_info.xml
<?xml version="1.0" encoding="utf-8"?>
<android.support.constraint.ConstraintLayout 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">
<TextView
android:id="@+id/participantsTextview"
android:layout_width="wrap_content"
android:layout_height="26dp"
android:layout_marginBottom="8dp"
android:layout_marginEnd="8dp"
android:layout_marginStart="16dp"
android:layout_marginTop="16dp"
android:text="Participants"
android:textSize="18sp"
app:layout_constraintBottom_toTopOf="@+id/participantsRecyclerVIew"
app:layout_constraintEnd_toStartOf="@+id/quitGroup"
app:layout_constraintHorizontal_bias="0.0"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent"
app:layout_constraintVertical_bias="1.0" />
<android.support.v7.widget.RecyclerView
android:id="@+id/participantsRecyclerVIew"
android:layout_width="0dp"
android:layout_height="0dp"
android:layout_marginBottom="8dp"
android:layout_marginEnd="8dp"
android:layout_marginStart="8dp"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toBottomOf="@+id/quitGroup" />
<Button
android:id="@+id/quitGroup"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginBottom="2dp"
android:layout_marginEnd="8dp"
android:text="Leave Group"
app:layout_constraintBottom_toTopOf="@+id/participantsRecyclerVIew"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintTop_toTopOf="parent" />
</android.support.constraint.ConstraintLayout>