session-android/res/layout/registration_welcome_activity.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/textView"
        style="@style/Signal.Text.Headline.Registration"
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:layout_marginStart="32dp"
        android:layout_marginTop="32dp"
        android:layout_marginEnd="32dp"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        android:textAlignment="center"
        android:text="@string/activity_landing_title" />

    <TextView
        android:id="@+id/welcome_terms_button"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginBottom="24dp"
        style="@style/Signal.Text.Body"
        android:text="@string/activity_landing_privacy_policy_button_title"
        android:textColor="@color/signal_primary"
        app:layout_constraintBottom_toTopOf="@+id/welcome_continue_button"
        app:layout_constraintEnd_toEndOf="@+id/welcome_continue_button"
        app:layout_constraintStart_toStartOf="@+id/welcome_continue_button" />

    <com.dd.CircularProgressButton
        android:id="@+id/welcome_continue_button"
        android:layout_width="0dp"
        android:layout_height="50dp"
        android:layout_gravity="center_horizontal"
        android:layout_marginStart="32dp"
        android:layout_marginEnd="32dp"
        android:layout_marginBottom="54dp"
        android:background="@color/signal_primary"
        android:textColor="@color/white"
        android:elevation="4dp"
        app:cpb_colorIndicator="@color/white"
        app:cpb_colorProgress="@color/textsecure_primary"
        app:cpb_cornerRadius="4dp"
        app:cpb_selectorIdle="@drawable/progress_button_state"
        app:cpb_textIdle="@string/RegistrationActivity_continue"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent" />

</android.support.constraint.ConstraintLayout>