crystal-wallet-android/app/src/main/res/layout/fragment_pin_security.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/tvCurrentPin"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="@string/current_pin"
        app:layout_constraintBottom_toTopOf="@+id/etCurrentPin"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent"
        app:layout_constraintVertical_chainStyle="packed" />

    <EditText
        android:id="@+id/etCurrentPin"
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:inputType="numberPassword"
        app:layout_constraintBottom_toTopOf="@+id/etNewPin"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintHorizontal_bias="0.5"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/tvCurrentPin"
        tools:ignore="LabelFor" />

    <EditText
        android:id="@+id/etNewPin"
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:layout_marginTop="16dp"
        android:hint="@string/new_pin"
        android:inputType="numberPassword"
        app:layout_constraintBottom_toTopOf="@+id/etConfirmPin"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintHorizontal_bias="0.5"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/etCurrentPin" />

    <EditText
        android:id="@+id/etConfirmPin"
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:layout_marginTop="16dp"
        android:hint="@string/confirm_pin"
        android:inputType="numberPassword"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintHorizontal_bias="0.5"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/etNewPin" />

</android.support.constraint.ConstraintLayout>