Ejemplo de Android + Firebase parte 2

activity_main2.xml

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:paddingBottom="@dimen/activity_vertical_margin"
    android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin"
    tools:context=".activities.Main2Activity">

    <EditText
        android:id="@+id/editText2"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_alignParentTop="true"
        android:layout_centerHorizontal="true"
        android:hint="@string/edit_text_hint_2" />

    <Button
        android:id="@+id/button2"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="@string/button_label"
        android:layout_below="@id/editText2"
        android:layout_centerHorizontal="true"  />

    <TextView
        android:id="@+id/textView3"
        android:layout_marginTop="@dimen/activity_vertical_margin"
        android:layout_below="@id/button2"
        android:text="@string/text_view_label_2"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content" />
    <TextView
        android:id="@+id/textView4"
        android:layout_marginTop="@dimen/activity_vertical_margin"
        android:text="@string/text_view_initial_2"
        android:textSize="20sp"
        android:layout_below="@id/textView3"
        android:layout_centerHorizontal="true"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content" />
</RelativeLayout>