SafeKeyboard/app/src/main/res/layout/keyboard_key_preview_layout.xml

<?xml version="1.0" encoding="utf-8"?>
<TextView xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:background="@drawable/keyboard_enlarge"
    android:gravity="center"
    android:textColor="@color/keyboard_black"
    android:textSize="24sp"
    android:textStyle="bold" />