core/res/res/layout/keyboard_key_preview.xml

<?xml version="1.0" encoding="utf-8"?>
<!--
/* 
**
** Copyright 2008, The Android Open Source Project
**
** Licensed under the Apache License, Version 2.0 (the "License"); 
** you may not use this file except in compliance with the License. 
** You may obtain a copy of the License at 
**
**     http://www.apache.org/licenses/LICENSE-2.0 
**
** Unless required by applicable law or agreed to in writing, software 
** distributed under the License is distributed on an "AS IS" BASIS, 
** WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 
** See the License for the specific language governing permissions and 
** limitations under the License.
*/
-->

<TextView xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="wrap_content" 
    android:layout_height="80sp"
    android:textSize="40sp"
    android:textColor="?android:attr/textColorPrimaryInverse"
    android:minWidth="32dip"
    android:gravity="center"
    android:background="@drawable/keyboard_key_feedback"
    />