Android™ How to Program, Second Edition

3.1. Introduction

The Tip Calculator app (Fig. 3.1(a)) calculates and displays possible tips for a restaurant bill. As you enter each digit of a bill amount by touching the numeric keypad, the app calculates and displays the tip amount and total bill (bill amount + tip) for a 15% tip and a custom tip percentage (18% by default). You can specify a custom tip percentage from 0% to 30% by moving the SeekBar thumb—this updates the custom percentage shown and displays the custom tip and total (Fig. 3.1(b)). We chose 18% as the default custom percentage, because many restaurants in the United States add this tip percentage for parties of six people or more. The keypad in Fig. 3.1 may differ based on your AVD’s or device’s Android version, or based ...