4.1. Introduction

The Tip Calculator app (Fig. 4.1) calculates and displays tips for a restaurant bill. As the user enters a bill total, the app calculates and displays the tip amount and total bill for three common tipping percentages—10%, 15% and 20%. The user can also specify a custom tip percentage by moving the thumb of a Seekbar—this updates the percentage shown to the right of the Seekbar. We chose 18% as the default custom percentage in this app because many restaurants add this tip percentage for parties of six people or more. The suggested tips and bill totals are updated in response to each user interaction. [Note: The keypad in Fig. 4.1 may differ based on your AVD’s or device’s Android version.]

Fig. 4.1. Entering the bill total and calculating the tip.