TRIVIAL DRIVE - SAMPLE FOR IN-APP BILLING VERSION 3
Copyright (c) 2012 Google Inc. All rights reserved.
Bruno Oliveira, 2012-11-29

CHANGELOG

   2012-11-29: initial release
   2013-01-08: updated to include support for subscriptions


WHAT IS THIS SAMPLE?

   This game is a simple "driving" game where the player can buy gas
   and drive. The car has a tank which stores gas. When the player purchases
   gas, the tank fills up (1/4 tank at a time). When the player drives, the gas
   in the tank diminishes (also 1/4 tank at a time).

   The user can also purchase a "premium upgrade" that gives them a red car
   instead of the standard blue one (exciting!).

   The user can also purchase a subscription ("infinite gas") that allows them
   to drive without using up any gas while that subscription is active.


HOW TO RUN THIS SAMPLE

   This sample can't be run as-is. You have to create your own
   application instance in the Developer Console and modify this
   sample to point to it. Here is what you must do:

   ON THE GOOGLE PLAY DEVELOPER CONSOLE
   
   1. Create an application on the Developer Console. You must use
      version 2, available at https://play.google.com/apps/publish/v2/
      or later. In-app billing version 3 is not available in the older
      versions of Developer Console.

   2. In that app, create MANAGED in-app items with these IDs:
          premium, gas
      Set their prices to 1 dollar (or any other price you like,
      but make it a small price since this is just for testing purposes).

   3. In that app, create a SUBSCRIPTION items with this ID:
          infinite_gas
      Set the price to 1 dollar and the billing recurrence to monthly. Just so
      you are not immediately charged when you test it, set the trial period to
      seven days. 

   4. Make sure your test account (the one you will use to test purchases)
      is correctly listed in the "testing" section. Your test account CANNOT
      BE THE SAME AS THE PUBLISHER ACCOUNT. If it is, purchases won't go
      through.

   5. Grab the application's public key (a base-64 string) -- you will need
      that next. Note that this is the *application's* public key, not the
      developer public key. You can find the application's public key in
      the "Services & API" page for your application.

   IN THE CODE

   1. Open MainActivity.java and replace the placeholder key with your app's public key.
   
   2. Change the sample's package name to your package name. To do that, you only need 
   to update the package name in AndroidManifest.xml and correct the references (especially
   the references to the R object).
   
   3. Make sure that AndroidManifest.xml lists the updated package name!
   4. Export an APK, signing it with your PRODUCTION (not debug) developer certificate

   BACK TO GOOGLE PLAY DEVELOPER CONSOLE
   
   1. Upload your APK to Google Play
   2. Wait 2-3 hours for Google Play to process the APK (if you don't, you might
      see errors where Google Play says that "this version of the application
      is not enabled for in-app billing" or something similar)
    
   TEST THE CODE

   1. Install the APK, signed with your PRODUCTION certificate, to a test device [*] 
   2. Run the app
   3. Make purchases (make sure you're purchasing with an account that's NOT
      your developer account with which you uploaded the app to Google Play).

   Remember to refund any real purchases you make, if you don't want the 
   charges to actually to through.

   [*]: it will be easier to use a test device that doesn't have your
   developer account logged in; this is because, if you attempt to purchase
   an in-app item using the same account that you used to publish the app,
   the purchase will not go through.


A NOTE ABOUT SECURITY

   This sample app implements signature verification but does not demonstrate
   how to enforce a tight security model. When releasing a production application 
   to the general public, we highly recommend that you implement the security best
   practices described in our documentation at:
   
   http://developer.android.com/google/play/billing/billing_best_practices.html

   In particular, you should set developer payload strings when making purchase
   requests and you should verify them when reading back the results. This will make
   it more for a malicious party to perform a replay attack on your app.