通过Google Play购买的按设备订购

Question

I would like to setup subscription based billing for an app that will be sold through Google Play. Is it possible to sell the same subscription to the same user but on a different devices? So that every device that user tries to use the app on would need an active subscription?

I was thinking I could store the device id and user id on my own server and authenticate it that way, but is it correct that a user can't purchase the same subscription more than once? So would I need a pool of basically the same subscriptions if the user wishes to purchase multiple "licenses"? Can Google Play Billing handle any of this natively?

Thanks

Answer 1

The documentation from Google initially seems to make this impossible to achieve but digging deeper, I uncovered the following...

In the Google Play API version 2.0, you could create what was called an "unmanaged" product type that allowed the user to purchase the same thing multiple times. That seems to have partly disappeared in API 3.0 although the Gooogle Developer Console clearly supports this. I assume it's still supported because apps that used the 2.0 API are still out there and Google just can't drop support for that.

In 3.0 however, the "unmanaged" product type is not listed in the API docs but the docs state the following about making multiple purchases for the same product type (one-time purchase or subscription):

If you are using the Version 3 API, you can also consume managed items within your application. You would typically implement consumption for items that can be purchased multiple times (such as in-game currency, fuel, or magic spells). Once purchased, a managed item cannot be purchased again until you consume the item, by sending a consumption request to Google Play. To learn more about in-app product consumption, see Consuming Items

http://developer.android.com/google/play/billing/api.html#consume

IMPORTANT: Subscriptions CANNOT be consumed which means that if you want the customer to periodically renew their license, you will have to contact them and tell them that they must purchase the license again. That's a downside if your service requires a periodic renewal.

To obtain what you are after, you will need a backend server to handle the registration of devices and store tokens the apps receive from Google Play when purchasing. When a user wants to purchase your license, feature, service (or whatever) from another device, the other device MUST first release its "ownership" of the product with Google Play, through a process known as "consuming". It would work something more or less like this:

1. The first device makes a purchase and receives a purchaseToken string from Google Play.
2. The purchaseToken along with the device ID is sent from the app to your server and stored.
3. The user goes to the second device and wants to purchase the license as well for that device. The app first needs to go to your server and obtain the purchaseToken (that the first device uploaded) and then call Google Play with consumePurchase which releases the "ownership" of the product from the user.
4. The app then purchases the new license (or whatever) from Google Play, gets a new purchaseToken and stores it on your server along with its device ID.

In essence, Google Play won't keep track of which device has the product. It only associates the Google Account with the product being purchased. It's up to your app and server to manage the licenses.

There is one potential problem I see that you need to address. If for some reason the app fails to send the purchaseToken back to your server (your server is down, the user dropped their device and broke it, your app crashes before it saves the token on the device, etc.), then you may not know if the user paid for the service. Google does provide a server API that lets your backend server query Google Play on Google's server for information about purchases, but I'm not familiar with it nor its limitations.

Answer 2

You will need to implement in app purchases as you would for any other in app item.

Make sure when you create your item in the Dev Console, it is unmanaged, as managed items can only be purchased once per account.

When you receive a confirmation on purchase of your unmanaged item, send the details like the unique ID to your server and store them there.

Now whenever your app starts, check with your server if it is an authorized device. If it isn't, prompt the user to buy it. If it is, let them continue to the app.

This only works if you need a one time payment. If you need a subscription, you will have to make it up of multiple one time payments, as subscriptions are like managed purchases and can only be paid for once by any account.