purchaseProduct
Purchases storeProduct. If storeProduct represents a subscription, upgrades from the subscription specified by upgradeInfo.oldProductId and chooses storeProduct's default SubscriptionOption.
If storeProduct represents a non-subscription, upgradeInfo will be ignored.
Parameters
Current activity
The StoreProduct of the product you wish to purchase
The upgradeInfo you wish to upgrade from, containing the oldProductId and the optional prorationMode. Amazon Appstore doesn't support changing products so upgradeInfo is ignored for Amazon purchases.
The PurchaseCallback that will be called when purchase completes.
Purchases a StoreProduct. If purchasing a subscription, it will choose the default SubscriptionOption.
Parameters
Current activity
The StoreProduct of the product you wish to purchase
The PurchaseCallback that will be called when purchase completes.