In-App PlayStore purchases using Qt Purchasing

Implementing In-App purchases for PlayStore using Qt Purchasing is pretty simple and straightforward.

We will assume that the application is ready to be deployed on an android device (if that's not the case, see here)

Getting started

First off we want to add the Qt Purchasing library to the .pro file of the project, by adding this line to the file

QT += purchasing

Then we want to include the library in the classes that will use it

#include <QtPurchasing>

We want to create a global instance of QInAppStore, which we will use to purchase or register items

QInAppStore inAppStore = new QInAppStore(this);

Connections

We need to setup the connections needed to make in-app purchases work, so we will mark down slots for when a correct product is registered, when an unknown product is registered and when transactions are handled

connect(myStore, SIGNAL(productRegistered(QInAppProduct*)),
        this, SLOT(handleCorrectProduct(QInAppProduct*)));
        
connect(myStore, SIGNAL(productUnknown(QInAppProduct*)),
        this, SLOT(handleUnknownProduct(QInAppProduct*)));

connect(myStore, SIGNAL(transactionReady(QInAppTransaction*)),
        this, SLOT(handleTransactions(QInAppTransaction*)));

Registering Products

After the connections are in place, we need to finally register the in-app products

There are two types of in-app purchases

• Consumables: objects that can be purchased multiple times
• Unlockables: objects that can be purchased only once

Knowing this we will register the products accordingly

myStore->registerProduct(QInAppProduct::Consumable, QStringLiteral("consumable_product"));

or

myStore->registerProduct(QInAppProduct::Unlockable, QStringLiteral("unlockable_product"));

or both if we need to have different in-app purchases.

Purchase a product

When we want to start the purchase of an in-app product we might want to implement a similar code

QInAppProduct *product = myStore->registeredProduct(QStringLiteral("consumable_product"));

or

QInAppProduct *product = myStore->registeredProduct(QStringLiteral("unlockable_product"));

Then check that the product is in fact registered

// Should not get here if product is not registered
Q_ASSERT(product != 0);

And proceed with the purchase

product->purchase();

Once the purchase is concluded (approved or failed) a transactionReady(QInAppTransaction***)**

Handling Transactions

Transactions occur when the signal transactionReady(QInAppTransaction***)** is emitted. In this slot we will need to handle a correct purchase or a failed purchase. It's importante to finalize transactions.

void handleTransactions(QInAppTransaction* transaction)
{

    if (transaction->status() == QInAppTransaction::PurchaseApproved)
    {
        if (transaction->product()->identifier() == QStringLiteral("consumable_product"))
        {
            purchaseConsumableProduct();
        }
        else if (transaction->product()->identifier() == QStringLiteral("unlockable_product"))
        {
            purchaseUnlockableProduct();
        }
        transaction->finalize();
    }
    else if (transaction->status() == QInAppTransaction::PurchaseFailed)
    {
        QMessageBox msgBox;
        msgBox.setText("The purchase has not been completed or an error occurred");
        msgBox.exec();
        transaction->finalize();
    }
}

##Restoring purchases

We want to provide a way to restore previously purchased unlockable products So we will have to invoke

myStore->restorePurchases();

when we want to proceed to that action. Then we will have to add this block of code in the handleTransactions function

if (transaction->status() == QInAppTransaction::PurchaseRestored
	&& transaction->product()->identifier() == QStringLiteral("unlockable_product"))
{
    restoreUnlockableProduct();
    transaction->finalize();
}

Allowing the user to restore previously purchased unlockable content.

Register Products on the Play Store

This part will be about register in-app products on the Play Store If the app is ready to be deployed, then you just need to follow this steps. Otherwhise, you shold check this.

Head over to the Google Play Console, and log in. Access to the application you want to monetize and go to Store Presence - In-app products

Qt Purchasing can only work with managed products, so we will work with that. Click on Create Managed Product

On Product ID give the same name you used to identify the product on your code (in our example, it would be either consumable_product or unlockable_product)

Then proceed to fill out informations about the product (Title, description and price) In the end activate its status by clicking on Active

QtPurchasing and the Windows Store

Currently QtPurchasing doesn't support Windows Store InApp purchases