Myket In-App Purchase Guide for B4A (Basic4Android)

Basic4Android

Sample project

For the complete B4A library and runnable sample project, see the official sample repository on GitHub.

The Myket In-App Billing SDK for B4A is the official library for integrating Myket In-App Billing (IAB) into Android applications targeting B4A v14.

This SDK wraps Myket's native billing client (ir.myket.billingclient.IabHelper v2.2), exposing its methods and event callbacks in B4A.

Directory Structure

./B4A/
├── MyketBillingLibrary/      # Compiled B4A library files (copy to Additional Libraries)
│   ├── MyketBilling.jar       # B4A Java wrapper binary with embedded manifest macro
│   ├── MyketBilling.xml       # B4A IDE autocomplete & type descriptor
│   └── MyketBilling-2.2.aar   # Underlying Myket Billing SDK AAR (v2.2)
│
├── MyketBillingSample/       # Complete B4A sample application (TrivialDrive)
│   ├── MyketBillingSample.b4a
│   ├── MyketBillingSample.b4a.meta
│   ├── Starter.bas
│   ├── Files/                 # Game graphics and assets
│   └── Objects/               # Compiled APK & build artifacts
│
└── README.md

Prerequisites

A registered developer account on the Myket Developer Portal.
An application registered in your Myket developer panel with a reserved package name.
Your app's RSA Public Key copied from the Myket developer console.
In-app products (SKUs) defined in your application console on Myket.
B4A v14 and Android build tools installed.
A test Android device with the Myket app installed.

Getting Started

1. Install the Library in B4A

Copy all three files from ./B4A/MyketBillingLibrary/ to your B4A Additional Libraries folder:

MyketBilling.jar
MyketBilling.xml
MyketBilling-2.2.aar

In the B4A IDE, refresh the Libraries Manager tab and check MyketBilling (or myketbilling).

2. Configure the Android Manifest

Add the manifest macro in the B4A Manifest Editor (Project -> Manifest Editor):

CreateResourceFromFile(Macro, MyketBilling.MyketBillingReceiver)

The macro automatically configures:

Required permissions (INTERNET, ir.mservices.market.BILLING)
Android 11+ package visibility queries for Myket and Chrome
Required activities (ProxyBillingActivity, PaymentCallbackActivity, CustomTabLauncherActivity)
Metadata (market_id, market_bind_address, sdk_version)
Broadcast receiver (IABReceiver)

3. Required Project Dependencies

Add the following #AdditionalJar directives to your main module's #Region Project Attributes:

#AdditionalJar: androidx.core:core
#AdditionalJar: androidx.browser:browser
#AdditionalJar: org.jetbrains.kotlin-kotlin-stdlib
#AdditionalJar: org.jetbrains.kotlinx-kotlinx-coroutines-core-jvm
#AdditionalJar: org.jetbrains.kotlinx-kotlinx-coroutines-android
#AdditionalJar: okhttp-4.9.0
#AdditionalJar: okio-2.8.0
#AdditionalJar: gson-2.8.5

(All of these JARs / AARs are included by default in B4A v14 / Android SDK).

Code Examples & API Guide

1. Declaration and Initialization

Sub Globals
    Private mHelper As MyketIabHelper ' or MyketBilling
End Sub

Sub Activity_Create(FirstTime As Boolean)
    ' Initialize with EventName prefix and your Base64 Public Key from Myket Console
    mHelper.Initialize("IabHelper", "YOUR_BASE64_PUBLIC_KEY")
    mHelper.EnableDebugLogging(True)
    mHelper.StartSetup
End Sub

2. Setup and Inventory Query Events

' Raised when connection to billing service finishes
Private Sub IabHelper_SetupFinished (Result As MyketIabResult)
    If Result.Success Then
        Log("Connected to Myket billing service successfully.")
        
        ' Query active purchases and product details
        Dim skuList As List
        skuList.Initialize
        skuList.Add("gas")
        skuList.Add("premium")
        mHelper.QueryInventoryAsync3(True, skuList)
    Else
        Log("Billing setup failed: " & Result.Message)
    End If
End Sub

' Raised when inventory query completes
Private Sub IabHelper_QueryInventoryFinished (Result As MyketIabResult, Inventory As MyketInventory)
    If Result.Success Then
        ' 1. Check and consume unconsumed consumable purchases (crash recovery)
        If Inventory.HasPurchase("gas") Then
            Dim gasPurchase As MyketPurchase = Inventory.GetPurchase("gas")
            mHelper.ConsumeAsync(gasPurchase)
        End If

        ' 2. Verify non-consumable ownership
        If Inventory.HasPurchase("premium") Then
            Log("User owns premium upgrade.")
            ' Unlock premium feature
        End If
    Else
        Log("Failed to query inventory: " & Result.Message)
    End If
End Sub

3. Purchasing and Consuming Products

' Launch purchase flow
Sub BuyGas_Click
    mHelper.LaunchPurchaseFlow("gas", "payload_tracking_123")
End Sub

' Raised when purchase flow finishes
Private Sub IabHelper_PurchaseFinished (Result As MyketIabResult, Purchase As MyketPurchase)
    If Result.Success Then
        Log("Purchase successful: " & Purchase.Sku)
        
        ' If consumable (e.g. gas, coins):
        If Purchase.Sku = "gas" Then
            mHelper.ConsumeAsync(Purchase)
        Else
            ' Non-consumable feature unlock
            UnlockFeature
        End If
    Else
        Log("Purchase failed: " & Result.Message)
    End If
End Sub

' Raised when consumption finishes
Private Sub IabHelper_ConsumeFinished (Purchase As MyketPurchase, Result As MyketIabResult)
    If Result.Success Then
        Log("Product consumed successfully: " & Purchase.Sku)
        ' Credit coins or refill gas
    Else
        Log("Failed to consume product: " & Result.Message)
    End If
End Sub

tip

The developerPayload string must not exceed 800 characters.

danger

Never consume non-consumable products. Consuming an item permanently removes it from the user's active inventory on Myket.

4. Lifecycle Management

Release the service connection in Activity_Pause when the user closes the activity:

Sub Activity_Pause (UserClosed As Boolean)
    If UserClosed And mHelper.IsInitialized Then
        mHelper.Dispose
    End If
End Sub

Methods Reference (`MyketIabHelper`)

Method	Description
`Initialize(EventName, Base64PublicKey)`	Initializes the helper with context and RSA public key
`EnableDebugLogging(Enable)`	Enables/disables Logcat debug logs
`EnableDebugLogging2(Enable, Tag)`	Enables/disables debug logs with custom tag
`StartSetup()`	Starts connection to Myket billing service asynchronously
`StartSetup2(EventName)`	Starts connection with a custom callback event prefix
`LaunchPurchaseFlow(Sku, DeveloperPayload)`	Initiates in-app purchase flow with payload
`LaunchPurchaseFlow2(Sku)`	Initiates in-app purchase flow without payload
`LaunchPurchaseFlowCustom(EventName, Sku, ItemType, Payload)`	Initiates flow with custom event and item type
`QueryInventoryAsync()`	Queries owned items and SKU details asynchronously
`QueryInventoryAsync2(QuerySkuDetails)`	Queries owned items, specifying whether to fetch details
`QueryInventoryAsync3(QuerySkuDetails, SkuList)`	Queries owned items + specific SKUs from a B4A `List`
`QueryInventoryAsync4(QuerySkuDetails, SkuIds)`	Queries owned items + specific SKUs from a `String[]`
`ConsumeAsync(Purchase)`	Consumes a purchased item asynchronously
`ConsumeAsync2(EventName, Purchase)`	Consumes a purchased item with custom callback event
`Dispose()`	Disposes helper and releases service connections
`GetResponseDesc(Code)`	Returns human-readable string for numeric response code

Events Reference

Event Signature	Raised When
`Sub EventName_SetupFinished (Result As MyketIabResult)`	Setup completes successfully or with error
`Sub EventName_QueryInventoryFinished (Result As MyketIabResult, Inventory As MyketInventory)`	Inventory query completes
`Sub EventName_PurchaseFinished (Result As MyketIabResult, Purchase As MyketPurchase)`	Purchase flow finishes or is cancelled
`Sub EventName_ConsumeFinished (Purchase As MyketPurchase, Result As MyketIabResult)`	Item consumption finishes

Sample Application (TrivialDrive)

Subscription support

The subscription flow in the sample does not mean Myket currently supports subscriptions. Myket does not currently support subscription products; do not use the subscription example for a real product.

The sample project in ./B4A/MyketBillingSample/ implements the TrivialDrive scenario matching MainActivity.java from the native Android sample:

Consumable Gas ("gas"): Refills the car's tank by 1/4 after each consumption.
Non-Consumable Premium Upgrade ("premium"): Permanently upgrades the car to the red model.
Lifecycle Management: Safely disposes the billing helper in Activity_Pause when UserClosed = True.

Directory Structure​

Prerequisites​

Getting Started​

1. Install the Library in B4A​

2. Configure the Android Manifest​

3. Required Project Dependencies​

Code Examples & API Guide​

1. Declaration and Initialization​

2. Setup and Inventory Query Events​

3. Purchasing and Consuming Products​

4. Lifecycle Management​

Methods Reference (MyketIabHelper)​

Events Reference​

Sample Application (TrivialDrive)​