Android In-App Billing v3 using ServiceConnection Class

In this tutorial, we are going to learn how to integrate android In-App Purchase using ServiceConnection class.
In-app purchase is a way to sell non-physical or digital goods or services in your app. If you are planning to sell physical goods, I will suggest you go through my tutorial on Android Pay or Android Paypal Integration Tutorial
Most of the tutorials online make use of the android source code example TrivialDrive Project but in this tutorial like the title suggested, we are going to make use of the ServiceConnection class.
The latest version of android in-app billing API is version 3 and this tutorial will focus on this version.

The Android Application Screenshot

 

In-App Billing Version 3 features

In-app Billing Version 3 provides the following features:
Your app sends requests through a streamlined API that allows users to easily request product details from Google Play and order in-app products. The API quickly restores products based on the user’s ownership.
The API synchronously propagates order information to the device on purchase completion.
All purchases are managed (that is, Google Play keeps track of the user’s ownership of in-app products). The user can’t own multiple copies of an in-app product; only one copy can be owned at any point in time.

Purchased products can be consumed. When consumed, the product reverts to the unowned state and can be purchased again from Google Play.
The API provides support for subscriptions.
Please use the comment box to answer questions related to problem you are facing with the code or suggestions on how to improve the tutorial.
This android in-app billing v3 tutorial has different sections to make it easy to understand.

Install or update Google Play Billing Library

We are going to check if we have Google Play Billing Library installed or if it needs to be updated.
In Android Studio, click the SDK Manager menu icon and the click on Launch Standalone SDK Manager.
In the Android SDK window, scroll down to the Extras category and select Google Play Billing Library. Install or update it is need be.

Prepare Store in your Google Play Developer Console

To test your android app for in-app billing, you need to log into your Google Play Developer Console. If you have not registered with Google as an app publisher, then you will first of all do that.
In the developer console, check if if have a Google Wallet attached to your account.

Create a new Google Wallet Merchant Account

To create a new Google Wallet Merchant Account, Go the Settings menu option inside your developer console page.
Then select Account details and scroll down to the bottom of the page.
Click on create merchant account button.
Follow the remaining instruction to finish up
When you are done, you will see a screen like the one shown below.

For the store list, we will complete the following sections.
1. Store Listing
2. Content Rating
3. Pricing and Distribution
4. APK – For the apk section, will add a signed apk when we create our project.

How to add In-App purchase Products

Go to the In-app product menu in the left hand side of the page
There are two type of in-app purchase products – Managed product and Subscription products
We will focus on the Managed Product
Click on Add new product button
Add the title and description for the product
Set a price for the product
When you are done, make sure you click on the inactive button and activate this product.
We have add the following products as shown in the screen shot below.

CREATE ANDROID APPLICATION

Lets start to soil our hands in code. Start up your IDE. For this tutorial, I am using the following tools and environment, feel free to use what works for you.
Windows 10
Android Studio
Sony Xperia ZL
Min SDK 14
Target SDK 23
To create a new android application project, follow the steps as stipulated below.
Go to File menu
Click on New menu
Click on Android Application
Enter Project name: AndroidInAppPurchase
Package: com.inducesmile.androidinapppurchase
Select Blank Activity
Name your activity : MainActivity
Keep other default selections
Continue to click on next button until Finish button is active, then click on Finish Button.

Steps to follow to Integrate In-app Billing library in our project

Update your AndroidManifest.xml file.
Create a ServiceConnection and bind it to IInAppBillingService.
Send In-app Billing requests from your application to IInAppBillingService.
Handle In-app Billing responses from Google Play.

Update AndroidManifest.xml

We are going to update the AndroidManifest.xml file by adding the following user permissions

<uses-permission android:name="com.android.vending.BILLING" />

The android vending billing permission handles all communication between your application and the Google Play server.
Open the Manifest.xml file and add the permissions

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.inducesmile.androidinapppurchase">
    <uses-permission android:name="com.android.vending.BILLING" />
    <uses-permission android:name="android.permission.INTERNET" />
    <application
        android:allowBackup="true"
        android:icon="@mipmap/ic_launcher"
        android:label="@string/app_name"
        android:supportsRtl="true"
        android:theme="@style/AppTheme">
        <activity android:name=".MainActivity">
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />
                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
        <activity android:name=".InAppPurchaseActivity" />
        <activity android:name=".PrivateContentActivity"> </activity>
    </application>
</manifest>

Adding the AIDL file to your project

IInAppBillingService.aidl is an Android Interface Definition Language (AIDL) file that defines the interface to the In-app Billing Version 3 service. You will use this interface to make billing requests by invoking IPC method calls.
To get the AIDL file:
Open the Android SDK Manager.
In the SDK Manager, expand the Extras section.
Select Google Play Billing Library.
Click Install packages to complete the download.
The IInAppBillingService.aidl file will be installed to /extras/google/play_billing/.

To add the AIDL to your project:

First, download the Google Play Billing Library to your Android project:
Select Tools > Android > SDK Manager.
Under Appearance & Behavior > System Settings > Android SDK, select the SDK Tools tab to
select and download Google Play Billing Library.
Next, copy the IInAppBillingService.aidl file to your project.
If you are using Android Studio:
Navigate to src/main in the Project tool window.
Select File > New > Directory and enter aidl in the New Directory window, then select OK.
Select File > New > Package and enter com.android.vending.billing in the New Package window, then select OK.
Using your operating system file explorer, navigate to /extras/google/play_billing/, copy the IInAppBillingService.aidl file, and paste it into the com.android.vending.billing package in your project.
If you are developing in a non-Android Studio environment: Create the following directory /src/com/android/vending/billing and copy the IInAppBillingService.aidl file into this directory. Put the AIDL file into your project and use the Gradle tool to build your project so that the IInAppBillingService.java file gets generated.
Build your application. You should see a generated file named IInAppBillingService.java in the /gen directory of your project.

Update Dependencies in build.gradle file

We are going to add some library dependencies in the app build.gradle file. The updated version of the app build.gradle file is below.

apply plugin: 'com.android.application'
android {
    compileSdkVersion 24
    buildToolsVersion "24.0.0"
    defaultConfig {
        applicationId "com.inducesmile.androidinapppurchase"
        minSdkVersion 14
        targetSdkVersion 24
        versionCode 2
        versionName "1.1"
    }
    buildTypes {
        release {
            minifyEnabled false
            proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
        }
    }
}
dependencies {
    compile fileTree(dir: 'libs', include: ['*.jar'])
    testCompile 'junit:junit:4.12'
    compile 'com.android.support:appcompat-v7:24.1.1'
    compile 'com.intuit.sdp:sdp-android:1.0.3'
    compile 'com.android.support:support-annotations:24.1.1'
    compile 'org.jetbrains:annotations-java5:15.0'
}

STRINGS.XML

We are going to update our project strings.xml file located in the values folder inside the res folder. Open the file and add the code below to it.

<resources>
    <string name="app_name">Android In-App Purchase</string>
    <string name="slogan">Using in-app purchase to make money</string>
    <string name="download_button">CLICK TO DOWNLOAD FILE</string>
    <string name="buy_gold">BUY GOLD FOR YOUR APP</string>
    <string name="in_app_support">In-app purchase is not supported by your device</string>
    <string name="main_content">Thanks for your purchase and welcome to the paid content section</string>
</resources>

COLORS.XML

Open the colors.xml file in the same location as the strings.xml file and add the code below to the file.

<?xml version="1.0" encoding="utf-8"?>
<resources>
    <color name="colorPrimary">#FF9800</color>
    <color name="colorPrimaryDark">#F57C00</color>
    <color name="colorPrimaryLight">#FFE0B2</color>
    <color name="colorAccent">#FF5722</color>
    <color name="colorPrimaryText">#212121</color>
    <color name="colorSecondaryText">#757575</color>
    <color name="colorIcons">#ffffff</color>
    <color name="colorDivider">#BDBDBD</color>
</resources>

MainActivity.java and activity_main.xml

When we created our project, Android Studio created a default MainActivity.java file and a corresponding activity_main.xml layout file located in the layout folder.
We will use the page as an intro splash page for our application.

activity_main.xml

open the activity_main.xml file and add the code below.

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:background="@color/colorPrimaryLight"
    tools:context="com.inducesmile.androidinapppurchase.MainActivity">
    <ImageView
        android:id="@+id/logo"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:contentDescription="@string/app_name"
        android:layout_centerVertical="true"
        android:src="@drawable/logos"
        android:layout_centerHorizontal="true"/>
    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_centerHorizontal="true"
        android:textColor="@color/colorPrimaryDark"
        android:textStyle="italic"
        android:text="@string/slogan"
        android:layout_marginLeft="@dimen/_16sdp"
        android:layout_marginRight="@dimen/_16sdp"
        android:layout_marginTop="@dimen/_4sdp"
        android:layout_below="@+id/logo"/>
</RelativeLayout>

MainActivity class

The MainActivity class will instantiate a handle with a postDelay of three seconds before the next Activity page will load.

import android.content.Intent;
import android.content.pm.ActivityInfo;
import android.os.Handler;
import android.support.v7.app.ActionBar;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.Window;
import android.view.WindowManager;
public class MainActivity extends AppCompatActivity {
    private final int SPLASH_DISPLAY_LENGTH = 5000;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        requestWindowFeature(Window.FEATURE_NO_TITLE);
        getWindow().setFlags(WindowManager.LayoutParams.FLAG_FULLSCREEN, WindowManager.LayoutParams.FLAG_FULLSCREEN);
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        setRequestedOrientation(ActivityInfo.SCREEN_ORIENTATION_PORTRAIT);
        ActionBar actionBar = getSupportActionBar();
        if(null != actionBar){
            actionBar.hide();
        }
        new Handler().postDelayed(new Runnable(){
            @Override
            public void run(){
                Intent startActivityIntent = new Intent(MainActivity.this, InAppPurchaseActivity.class);
                startActivity(startActivityIntent);
                MainActivity.this.finish();
            }
        }, SPLASH_DISPLAY_LENGTH);
    }
}

InAppPurchaseActivity.java and activity_in_app_purchase.xml

This is where will offer our app users the opportunity to to make in-app purchase. In the layout file, we will give the user the opportunity to make purchase in different denominations.

activity_in_app_purchase.xml

open the layout file above and add the code below to it.

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"
    android:background="@color/colorPrimaryLight"
    tools:context="com.inducesmile.androidinapppurchase.InAppPurchaseActivity">
    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_gravity="center_horizontal"
        android:text="@string/buy_gold"
        android:textSize="@dimen/_20sdp"
        android:layout_marginTop="@dimen/_60sdp"
        android:textColor="@color/colorPrimaryText"
        android:textStyle="bold"/>
    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:paddingTop="@dimen/_20sdp"
        android:gravity="center"
        android:orientation="horizontal">
        <LinearLayout
            android:layout_width="0dp"
            android:layout_height="wrap_content"
            android:layout_weight="1"
            android:gravity="center"
            android:orientation="vertical">
            <ImageView
                android:id="@+id/buy_one"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:layout_margin="@dimen/_4sdp"
                android:adjustViewBounds="true"
                android:src="@drawable/buyone"
                android:contentDescription="@string/app_name"/>
        </LinearLayout>
        <LinearLayout
            android:layout_width="0dp"
            android:layout_height="wrap_content"
            android:layout_weight="1"
            android:gravity="center"
            android:orientation="vertical">
            <ImageView
                android:id="@+id/buy_two"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:layout_margin="@dimen/_4sdp"
                android:src="@drawable/buytwo"
                android:adjustViewBounds="true"
                android:contentDescription="@string/app_name"/>
        </LinearLayout>
        <LinearLayout
            android:layout_width="0dp"
            android:layout_height="wrap_content"
            android:layout_weight="1"
            android:gravity="center"
            android:orientation="vertical">
            <ImageView
                android:id="@+id/buy_three"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:layout_margin="@dimen/_4sdp"
                android:src="@drawable/buythree"
                android:adjustViewBounds="true"
                android:contentDescription="@string/app_name"/>
        </LinearLayout>
    </LinearLayout>
</LinearLayout>

InAppPurchaseActivity.java

For the InAppPurchaseActivity class, we will get the imstances of the View controls that represent the buy buttons for all the three products we have added.
Before a user makes a purchase, we will check if billing is supported with the method below

public boolean isBillingSupported(){
    int response = 1;
    try {
        response = mService.isBillingSupported(3, getPackageName(), "inapp");
    } catch (RemoteException e) {
        e.printStackTrace();
    }
    if(response > 0){
        return false;
    }
    return true;
}

For the whole process of managing android in-app billing, we will create the following methods to execute the tasks mentioned.
1. consumePurchaseItem(String purchaseToken) – it is used to consume available purchase items
2. getAllUserPurchase() – get a list of all the purchases a user has made
3. purchaseItem(String sku) – used to purchase an item with the item id passed as parameter
4. itemPurchaseAvailability() – used to check available items to purchase
An instance of the ServiceConnection class is create and its service is bind to the Interface In-App Billing Service as shown below

ServiceConnection mServiceConn = new ServiceConnection() {
    @Override
    public void onServiceDisconnected(ComponentName name) {
        mService = null;
    }
    @Override
    public void onServiceConnected(ComponentName name, IBinder service) {
        mService = IInAppBillingService.Stub.asInterface(service);
        AvailablePurchaseAsyncTask mAsyncTask = new AvailablePurchaseAsyncTask(appPackageName);
        mAsyncTask.execute();
    }
};

Please note that getAllUserPurchase() and itemPurchaseAvailability() methods should be called in non UI Thread to avoid app crashing.
The complete code for the InAppPurchaseActivity class is as shown below.

import android.app.PendingIntent;
import android.content.ComponentName;
import android.content.Context;
import android.content.Intent;
import android.content.IntentSender;
import android.content.ServiceConnection;
import android.os.AsyncTask;
import android.os.Bundle;
import android.os.IBinder;
import android.os.RemoteException;
import android.support.v7.app.AppCompatActivity;
import android.view.View;
import android.widget.ImageView;
import com.android.vending.billing.IInAppBillingService;
import com.inducesmile.androidinapppurchase.entity.AvailablePurchase;
import com.inducesmile.androidinapppurchase.entity.UserPurchaseItems;
import com.inducesmile.androidinapppurchase.helpers.Helper;
import com.inducesmile.androidinapppurchase.session.CustomSharedPreference;
import org.json.JSONException;
import org.json.JSONObject;
import java.math.BigInteger;
import java.security.SecureRandom;
import java.util.ArrayList;
import java.util.List;
import java.util.Random;
public class InAppPurchaseActivity extends AppCompatActivity {
    private static final String TAG = InAppPurchaseActivity.class.getSimpleName();
    private IInAppBillingService mService;
    private CustomSharedPreference customSharedPreference;
    String[] productIds = new String[]{Helper.ITEM_ONE_ID, Helper.ITEM_TWO_ID, Helper.ITEM_THREE_ID};
    private ImageView buyOneButton, buyTwoButton, buyThreeButton;
    private static final char[] symbols = new char[36];
    static {
        for (int idx = 0; idx < 10; ++idx)
            symbols[idx] = (char) ('0' + idx);
        for (int idx = 10; idx < 36; ++idx)
            symbols[idx] = (char) ('a' + idx - 10);
    }
    private String appPackageName;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_in_app_purchase);
        appPackageName = this.getPackageName();
        Intent serviceIntent = new Intent("com.android.vending.billing.InAppBillingService.BIND");
        serviceIntent.setPackage("com.android.vending");
        bindService(serviceIntent, mServiceConn, Context.BIND_AUTO_CREATE);
        customSharedPreference = new CustomSharedPreference(InAppPurchaseActivity.this);
        buyOneButton = (ImageView)findViewById(R.id.buy_one);
        buyOneButton.setVisibility(View.GONE);
        assert buyOneButton != null;
        buyOneButton.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                if(!isBillingSupported()){
                    Helper.displayMessage(InAppPurchaseActivity.this, getString(R.string.in_app_support));
                    return;
                }
                purchaseItem(Helper.ITEM_ONE_ID);
            }
        });
        buyTwoButton = (ImageView)findViewById(R.id.buy_two);
        buyTwoButton.setVisibility(View.GONE);
        assert buyTwoButton != null;
        buyTwoButton.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                if(!isBillingSupported()){
                    Helper.displayMessage(InAppPurchaseActivity.this, getString(R.string.in_app_support));
                    return;
                }
                purchaseItem(Helper.ITEM_TWO_ID);
            }
        });
        buyThreeButton = (ImageView)findViewById(R.id.buy_three);
        buyThreeButton.setVisibility(View.GONE);
        assert buyThreeButton != null;
        buyThreeButton.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                if(!isBillingSupported()){
                    Helper.displayMessage(InAppPurchaseActivity.this, getString(R.string.in_app_support));
                    return;
                }
                purchaseItem(Helper.ITEM_THREE_ID);
            }
        });
    }
    ServiceConnection mServiceConn = new ServiceConnection() {
        @Override
        public void onServiceDisconnected(ComponentName name) {
            mService = null;
        }
        @Override
        public void onServiceConnected(ComponentName name, IBinder service) {
            mService = IInAppBillingService.Stub.asInterface(service);
            AvailablePurchaseAsyncTask mAsyncTask = new AvailablePurchaseAsyncTask(appPackageName);
            mAsyncTask.execute();
        }
    };
    private void purchaseItem(String sku){
        String generatedPayload = getPayLoad();
        customSharedPreference.setDeveloperPayLoad(generatedPayload);
        try {
            Bundle buyIntentBundle = mService.getBuyIntent(3, getPackageName(), sku, "inapp", generatedPayload);
            PendingIntent pendingIntent = buyIntentBundle.getParcelable("BUY_INTENT");
            try {
                startIntentSenderForResult(pendingIntent.getIntentSender(), Helper.RESPONSE_CODE, new Intent(), Integer.valueOf(0), Integer.valueOf(0), Integer.valueOf(0));
            } catch (IntentSender.SendIntentException e) {
                e.printStackTrace();
            }
        } catch (RemoteException e) {
            e.printStackTrace();
        }
    }
    @Override
    protected void onActivityResult(int requestCode, int resultCode, Intent data) {
        if (requestCode == Helper.RESPONSE_CODE) {
            int responseCode = data.getIntExtra("RESPONSE_CODE", 0);
            String purchaseData = data.getStringExtra("INAPP_PURCHASE_DATA");
            String dataSignature = data.getStringExtra("INAPP_DATA_SIGNATURE");
            if (resultCode == RESULT_OK) {
                try {
                    JSONObject purchaseJsonObject = new JSONObject(purchaseData);
                    String sku = purchaseJsonObject.getString("productId");
                    String developerPayload = purchaseJsonObject.getString("developerPayload");
                    String purchaseToken = purchaseJsonObject.getString("purchaseToken");
                    //the developerPayload value is better stored in remote database but in this tutorial
                    //we will use a shared preference
                    for(int i = 0; i < productIds.length; i++){
                        if(productIds[i].equals(sku) && developerPayload.equals(customSharedPreference.getDeveloperPayload())){
                            customSharedPreference.setPurchaseToken(purchaseToken);
                            //access to private content
                            Intent contentIntent = new Intent(InAppPurchaseActivity.this, PrivateContentActivity.class);
                            startActivity(contentIntent);
                        }
                    }
                }
                catch (JSONException e) {
                    e.printStackTrace();
                }
            }
        }
    }
    private String getPayLoad(){
        RandomString randomString = new RandomString(36);
        String payload = randomString.nextString();
        return payload;
    }
    public class RandomString {
        private final Random random = new Random();
        private final char[] buf;
        public RandomString(int length) {
            if (length < 1)
                throw new IllegalArgumentException("length < 1: " + length);
            buf = new char[length];
        }
        public String nextString() {
            for (int idx = 0; idx < buf.length; ++idx)
                buf[idx] = symbols[random.nextInt(symbols.length)];
            return new String(buf);
        }
    }
    public final class SessionIdentifierGenerator {
        private SecureRandom random = new SecureRandom();
        public String nextSessionId() {
            return new BigInteger(130, random).toString(32);
        }
    }
    private class AvailablePurchaseAsyncTask extends AsyncTask<Void, Void, Bundle> {
        String packageName;
        public AvailablePurchaseAsyncTask(String packageName){
            this.packageName = packageName;
        }
        @Override
        protected Bundle doInBackground(Void... voids) {
            ArrayList<String> skuList = new ArrayList<String>();
            skuList.add(Helper.ITEM_ONE_ID);
            skuList.add(Helper.ITEM_TWO_ID);
            skuList.add(Helper.ITEM_THREE_ID);
            Bundle query = new Bundle();
            query.putStringArrayList(Helper.ITEM_ID_LIST, skuList);
            Bundle skuDetails = null;
            try {
                skuDetails = mService.getSkuDetails(3, packageName, "inapp", query);
            } catch (RemoteException e) {
                e.printStackTrace();
            }
            return skuDetails;
        }
        @Override
        protected void onPostExecute(Bundle skuDetails) {
            List<AvailablePurchase> canPurchase = new ArrayList<AvailablePurchase>();
            int response = skuDetails.getInt("RESPONSE_CODE");
            if (response == 0) {
                ArrayList<String> responseList = skuDetails.getStringArrayList("DETAILS_LIST");
                if(responseList != null){
                    for (String thisResponse : responseList) {
                        JSONObject object = null;
                        try {
                            object = new JSONObject(thisResponse);
                            String sku = object.getString("productId");
                            String price = object.getString("price");
                            canPurchase.add(new AvailablePurchase(sku, price));
                        } catch (JSONException e) {
                            e.printStackTrace();
                        }
                    }
                }
            }
            if(checkIfPurchaseIsAvailable(canPurchase, productIds[0])){
                buyOneButton.setVisibility(View.VISIBLE);
            }else{
                buyOneButton.setVisibility(View.GONE);
            }
            if(checkIfPurchaseIsAvailable(canPurchase, productIds[1])){
                buyTwoButton.setVisibility(View.VISIBLE);
            }else{
                buyTwoButton.setVisibility(View.GONE);
            }
            if(checkIfPurchaseIsAvailable(canPurchase, productIds[2])){
                buyThreeButton.setVisibility(View.VISIBLE);
            }else{
                buyThreeButton.setVisibility(View.GONE);
            }
        }
    }
    @org.jetbrains.annotations.Contract("null, _ -> false")
    private boolean checkIfPurchaseIsAvailable(List<AvailablePurchase> all, String productId){
        if(all == null){ return false;}
        for(int i = 0; i < all.size(); i++){
            if(all.get(i).getSku().equals(productId)){
                return true;
            }
        }
        return false;
    }
    public boolean isBillingSupported(){
        int response = 1;
        try {
            response = mService.isBillingSupported(3, getPackageName(), "inapp");
        } catch (RemoteException e) {
            e.printStackTrace();
        }
        if(response > 0){
            return false;
        }
        return true;
    }
    public void consumePurchaseItem(String purchaseToken){
        try {
            int response = mService.consumePurchase(3, getPackageName(), purchaseToken);
            if(response != 0){
                return;
            }
        } catch (RemoteException e) {
            e.printStackTrace();
        }
    }
    public Bundle getAllUserPurchase(){
        Bundle ownedItems = null;
        try {
            ownedItems = mService.getPurchases(3, getPackageName(), "inapp", null);
        } catch (RemoteException e) {
            e.printStackTrace();
        }
        return ownedItems;
    }
    public List<UserPurchaseItems> extractAllUserPurchase(Bundle ownedItems){
        List<UserPurchaseItems> mUserItems = new ArrayList<UserPurchaseItems>();
        int response = ownedItems.getInt("RESPONSE_CODE");
        if (response == 0) {
            ArrayList<String> ownedSkus = ownedItems.getStringArrayList("INAPP_PURCHASE_ITEM_LIST");
            ArrayList<String>  purchaseDataList = ownedItems.getStringArrayList("INAPP_PURCHASE_DATA_LIST");
            ArrayList<String>  signatureList = ownedItems.getStringArrayList("INAPP_DATA_SIGNATURE_LIST");
            String continuationToken = ownedItems.getString("INAPP_CONTINUATION_TOKEN");
            if(purchaseDataList != null){
                for (int i = 0; i < purchaseDataList.size(); ++i) {
                    String purchaseData = purchaseDataList.get(i);
                    assert signatureList != null;
                    String signature = signatureList.get(i);
                    assert ownedSkus != null;
                    String sku = ownedSkus.get(i);
                    UserPurchaseItems allItems = new UserPurchaseItems(sku, purchaseData, signature);
                    mUserItems.add(allItems);
                }
            }
        }
        return mUserItems;
    }
    @Override
    public void onDestroy() {
        super.onDestroy();
        if (mService != null) {
            unbindService(mServiceConn);
        }
    }
}

PrivateContentActivity and activity_private_content.xml

If the purchase is successful, the app will take the user to the Private Content page which is not available for unpaid users.

import android.os.Bundle;
import android.support.v7.app.AppCompatActivity;

public class PrivateContentActivity extends AppCompatActivity{
    private CustomSharedPreference customSharedPreference;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_private_content);
        
        //You can set the condition for consumption of the purchase or it can be one time fee
        //it depends on your application requirement.
        // but if you to consume a purchase, call the method below
        //String token = customSharedPreference.getPurchaseToken();
        // You can call consume purchase
        //consumePurchaseItem(token)
    }
}

Create Entity Package Directory

We will create a new package folder and name it entity. Create the files below and add the contents respectively.

AvailablePurchase.java

public class AvailablePurchase {
    private String sku;
    private String price;
    public AvailablePurchase(String sku, String price) {
        this.sku = sku;
        this.price = price;
    }
    public String getSku() {
        return sku;
    }
    public String getPrice() {
        return price;
    }
}

UserPurchaseItems.java

public class UserPurchaseItems {
    private String sku;
    private String purchasedata;
    private String signature;
    public UserPurchaseItems(String sku, String purchasedata, String signature) {
        this.sku = sku;
        this.purchasedata = purchasedata;
        this.signature = signature;
    }
    public String getSku() {
        return sku;
    }
    public String getPurchasedata() {
        return purchasedata;
    }
    public String getSignature() {
        return signature;
    }
}

Create Helper Package Directory

We will create a new package folder and name it helpers. Inside the package, create a new java file and name it Helper.java.
Add the code below to it.

Helper.java

import android.content.Context;
import android.widget.Toast;
public class Helper {
    public static final String ITEM_ID_LIST = "ITEM_ID_LIST";
    public static final String ITEM_ONE_ID = "productone";
    public static final String ITEM_TWO_ID = "producttwo";
    public static final String ITEM_THREE_ID = "productthree";
    public static final int RESPONSE_CODE = 1001;
    public static final String SHARED_PREF = "shared_pref";
    public static final String DEVELOPER_PAYLOAD = "developer_payload";
    public static final String PURCHASE_TOKEN = "purchase_token";
    public static void displayMessage(Context context, String message){
        Toast.makeText(context.getApplicationContext(), message, Toast.LENGTH_LONG).show();
    }
}

Testing In-App Billing Purchase

To test you are in-app purchase, create a Google+ account and add the users that will test the app in your group or community. Do not use your main Google account to test your In-App purchase.

Errors You might encounter during In-App purchase testing

the item you requested is not available for purchase
Solution – According to AndreiBogdan in Stackoverflow,
Here are some things to check:
1. You’ve created an apk and you’ve published it to the GooglePlay Dashboard in Alpha or Beta.
2. The app in the GooglePlay Dashboard is NOT in Draft mode, but in Published (you’ll need to make all the small circles with the check icon in them on the left side of the screen green before being able to publish).
3. You’ve set another test account than the one that’s “attached” to the GooglePlay Dashboard. You can do that by creating a Google+ group, add your test account to that group and specify the Google+ group in the GooglePlay Dashboard.
4. The apk that you’re using to test the purchase has the same version code, version name, and most importantly it’s signed with the same keystore as the apk that you’ve published in the store.
5. You wait a couple of hours between when you change something in the dashboard in order for the changes to propagate. It takes a couple of hours to do so.
6. Make sure the sku value is a valid sku value (compare it with the one you’ve entered in the GP Dashboard).
7. You try to purchase an already purchased item. Get the purchased items and display them in the log to see if so. If so, then consume that product or refund the money to your test account(you’ll need to wait for the refund to propagate. It takes a couple of hours.)
8. Make sure the Inapps are Active !
9. Make sure you’re signedIn into google (in your browser) with the test account and you open this link (marked with the red) and you approve to become a tester !!!!

This brings us to the end of this tutorial. I hope that you have learn something. Run your app and see for yourself.
You can download the code for this tutorial below. If you are having hard time downloading the tutorial, kindly contact me.
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N.B: All data's are copy pasted from this link for study purpose: https://inducesmile.com/android/android-in-app-billing-v3-purchase-using-serviceconnection-example-tutorial/#