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Introduction

In this article we will learn how to integrate and make in app purchase of Single Consumable one-time products using google play billing library.

Tips

Article	Java	Kotlin
For Single Non-consumable one-time product	link	link
For Multiple Non-consumable one-time product	link	link
For Single Consumable one-time product	link	link
For Multiple Consumable one-time product	link	link
For Single In App Subscriptions	link	link
For Multiple In App Subscriptions	link	link

Our Example

In our example we have a textview which shows count of purchased consumable items and a consume button which allow user to purchase consumable item many times. When the item is purchased then we are consuming that item as well as incrementing consumable item count and saving its value (count) to preference.

Requirements:

1. Android Project/App to which In App Purchase Item to be added
2. Google play console account

Note: In order to create in app product consumable items in Google Console or perform real test of in app purchase consumable item in your app, you first need to Integrate Google Play Library and add billing permission in your project and then upload that apk on Google play console and publish it any track (Internal test track (recommended), Closed track, Open track, Production track). Therefore we will perform these actions first.

Steps

Follow below steps

1 Integrate Google Play Library in your project

2 Create an application and fill Store listing in Google play console

3 Upload and publish your app

4 Create Consumable item “consumable” in Google play console

5 Code in app purchase flow logic.

6 Run and Test the application

Step 1 to 3 already explained in this article so follow these steps from there.

4 Create Consumable item “consumable” in Google play console

After releasing app go to Monetize -> Products -> In-app products.

Click on create and fill necessary info then save and activate the product items.

5 Code in app purchase flow logic.

First make sure you have added Google Play Billing Library dependency and billing permission, which was described in step 1.

Then Add textviews consumable_count and consumable_button button in activity_main.xml Layout.

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"
    tools:context=".MainActivity">

    <TextView
        android:id="@+id/consume_count"
        android:gravity="center"
        android:layout_width="match_parent"
        android:layout_height="0dp"
        android:layout_weight="1"
        android:text=""
        />
    <Button
        android:id="@+id/consume_button"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:gravity="center"
        android:text="Consume"
        android:onClick="consume"
    />

</LinearLayout>

In order to make In-App purchase our MainActivity needs to implements PurchasesUpdatedListener interface and override onPurchasesUpdated() method which will be called every time to get notifications for purchases updates. Both purchases initiated by your app and the ones initiated outside of your app will be reported here.

We also need to create BillingClient Object and set listener to it so that we can communicate with Google Play Billing Service.

public class MainActivity extends AppCompatActivity implements PurchasesUpdatedListener {

    private BillingClient billingClient;
    @Override
    protected void onCreate(Bundle savedInstanceState) {

        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        billingClient = BillingClient.newBuilder(this)
                .enablePendingPurchases().setListener(this).build();
    }

    @Override
    public void onPurchasesUpdated(BillingResult billingResult, @Nullable 
 List<Purchase> purchases) {
        //we will code purchase result logic later
    }
}

On consume button click we will initiate purchase flow

//initiate purchase on consume button click
public void consume(View view) {
	//check if service is already connected
	if (billingClient.isReady()) {
		initiatePurchase();
	}
	//else reconnect service
	else{
		billingClient = BillingClient.newBuilder(this).enablePendingPurchases().setListener(this).build();
		billingClient.startConnection(new BillingClientStateListener() {
			@Override
			public void onBillingSetupFinished(@NonNull BillingResult billingResult) {
				if (billingResult.getResponseCode() == BillingClient.BillingResponseCode.OK) {
					initiatePurchase();
				} else {
					Toast.makeText(getApplicationContext(),"Error "+billingResult.getDebugMessage(),Toast.LENGTH_SHORT).show();
				}
			}
			@Override
			public void onBillingServiceDisconnected() {
			}
		});
	}
}

In initiatePurchase() method we have included product id “consumable”, which was added in Google Play Console inside in app products, specified product type as INAPP. Then we have called querySkuDetailsAsync() method which will query our product from Play console. After querying we will call launchBillingFlow() method which will display purchase dialog. Result of purchase dialog will be reported inside onPurchasesUpdated() method which we will code next.

private void initiatePurchase() {
	List<String> skuList = new ArrayList<>();
	skuList.add(PRODUCT_ID);
	SkuDetailsParams.Builder params = SkuDetailsParams.newBuilder();
	params.setSkusList(skuList).setType(INAPP);
	billingClient.querySkuDetailsAsync(params.build(),
			new SkuDetailsResponseListener() {
				@Override
				public void onSkuDetailsResponse(@NonNull BillingResult billingResult,
												 List<SkuDetails> skuDetailsList) {
					if (billingResult.getResponseCode() == BillingClient.BillingResponseCode.OK) {
						if (skuDetailsList != null && skuDetailsList.size() > 0) {
							BillingFlowParams flowParams = BillingFlowParams.newBuilder()
									.setSkuDetails(skuDetailsList.get(0))
									.build();
							billingClient.launchBillingFlow(MainActivity.this, flowParams);
						}
						else{
							//try to add item/product id "consumable" inside managed product in google play console
							Toast.makeText(getApplicationContext(),"Purchase Item not Found",Toast.LENGTH_SHORT).show();
						}
					} else {
						Toast.makeText(getApplicationContext(),
								" Error "+billingResult.getDebugMessage(), Toast.LENGTH_SHORT).show();
					}
				}
			});
}

In onPurchasesUpdated() method we will check purchase result and handle it accordingly.

@Override
public void onPurchasesUpdated(BillingResult billingResult, @Nullable List<Purchase> purchases) {
	//if item newly purchased
	if (billingResult.getResponseCode() == BillingClient.BillingResponseCode.OK && purchases != null) {
		handlePurchases(purchases);
	}
	//if item already purchased then check and reflect changes
	else if (billingResult.getResponseCode() == BillingClient.BillingResponseCode.ITEM_ALREADY_OWNED) {
		Purchase.PurchasesResult queryAlreadyPurchasesResult = billingClient.queryPurchases(INAPP);
		List<Purchase> alreadyPurchases = queryAlreadyPurchasesResult.getPurchasesList();
		if(alreadyPurchases!=null){
			handlePurchases(alreadyPurchases);
		}
	}
	//if purchase cancelled
	else if (billingResult.getResponseCode() == BillingClient.BillingResponseCode.USER_CANCELED) {
		Toast.makeText(getApplicationContext(),"Purchase Canceled",Toast.LENGTH_SHORT).show();
	}
	// Handle any other error msgs
	else {
		Toast.makeText(getApplicationContext(),"Error "+billingResult.getDebugMessage(),Toast.LENGTH_SHORT).show();
	}
}

In handlePurchases() method we will handle, verify and consume purchase. After the purchase, consume is necessary because failure to properly acknowledge or consume purchase will result in purchase being refunded. For non consumable item we have to acknowledge purchase and for consumable item we have to only consume purchase. After the consuming we will save purchase value in preference and increment consume counter.

This method also toast user to complete transaction if purchase status is pending. In case of unspecified purchase state we toast user “Purchase Status Unknown”

void handlePurchases(List<Purchase>  purchases) {

	for(Purchase purchase:purchases) {
		//if item is purchased
		if (PRODUCT_ID.equals(purchase.getSku()) && purchase.getPurchaseState() == Purchase.PurchaseState.PURCHASED)
		{
			if (!verifyValidSignature(purchase.getOriginalJson(), purchase.getSignature())) {
				// Invalid purchase
				// show error to user
				Toast.makeText(getApplicationContext(), "Error : Invalid Purchase", Toast.LENGTH_SHORT).show();
				return;
			}
			// else purchase is valid
			//if item is purchased and not consumed
			if (!purchase.isAcknowledged()) {
				ConsumeParams consumeParams = ConsumeParams.newBuilder()
						.setPurchaseToken(purchase.getPurchaseToken())
						.build();

				billingClient.consumeAsync(consumeParams, consumeListener);
			}
		}
		//if purchase is pending
		else if( PRODUCT_ID.equals(purchase.getSku()) && purchase.getPurchaseState() == Purchase.PurchaseState.PENDING)
		{
			Toast.makeText(getApplicationContext(),
					"Purchase is Pending. Please complete Transaction", Toast.LENGTH_SHORT).show();
		}
		//if purchase is refunded or unknown
		else if(PRODUCT_ID.equals(purchase.getSku()) && purchase.getPurchaseState() == Purchase.PurchaseState.UNSPECIFIED_STATE)
		{
			Toast.makeText(getApplicationContext(), "Purchase Status Unknown", Toast.LENGTH_SHORT).show();
		}
	}
}

ConsumeResponseListener consumeListener = new ConsumeResponseListener() {
	@Override
	public void onConsumeResponse(BillingResult billingResult, String purchaseToken) {
		if (billingResult.getResponseCode() == BillingClient.BillingResponseCode.OK) {
			int consumeCountValue=getPurchaseCountValueFromPref()+1;
			savePurchaseCountValueToPref(consumeCountValue);
			Toast.makeText(getApplicationContext(), "Item Consumed", Toast.LENGTH_SHORT).show();
			consumeCount.setText("Item Consumed "+getPurchaseCountValueFromPref()+" Time(s)");
		}
	}
};

For verification we have used client side signature verification, which will be performed with in app (less secure). However if you can afford server then you should do verification of purchase through your server (more secure).

In client side verification you need to add your developer’s public key of app.

For old Play Console Design To get key go to Developer Console > Select your app > Development Tools > Services & APIs.

For new Play Console Design To get key go to Developer Console > Select your app > Monetize > Monetization setup

Then paste that key to String variable base64key in below method.

/**
 * Verifies that the purchase was signed correctly for this developer's public key.
 * <p>Note: It's strongly recommended to perform such check on your backend since hackers can
 * replace this method with "constant true" if they decompile/rebuild your app.
 * </p>
 */
private boolean verifyValidSignature(String signedData, String signature) {
	try {
		// To get key go to Developer Console > Select your app > Development Tools > Services & APIs.
		String base64Key = "Add Your Key Here"
		return Security.verifyPurchase(base64Key, signedData, signature);
	} catch (IOException e) {
		return false;
	}
}

Code of Security.java is at whole code section

Up to that point our purchase logic is complete. Now On every app start we will check purchase status of item from Google Play Store Cache using getPurchasesList() method and reflect necessary changes accordingly.

// Establish connection to billing client
//check purchase status from google play store cache on every app start
billingClient = BillingClient.newBuilder(this)
		.enablePendingPurchases().setListener(this).build();
billingClient.startConnection(new BillingClientStateListener() {
	@Override
	public void onBillingSetupFinished(@NonNull BillingResult billingResult) {
		if(billingResult.getResponseCode()==BillingClient.BillingResponseCode.OK){
			Purchase.PurchasesResult queryPurchase = billingClient.queryPurchases(INAPP);
			List<Purchase> queryPurchases = queryPurchase.getPurchasesList();
			if(queryPurchases!=null && queryPurchases.size()>0){
				handlePurchases(queryPurchases);
			}
		}
	}

	@Override
	public void onBillingServiceDisconnected() {
	}
});

consumeCount.setText("Item Consumed "+getPurchaseCountValueFromPref()+" Time(s)");

Whole Code

App level build.gradle

apply plugin: 'com.android.application'

android {
    compileSdkVersion 30
    buildToolsVersion "29.0.3"
    defaultConfig {
        applicationId "com.programtown.example"
        minSdkVersion 17
        targetSdkVersion 30
        versionCode 1
        versionName "1.0"
        testInstrumentationRunner "androidx.test.runner.AndroidJUnitRunner"
    }
    buildTypes {
        release {
            minifyEnabled false
            proguardFiles getDefaultProguardFile('proguard-android-optimize.txt'), 'proguard-rules.pro'
        }
    }
}

dependencies {
    implementation fileTree(dir: 'libs', include: ['*.jar'])
    implementation 'androidx.appcompat:appcompat:1.2.0'
    implementation 'androidx.constraintlayout:constraintlayout:2.0.2'
    testImplementation 'junit:junit:4.12'
    androidTestImplementation 'androidx.test.ext:junit:1.1.2'
    androidTestImplementation 'androidx.test.espresso:espresso-core:3.3.0'

    implementation 'com.android.billingclient:billing:3.0.1'
}

Manifest File

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.programtown.example">

    <uses-permission android:name="com.android.vending.BILLING" />
    <application
        android:allowBackup="true"
        android:icon="@mipmap/ic_launcher"
        android:label="@string/app_name"
        android:roundIcon="@mipmap/ic_launcher_round"
        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>
    </application>

</manifest>

activity_main.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"
    tools:context=".MainActivity">

    <TextView
        android:id="@+id/consume_count"
        android:gravity="center"
        android:layout_width="match_parent"
        android:layout_height="0dp"
        android:layout_weight="1"
        android:text=""
        />
    <Button
        android:id="@+id/consume_button"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:gravity="center"
        android:text="Consume"
        android:onClick="consume"
    />

</LinearLayout>

MainActivity.java

package com.programtown.example;

import androidx.annotation.NonNull;
import androidx.appcompat.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.TextView;
import android.widget.Toast;
import android.content.SharedPreferences;
import androidx.annotation.Nullable;
import com.android.billingclient.api.AcknowledgePurchaseParams;
import com.android.billingclient.api.AcknowledgePurchaseResponseListener;
import com.android.billingclient.api.BillingClient;
import com.android.billingclient.api.BillingClientStateListener;
import com.android.billingclient.api.BillingFlowParams;
import com.android.billingclient.api.BillingResult;
import com.android.billingclient.api.ConsumeParams;
import com.android.billingclient.api.ConsumeResponseListener;
import com.android.billingclient.api.Purchase;
import com.android.billingclient.api.PurchasesUpdatedListener;
import com.android.billingclient.api.SkuDetails;
import com.android.billingclient.api.SkuDetailsParams;
import com.android.billingclient.api.SkuDetailsResponseListener;



import static com.android.billingclient.api.BillingClient.SkuType.INAPP;

import java.io.IOException;
import java.util.ArrayList;
import java.util.List;

public class MainActivity extends AppCompatActivity implements PurchasesUpdatedListener {

    public static final String PREF_FILE= "MyPref";
    public static final String PURCHASE_KEY= "consumable";
    public static final String PRODUCT_ID= "consumable";

    Button consumeButton;
    TextView  consumeCount;

    private BillingClient billingClient;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        consumeButton=(Button) findViewById(R.id.consume_button);
        consumeCount=(TextView) findViewById(R.id.consume_count);

        // Establish connection to billing client
        //check purchase status from google play store cache on every app start
        billingClient = BillingClient.newBuilder(this)
                .enablePendingPurchases().setListener(this).build();
        billingClient.startConnection(new BillingClientStateListener() {
            @Override
            public void onBillingSetupFinished(@NonNull BillingResult billingResult) {
                if(billingResult.getResponseCode()==BillingClient.BillingResponseCode.OK){
                    Purchase.PurchasesResult queryPurchase = billingClient.queryPurchases(INAPP);
                    List<Purchase> queryPurchases = queryPurchase.getPurchasesList();
                    if(queryPurchases!=null && queryPurchases.size()>0){
                        handlePurchases(queryPurchases);
                    }
                }
            }

            @Override
            public void onBillingServiceDisconnected() {
            }
        });

        consumeCount.setText("Item Consumed "+getPurchaseCountValueFromPref()+" Time(s)");
    }

    private SharedPreferences getPreferenceObject() {
        return getApplicationContext().getSharedPreferences(PREF_FILE, 0);
    }
    private SharedPreferences.Editor getPreferenceEditObject() {
        SharedPreferences pref = getApplicationContext().getSharedPreferences(PREF_FILE, 0);
        return pref.edit();
    }
    private int getPurchaseCountValueFromPref(){
        return getPreferenceObject().getInt( PURCHASE_KEY,0);
    }
    private void savePurchaseCountValueToPref(int value){
        getPreferenceEditObject().putInt(PURCHASE_KEY,value).commit();
    }

    //initiate purchase on consume button click
    public void consume(View view) {
        //check if service is already connected
        if (billingClient.isReady()) {
            initiatePurchase();
        }
        //else reconnect service
        else{
            billingClient = BillingClient.newBuilder(this).enablePendingPurchases().setListener(this).build();
            billingClient.startConnection(new BillingClientStateListener() {
                @Override
                public void onBillingSetupFinished(@NonNull BillingResult billingResult) {
                    if (billingResult.getResponseCode() == BillingClient.BillingResponseCode.OK) {
                        initiatePurchase();
                    } else {
                        Toast.makeText(getApplicationContext(),"Error "+billingResult.getDebugMessage(),Toast.LENGTH_SHORT).show();
                    }
                }
                @Override
                public void onBillingServiceDisconnected() {
                }
            });
        }
    }
    private void initiatePurchase() {
        List<String> skuList = new ArrayList<>();
        skuList.add(PRODUCT_ID);
        SkuDetailsParams.Builder params = SkuDetailsParams.newBuilder();
        params.setSkusList(skuList).setType(INAPP);
        billingClient.querySkuDetailsAsync(params.build(),
                new SkuDetailsResponseListener() {
                    @Override
                    public void onSkuDetailsResponse(@NonNull BillingResult billingResult,
                                                     List<SkuDetails> skuDetailsList) {
                        if (billingResult.getResponseCode() == BillingClient.BillingResponseCode.OK) {
                            if (skuDetailsList != null && skuDetailsList.size() > 0) {
                                BillingFlowParams flowParams = BillingFlowParams.newBuilder()
                                        .setSkuDetails(skuDetailsList.get(0))
                                        .build();
                                billingClient.launchBillingFlow(MainActivity.this, flowParams);
                            }
                            else{
                                //try to add item/product id "consumable" inside managed product in google play console
                                Toast.makeText(getApplicationContext(),"Purchase Item not Found",Toast.LENGTH_SHORT).show();
                            }
                        } else {
                            Toast.makeText(getApplicationContext(),
                                    " Error "+billingResult.getDebugMessage(), Toast.LENGTH_SHORT).show();
                        }
                    }
                });
    }

    @Override
    public void onPurchasesUpdated(BillingResult billingResult, @Nullable List<Purchase> purchases) {
        //if item newly purchased
        if (billingResult.getResponseCode() == BillingClient.BillingResponseCode.OK && purchases != null) {
            handlePurchases(purchases);
        }
        //if item already purchased then check and reflect changes
        else if (billingResult.getResponseCode() == BillingClient.BillingResponseCode.ITEM_ALREADY_OWNED) {
            Purchase.PurchasesResult queryAlreadyPurchasesResult = billingClient.queryPurchases(INAPP);
            List<Purchase> alreadyPurchases = queryAlreadyPurchasesResult.getPurchasesList();
            if(alreadyPurchases!=null){
                handlePurchases(alreadyPurchases);
            }
        }
        //if purchase cancelled
        else if (billingResult.getResponseCode() == BillingClient.BillingResponseCode.USER_CANCELED) {
            Toast.makeText(getApplicationContext(),"Purchase Canceled",Toast.LENGTH_SHORT).show();
        }
        // Handle any other error msgs
        else {
            Toast.makeText(getApplicationContext(),"Error "+billingResult.getDebugMessage(),Toast.LENGTH_SHORT).show();
        }
    }
    void handlePurchases(List<Purchase>  purchases) {

        for(Purchase purchase:purchases) {
            //if item is purchased
            if (PRODUCT_ID.equals(purchase.getSku()) && purchase.getPurchaseState() == Purchase.PurchaseState.PURCHASED)
            {
                if (!verifyValidSignature(purchase.getOriginalJson(), purchase.getSignature())) {
                    // Invalid purchase
                    // show error to user
                    Toast.makeText(getApplicationContext(), "Error : Invalid Purchase", Toast.LENGTH_SHORT).show();
                    return;
                }
                // else purchase is valid
                //if item is purchased and not consumed
                if (!purchase.isAcknowledged()) {
                    ConsumeParams consumeParams = ConsumeParams.newBuilder()
                            .setPurchaseToken(purchase.getPurchaseToken())
                            .build();

                    billingClient.consumeAsync(consumeParams, consumeListener);
                }
            }
            //if purchase is pending
            else if( PRODUCT_ID.equals(purchase.getSku()) && purchase.getPurchaseState() == Purchase.PurchaseState.PENDING)
            {
                Toast.makeText(getApplicationContext(),
                        "Purchase is Pending. Please complete Transaction", Toast.LENGTH_SHORT).show();
            }
            //if purchase is refunded or unknown
            else if(PRODUCT_ID.equals(purchase.getSku()) && purchase.getPurchaseState() == Purchase.PurchaseState.UNSPECIFIED_STATE)
            {
                Toast.makeText(getApplicationContext(), "Purchase Status Unknown", Toast.LENGTH_SHORT).show();
            }
        }
    }

    ConsumeResponseListener consumeListener = new ConsumeResponseListener() {
        @Override
        public void onConsumeResponse(BillingResult billingResult, String purchaseToken) {
            if (billingResult.getResponseCode() == BillingClient.BillingResponseCode.OK) {
                int consumeCountValue=getPurchaseCountValueFromPref()+1;
                savePurchaseCountValueToPref(consumeCountValue);
                Toast.makeText(getApplicationContext(), "Item Consumed", Toast.LENGTH_SHORT).show();
                consumeCount.setText("Item Consumed "+getPurchaseCountValueFromPref()+" Time(s)");
            }
        }
    };

    /**
     * Verifies that the purchase was signed correctly for this developer's public key.
     * <p>Note: It's strongly recommended to perform such check on your backend since hackers can
     * replace this method with "constant true" if they decompile/rebuild your app.
     * </p>
     */
    private boolean verifyValidSignature(String signedData, String signature) {
        try {
            //for old playconsole
            // To get key go to Developer Console > Select your app > Development Tools > Services & APIs.
            //for new play console
            //To get key go to Developer Console > Select your app > Monetize > Monetization setup

            String base64Key = "Add your key here";
            return Security.verifyPurchase(base64Key, signedData, signature);
        } catch (IOException e) {
            return false;
        }
    }

    @Override
    protected void onDestroy() {
        super.onDestroy();
        if(billingClient!=null){
            billingClient.endConnection();
        }
    }
}

Security.java

/*
 * Copyright (c) 2012 Google Inc.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.programtown.example;

import android.text.TextUtils;
import android.util.Base64;
import java.io.IOException;
import java.security.InvalidKeyException;
import java.security.KeyFactory;
import java.security.NoSuchAlgorithmException;
import java.security.PublicKey;
import java.security.Signature;
import java.security.SignatureException;
import java.security.spec.InvalidKeySpecException;
import java.security.spec.X509EncodedKeySpec;

/**
 * Security-related methods. For a secure implementation, all of this code should be implemented on
 * a server that communicates with the application on the device.
 */
public class Security {
    private static final String TAG = "IABUtil/Security";

    private static final String KEY_FACTORY_ALGORITHM = "RSA";
    private static final String SIGNATURE_ALGORITHM = "SHA1withRSA";

    /**
     * Verifies that the data was signed with the given signature, and returns the verified
     * purchase.
     * @param base64PublicKey the base64-encoded public key to use for verifying.
     * @param signedData the signed JSON string (signed, not encrypted)
     * @param signature the signature for the data, signed with the private key
     * @throws IOException if encoding algorithm is not supported or key specification
     * is invalid
     */
    public static boolean verifyPurchase(String base64PublicKey, String signedData,
                                         String signature) throws IOException {
        if (TextUtils.isEmpty(signedData) || TextUtils.isEmpty(base64PublicKey)
                || TextUtils.isEmpty(signature)) {
             //Purchase verification failed: missing data
            return false;
        }

        PublicKey key = generatePublicKey(base64PublicKey);
        return verify(key, signedData, signature);
    }

    /**
     * Generates a PublicKey instance from a string containing the Base64-encoded public key.
     *
     * @param encodedPublicKey Base64-encoded public key
     * @throws IOException if encoding algorithm is not supported or key specification
     * is invalid
     */
    public static PublicKey generatePublicKey(String encodedPublicKey) throws IOException {
        try {
            byte[] decodedKey = Base64.decode(encodedPublicKey, Base64.DEFAULT);
            KeyFactory keyFactory = KeyFactory.getInstance(KEY_FACTORY_ALGORITHM);
            return keyFactory.generatePublic(new X509EncodedKeySpec(decodedKey));
        } catch (NoSuchAlgorithmException e) {
            // "RSA" is guaranteed to be available.
            throw new RuntimeException(e);
        } catch (InvalidKeySpecException e) {
            String msg = "Invalid key specification: " + e;
            throw new IOException(msg);
        }
    }

    /**
     * Verifies that the signature from the server matches the computed signature on the data.
     * Returns true if the data is correctly signed.
     *
     * @param publicKey public key associated with the developer account
     * @param signedData signed data from server
     * @param signature server signature
     * @return true if the data and signature match
     */
    public static boolean verify(PublicKey publicKey, String signedData, String signature) {
        byte[] signatureBytes;
        try {
            signatureBytes = Base64.decode(signature, Base64.DEFAULT);
        } catch (IllegalArgumentException e) {
           //Base64 decoding failed
            return false;
        }
        try {
            Signature signatureAlgorithm = Signature.getInstance(SIGNATURE_ALGORITHM);
            signatureAlgorithm.initVerify(publicKey);
            signatureAlgorithm.update(signedData.getBytes());
            if (!signatureAlgorithm.verify(signatureBytes)) {
               //Signature verification failed
                return false;
            }
            return true;
        } catch (NoSuchAlgorithmException e) {
            // "RSA" is guaranteed to be available
            throw new RuntimeException(e);
        } catch (InvalidKeyException e) {
           //Invalid key specification
        } catch (SignatureException e) {
            //Signature exception
        }
        return false;
    }
}

6 Run and Test the application

Now Run your app and test in app purchase by using your gmail account that is associated with your Google Console developer account. Because by default, the only test account registered is the one that’s associated with your developer account. You can register additional test accounts by using the Google Play Console.

Conclusion

So in this article we have learnt how to integrate and make in app purchase of single consumable product. If you liked the article then please share this page and article. Thanks.

NOTE:

If you need personal technical assistance for integrating Google Play Billing Library with latest version than you can book order with me via Fiver here.

References:

https://developer.android.com/google/play/billing/billing_overview

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