Consumable Managed Products are products that can be bought multiple times such as in-game currency, game lives, power-ups, etc.

In this example, we are going to implement 4 different consumable managed products "item1", "item2", "item3", "item4".

Steps in summary:

1. Add the In-app Billing library to your project (AIDL File).
2. Add the required permission in AndroidManifest.xml file.
3. Deploy a signed apk to Google Developers Console.
4. Define your products.
5. Implement the code.
6. Test In-app Billing (optional).

Step 1:

First of all, we will need to add the AIDL file to your project as clearly explained in Google Documentation here.

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.

Step 2:

After adding the AIDL file, add BILLING permission in AndroidManifest.xml:

<!-- Required permission for implementing In-app Billing -->
<uses-permission android:name="com.android.vending.BILLING" />

Step 3:

Generate a signed apk, and upload it to Google Developers Console. This is required so that we can start defining our in-app products there.

Step 4:

Define all your products with different productID, and set a price to each one of them. There are 2 types of products (Managed Products and Subscriptions). As we already said, we are going to implement 4 different consumable managed products "item1", "item2", "item3", "item4".

Step 5:

After doing all the steps above, you are now ready to start implementing the code itself in your own activity.

MainActivity:

public class MainActivity extends Activity {

    IInAppBillingService inAppBillingService;
    ServiceConnection serviceConnection;

    // productID for each item. You should define them in the Google Developers Console.
    final String item1 = "item1";
    final String item2 = "item2";
    final String item3 = "item3";
    final String item4 = "item4";

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

        // Instantiate the views according to your layout file.
        final Button buy1 = (Button) findViewById(R.id.buy1);
        final Button buy2 = (Button) findViewById(R.id.buy2);
        final Button buy3 = (Button) findViewById(R.id.buy3);
        final Button buy4 = (Button) findViewById(R.id.buy4);

        // setOnClickListener() for each button.
        // buyItem() here is the method that we will implement to launch the PurchaseFlow.
        buy1.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                buyItem(item1);
            }
        });

        buy2.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                buyItem(item2);
            }
        });

        buy3.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                buyItem(item3);
            }
        });

        buy4.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                buyItem(item4);
            }
        });

        // Attach the service connection.
        serviceConnection = new ServiceConnection() {
            @Override
            public void onServiceDisconnected(ComponentName name) {
                inAppBillingService = null;
            }

            @Override
            public void onServiceConnected(ComponentName name, IBinder service) {
                inAppBillingService = IInAppBillingService.Stub.asInterface(service);
            }
        };

        // Bind the service.
        Intent serviceIntent = new Intent("com.android.vending.billing.InAppBillingService.BIND");
        serviceIntent.setPackage("com.android.vending");
        bindService(serviceIntent, serviceConnection, BIND_AUTO_CREATE);

        // Get the price of each product, and set the price as text to
        // each button so that the user knows the price of each item.
        if (inAppBillingService != null) {
            // Attention: You need to create a new thread here because
            // getSkuDetails() triggers a network request, which can
            // cause lag to your app if it was called from the main thread.
            Thread thread = new Thread(new Runnable() {
                @Override
                public void run() {
                    ArrayList<String> skuList = new ArrayList<>();
                    skuList.add(item1);
                    skuList.add(item2);
                    skuList.add(item3);
                    skuList.add(item4);
                    Bundle querySkus = new Bundle();
                    querySkus.putStringArrayList("ITEM_ID_LIST", skuList);

                    try {
                        Bundle skuDetails = inAppBillingService.getSkuDetails(3, getPackageName(), "inapp", querySkus);
                        int response = skuDetails.getInt("RESPONSE_CODE");

                        if (response == 0) {
                            ArrayList<String> responseList = skuDetails.getStringArrayList("DETAILS_LIST");

                            for (String thisResponse : responseList) {
                                JSONObject object = new JSONObject(thisResponse);
                                String sku = object.getString("productId");
                                String price = object.getString("price");

                                switch (sku) {
                                    case item1:
                                        buy1.setText(price);
                                        break;
                                    case item2:
                                        buy2.setText(price);
                                        break;
                                    case item3:
                                        buy3.setText(price);
                                        break;
                                    case item4:
                                        buy4.setText(price);
                                        break;
                                }
                            }
                        }
                    } catch (RemoteException | JSONException e) {
                        e.printStackTrace();
                    }
                }
            });
            thread.start();
        }
    }

    // Launch the PurchaseFlow passing the productID of the item the user wants to buy as a parameter.
    private void buyItem(String productID) {
        if (inAppBillingService != null) {
            try {
                Bundle buyIntentBundle = inAppBillingService.getBuyIntent(3, getPackageName(), productID, "inapp", "bGoa+V7g/yqDXvKRqq+JTFn4uQZbPiQJo4pf9RzJ");
                PendingIntent pendingIntent = buyIntentBundle.getParcelable("BUY_INTENT");
                startIntentSenderForResult(pendingIntent.getIntentSender(), 1003, new Intent(), 0, 0, 0);
            } catch (RemoteException | IntentSender.SendIntentException e) {
                e.printStackTrace();
            }
        }
    }

    // Unbind the service in onDestroy(). If you don’t unbind, the open
    // service connection could cause your device’s performance to degrade.
    @Override
    public void onDestroy() {
        super.onDestroy();
        if (inAppBillingService != null) {
            unbindService(serviceConnection);
        }
    }

    // Check here if the in-app purchase was successful or not. If it was successful,
    // then consume the product, and let the app make the required changes.
    @Override
    protected void onActivityResult(int requestCode, int resultCode, Intent data) {
        super.onActivityResult(requestCode, resultCode, data);

        if (requestCode == 1003 && resultCode == RESULT_OK) {

            final String purchaseData = data.getStringExtra("INAPP_PURCHASE_DATA");

            // Attention: You need to create a new thread here because
            // consumePurchase() triggers a network request, which can
            // cause lag to your app if it was called from the main thread.
            Thread thread = new Thread(new Runnable() {
                @Override
                public void run() {
                    try {
                        JSONObject jo = new JSONObject(purchaseData);
                        // Get the productID of the purchased item.
                        String sku = jo.getString("productId");
                        String productName = null;

                        // increaseCoins() here is a method used as an example in a game to
                        // increase the in-game currency if the purchase was successful.
                        // You should implement your own code here, and let the app apply
                        // the required changes after the purchase was successful.
                        switch (sku) {
                            case item1:
                                productName = "Item 1";
                                increaseCoins(2000);
                                break;
                            case item2:
                                productName = "Item 2";
                                increaseCoins(8000);
                                break;
                            case item3:
                                productName = "Item 3";
                                increaseCoins(18000);
                                break;
                            case item4:
                                productName = "Item 4";
                                increaseCoins(30000);
                                break;
                        }

                        // Consume the purchase so that the user is able to purchase the same product again.
                        inAppBillingService.consumePurchase(3, getPackageName(), jo.getString("purchaseToken"));
                        Toast.makeText(MainActivity.this, productName + " is successfully purchased. Excellent choice, master!", Toast.LENGTH_LONG).show();
                    } catch (JSONException | RemoteException e) {
                        Toast.makeText(MainActivity.this, "Failed to parse purchase data.", Toast.LENGTH_LONG).show();
                        e.printStackTrace();
                    }
                }
            });
            thread.start();
        }
    }
}

Step 6:

After implementing the code, you can test it by deploying your apk to beta/alpha channel, and let other users test the code for you. However, real in-app purchases can't be made while in testing mode. You have to publish your app/game first to Play Store so that all the products are fully activated.

More info on testing In-app Billing can be found here.

Step 1: First of all follow these two steps to add in app functionality :

1. Add the library using :

 repositories {
            mavenCentral()
        }
        dependencies {
           compile 'com.anjlab.android.iab.v3:library:1.0.+'
        }

2. Add permission in manifest file.

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

Step 2: Initialise your billing processor:

BillingProcessor bp = new BillingProcessor(this, "YOUR LICENSE KEY FROM GOOGLE PLAY CONSOLE HERE", this);

and implement Billing Handler : BillingProcessor.IBillingHandler which contains 4 methods : a. onBillingInitialized(); b. onProductPurchased(String productId, TransactionDetails details) : This is where you need to handle actions to be performed after successful purchase c. onBillingError(int errorCode, Throwable error) : Handle any error occurred during purchase process d. onPurchaseHistoryRestored() : For restoring in app purchases

Step 3: How to purchase a product.

To purchase a managed product :

bp.purchase(YOUR_ACTIVITY, "YOUR PRODUCT ID FROM GOOGLE PLAY CONSOLE HERE");

And to Purchase a subscription :

bp.subscribe(YOUR_ACTIVITY, "YOUR SUBSCRIPTION ID FROM GOOGLE PLAY CONSOLE HERE");

Step 4 : Consuming a product.

To consume a product simply call consumePurchase method.

bp.consumePurchase("YOUR PRODUCT ID FROM GOOGLE PLAY CONSOLE HERE");

For other methods related to in app visit github