Android Application : In-app Billing Example. Test app at https://play.google.com/store/apps/details?id=com.ethanf.in_app_billing_ex

activity_main.xml

<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:paddingBottom="@dimen/activity_vertical_margin"
    android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin"
    tools:context=".MainActivity" >

    <Button
        android:id="@+id/btnTest"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_alignParentLeft="true"
        android:layout_alignParentTop="true"
        android:text="Test" />

    <Button
        android:id="@+id/btnCheck"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_alignLeft="@+id/btnTest"
        android:layout_below="@+id/btnTest"
        android:text="Check" />

    <Button
        android:id="@+id/btnBuy"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_alignLeft="@+id/btnCheck"
        android:layout_below="@+id/btnCheck"
        android:text="Buy" />

    <Button
        android:id="@+id/btnConsume"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_alignParentLeft="true"
        android:layout_below="@+id/btnBuy"
        android:text="Consume" />

</RelativeLayout>

MainActivity.java

package com.ethanf.in_app_billing_ex;

import java.util.ArrayList;

import org.json.JSONException;
import org.json.JSONObject;

import com.android.vending.billing.IInAppBillingService;

import android.os.Bundle;
import android.os.IBinder;
import android.os.RemoteException;
import android.util.Log;
import android.view.View;
import android.widget.Button;
import android.widget.Toast;
import android.app.Activity;
import android.app.PendingIntent;
import android.content.ComponentName;
import android.content.Context;
import android.content.Intent;
import android.content.IntentSender.SendIntentException;
import android.content.ServiceConnection;

public class MainActivity extends Activity {
	private Context context;
	private String tag;

	private IInAppBillingService mService;
	private 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);
		}
	};

	// ProductID
	private final String productID = "android.test.purchased";	// Test Product ID by Google

	// View
	private Button btnTest, btnCheck, btnBuy, btnConsume;

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

		// Context
		context = getApplicationContext();

		// log tag
		tag = "in_app_billing_ex";

		// Bind Service
		final boolean blnBind = bindService(new Intent(
				"com.android.vending.billing.InAppBillingService.BIND"),
				mServiceConn, Context.BIND_AUTO_CREATE);

		Toast.makeText(context, "bindService - return " + String.valueOf(blnBind), Toast.LENGTH_SHORT).show();
		Log.i(tag, "bindService - return " + String.valueOf(blnBind));

		// Assign View
		btnTest    = (Button) findViewById(R.id.btnTest);
		btnCheck   = (Button) findViewById(R.id.btnCheck);
		btnBuy     = (Button) findViewById(R.id.btnBuy);
		btnConsume = (Button) findViewById(R.id.btnConsume);

		btnTest.setOnClickListener(new View.OnClickListener() {
			@Override
			public void onClick(View arg0) {
				if (!blnBind) return;
				if (mService == null) return;

				int result;
				try {
					result = mService.isBillingSupported(3, getPackageName(), "inapp");

					Toast.makeText(context, "isBillingSupported() - success : return " + String.valueOf(result), Toast.LENGTH_SHORT).show();
					Log.i(tag, "isBillingSupported() - success : return " + String.valueOf(result));
				} catch (RemoteException e) {
					e.printStackTrace();

					Toast.makeText(context, "isBillingSupported() - fail!", Toast.LENGTH_SHORT).show();
					Log.w(tag, "isBillingSupported() - fail!");
					return;
				}

				// TODO: check result
			}
		});

		btnCheck.setOnClickListener(new View.OnClickListener() {
			@Override
			public void onClick(View arg0) {
				if (!blnBind) return;
				if (mService == null) return;

				Bundle ownedItems;
				try {
					ownedItems = mService.getPurchases(3, getPackageName(), "inapp", null);

					Toast.makeText(context, "getPurchases() - success return Bundle", Toast.LENGTH_SHORT).show();
					Log.i(tag, "getPurchases() - success return Bundle");
				} catch (RemoteException e) {
					e.printStackTrace();

					Toast.makeText(context, "getPurchases - fail!", Toast.LENGTH_SHORT).show();
					Log.w(tag, "getPurchases() - fail!");
					return;
				}

				int response = ownedItems.getInt("RESPONSE_CODE");
				Toast.makeText(context, "getPurchases() - \"RESPONSE_CODE\" return " + String.valueOf(response), Toast.LENGTH_SHORT).show();
				Log.i(tag, "getPurchases() - \"RESPONSE_CODE\" return " + String.valueOf(response));

				if (response != 0) return;

				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");
				String continuationToken = ownedItems.getString("INAPP_CONTINUATION_TOKEN");

				Log.i(tag, "getPurchases() - \"INAPP_PURCHASE_ITEM_LIST\" return " + ownedSkus.toString());
				Log.i(tag, "getPurchases() - \"INAPP_PURCHASE_DATA_LIST\" return " + purchaseDataList.toString());
				Log.i(tag, "getPurchases() - \"INAPP_DATA_SIGNATURE\" return " + (signatureList != null ? signatureList.toString() : "null"));
				Log.i(tag, "getPurchases() - \"INAPP_CONTINUATION_TOKEN\" return " + (continuationToken != null ? continuationToken : "null"));

				// TODO: management owned purchase
			}
		});

		btnBuy.setOnClickListener(new View.OnClickListener() {
			@Override
			public void onClick(View arg0) {
				if (!blnBind) return;
				if (mService == null) return;

				ArrayList<String> skuList = new ArrayList<String>();
				skuList.add(productID);
				Bundle querySkus = new Bundle();
				querySkus.putStringArrayList("ITEM_ID_LIST", skuList);

				Bundle skuDetails;
				try {
					skuDetails = mService.getSkuDetails(3, getPackageName(), "inapp", querySkus);

					Toast.makeText(context, "getSkuDetails() - success return Bundle", Toast.LENGTH_SHORT).show();
					Log.i(tag, "getSkuDetails() - success return Bundle");
				} catch (RemoteException e) {
					e.printStackTrace();

					Toast.makeText(context, "getSkuDetails() - fail!", Toast.LENGTH_SHORT).show();
					Log.w(tag, "getSkuDetails() - fail!");
					return;
				}

				int response = skuDetails.getInt("RESPONSE_CODE");
				Toast.makeText(context, "getSkuDetails() - \"RESPONSE_CODE\" return " + String.valueOf(response), Toast.LENGTH_SHORT).show();
				Log.i(tag, "getSkuDetails() - \"RESPONSE_CODE\" return " + String.valueOf(response));

				if (response != 0) return;

				ArrayList<String> responseList = skuDetails.getStringArrayList("DETAILS_LIST");
				Log.i(tag, "getSkuDetails() - \"DETAILS_LIST\" return " + responseList.toString());

				if (responseList.size() == 0) return;

				for (String thisResponse : responseList) {
					try {
						JSONObject object = new JSONObject(thisResponse);

						String sku   = object.getString("productId");
						String title = object.getString("title");
						String price = object.getString("price");

						Log.i(tag, "getSkuDetails() - \"DETAILS_LIST\":\"productId\" return " + sku);
						Log.i(tag, "getSkuDetails() - \"DETAILS_LIST\":\"title\" return " + title);
						Log.i(tag, "getSkuDetails() - \"DETAILS_LIST\":\"price\" return " + price);

						if (!sku.equals(productID)) continue;

						Bundle buyIntentBundle = mService.getBuyIntent(3, getPackageName(), sku, "inapp", "bGoa+V7g/yqDXvKRqq+JTFn4uQZbPiQJo4pf9RzJ");

						Toast.makeText(context, "getBuyIntent() - success return Bundle", Toast.LENGTH_SHORT).show();
						Log.i(tag, "getBuyIntent() - success return Bundle");

						response = buyIntentBundle.getInt("RESPONSE_CODE");
						Toast.makeText(context, "getBuyIntent() - \"RESPONSE_CODE\" return " + String.valueOf(response), Toast.LENGTH_SHORT).show();
						Log.i(tag, "getBuyIntent() - \"RESPONSE_CODE\" return " + String.valueOf(response));

						if (response != 0) continue;

						PendingIntent pendingIntent = buyIntentBundle.getParcelable("BUY_INTENT");
						startIntentSenderForResult(pendingIntent.getIntentSender(), 1001, new Intent(), 0, 0, 0);
					} catch (JSONException e) {
						e.printStackTrace();
					} catch (RemoteException e) {
						e.printStackTrace();

						Toast.makeText(context, "getSkuDetails() - fail!", Toast.LENGTH_SHORT).show();
						Log.w(tag, "getBuyIntent() - fail!");
					} catch (SendIntentException e) {
						e.printStackTrace();
					}
				}
			}
		});

		btnConsume.setOnClickListener(new View.OnClickListener() {
			@Override
			public void onClick(View arg0) {
				if (!blnBind) return;
				if (mService == null) return;

				int response;
				try {
					response = mService.consumePurchase(3, getPackageName(), "inapp:com.ethanf.in_app_billing_ex:android.test.purchased");

					Toast.makeText(context, "consumePurchase() - success : return " + String.valueOf(response), Toast.LENGTH_SHORT).show();
					Log.i(tag, "consumePurchase() - success : return " + String.valueOf(response));
				} catch (RemoteException e) {
					e.printStackTrace();

					Toast.makeText(context, "consumePurchase() - fail!", Toast.LENGTH_SHORT).show();
					Log.w(tag, "consumePurchase() - fail!");
					return;
				}

				if (response != 0) return;

				// TODO: management comsume purchase
			}
		});
	}

	@Override
	protected void onActivityResult(int requestCode, int resultCode, Intent data) {
		if (requestCode == 1001) {
			if (resultCode != RESULT_OK) return;

			int responseCode = data.getIntExtra("RESPONSE_CODE", 1);
			Toast.makeText(context, "onActivityResult() - \"RESPONSE_CODE\" return " + String.valueOf(responseCode), Toast.LENGTH_SHORT).show();
			Log.i(tag, "onActivityResult() - \"RESPONSE_CODE\" return " + String.valueOf(responseCode));

			if (responseCode != 0) return;

			String purchaseData = data.getStringExtra("INAPP_PURCHASE_DATA");
			String dataSignature = data.getStringExtra("INAPP_DATA_SIGNATURE");

			Log.i(tag, "onActivityResult() - \"INAPP_PURCHASE_DATA\" return " + purchaseData.toString());
			Log.i(tag, "onActivityResult() - \"INAPP_DATA_SIGNATURE\" return " + dataSignature.toString());

			// TODO: management purchase result
		}
	}

	@Override
	protected void onDestroy() {
		// Unbind Service
		if (mService != null)
			unbindService(mServiceConn);

		super.onDestroy();
	}
}

Hi, Could you tell me which bottoms dou you use to restore the purchase of application?? Please.