title: NullPointerException InAppBilling.IabHelper.launchPurchaseFlow(IabHelper.java:356)
body: <p>I have implemented In-App Billing in my project  but some times it give the following NullPointerException IabHelper.launchPurchaseFlow() method. currently i m using reserved ID's for testing and apk is not signed.</p>
  
  <pre><code>02-01 01:53:56.097: E/AndroidRuntime(9314): java.lang.NullPointerException
  02-01 01:53:56.097: E/AndroidRuntime(9314):     at com.example.app.InAppBilling.IabHelper.launchPurchaseFlow(IabHelper.java:356)
  02-01 01:53:56.097: E/AndroidRuntime(9314):     at com.example.app.InAppBilling.IabHelper.launchPurchaseFlow(IabHelper.java:307)
  02-01 01:53:56.097: E/AndroidRuntime(9314):     at com.example.app.MYTabActivity$4.onClick(MYTabActivity.java:418)
  02-01 01:53:56.097: E/AndroidRuntime(9314):     at com.android.internal.app.AlertController$ButtonHandler.handleMessage
  .
  </code></pre>
  
  <p>.
  .</p>