-keep class com.android.vending.billing.**

E/AndroidRuntime: FATAL EXCEPTION: Thread-455
java.lang.NullPointerException
    at com.xx.xxxx.util.IabHelper.startSetup(Unknown Source)
    at com.xx.xxxx.util.IabHelper$2.run(Unknown Source)
    at java.lang.Thread.run(Thread.java:856)

-keep class com.android.vending.billing.**

-keep class com.xx.xxxx.util.IabHelper.**

mContext.getPackageManager()
                .queryIntentServices(serviceIntent, 0);

List<ResolveInfo> queryIntentServices = mContext.getPackageManager()
            .queryIntentServices(serviceIntent, 0);
    if (queryIntentServices != null && !queryIntentServices.isEmpty()) {
        // service available to handle that Intent
        mContext.bindService(serviceIntent, mServiceConn,
                Context.BIND_AUTO_CREATE);
    }else ...

-keep class com.android.vending.** { *; }