我使用这些代码进行付款并检查服务器上的购买证明：
http://www.aghsatiha.com/pardakht.txt
但它不起作用，我有这个错误：
05-21 23:04:06.277: E/AndroidRuntime(4204): java.lang.IllegalStateException: Can't start async operation (launchPurchaseFlow) because another async operation(refresh inventory) is in progress.
05-21 23:04:06.277: E/AndroidRuntime(4204): at com.util.IabHelper.flagStartAsync(IabHelper.java:8 22)
05-21 23:04:06.277: E/AndroidRuntime(4204): at com.util.IabHelper.launchPurchaseFlow(IabHelper.ja va:373)
05-21 23:04:06.277: E/AndroidRuntime(4204): at com.util.IabHelper.launchPurchaseFlow(IabHelper.ja va:338)
05-21 23:04:06.277: E/AndroidRuntime(4204): at com.deser.srp.Kharid$4.onClick(Kharid.java:77)
05-21 23:04:06.277: E/AndroidRuntime(4204): at android.view.View.performClick(View.java:4463)
05-21 23:04:06.277: E/AndroidRuntime(4204): at android.view.View$PerformClick.run(View.java:18770 )
05-21 23:04:06.277: E/AndroidRuntime(4204): at android.os.Handler.handleCallback(Handler.java:808 )
05-21 23:04:06.277: E/AndroidRuntime(4204): at android.os.Handler.dispatchMessage(Handler.java:10 3)
05-21 23:04:06.277: E/AndroidRuntime(4204): at android.os.Looper.loop(Looper.java:193)
05-21 23:04:06.277: E/AndroidRuntime(4204): at android.app.ActivityThread.main(ActivityThread.jav a:5333)
05-21 23:04:06.277: E/AndroidRuntime(4204): at java.lang.reflect.Method.invokeNative(Native Method)
05-21 23:04:06.277: E/AndroidRuntime(4204): at java.lang.reflect.Method.invoke(Method.java:515)
05-21 23:04:06.277: E/AndroidRuntime(4204): at com.android.internal.os.ZygoteInit$MethodAndArgsCa ller.run(ZygoteInit.java:829)
05-21 23:04:06.277: E/AndroidRuntime(4204): at com.android.internal.os.ZygoteInit.main(ZygoteInit .java:645)
05-21 23:04:06.277: E/AndroidRuntime(4204): at dalvik.system.NativeStart.main(Native Method)
任何人都可以帮助我吗？