I've received my first Exception. Now what do I do?

I'm new to all this crazy Android/Java programming stuff. I have an app that (somehow) I managed开发者_JS百科 to figure out how to add in-app billing items to. I'm pretty sure the error is related to in-app billing, but I'm not able to reproduce the problem on any of my devices.

    NullPointerException
    in ComponentName.<init>()

    java.lang.RuntimeException: Unable to destroy activity {ca.ajwest.BeerConverter/ca.ajwest.BeerConverter.BeerConverter}: java.lang.NullPointerException
    at android.app.ActivityThread.performDestroyActivity(ActivityThread.java:3035)
    at android.app.ActivityThread.handleDestroyActivity(ActivityThread.java:3100)
    at android.app.ActivityThread.handleRelaunchActivity(ActivityThread.java:3216)
    at android.app.ActivityThread.access$1600(ActivityThread.java:132)
    at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1037)
    at android.os.Handler.dispatchMessage(Handler.java:99)
    at android.os.Looper.loop(Looper.java:143)
    at android.app.ActivityThread.main(ActivityThread.java:4196)
    at java.lang.reflect.Method.invokeNative(Native Method)
    at java.lang.reflect.Method.invoke(Method.java:507)
    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:839)
    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:597)
    at dalvik.system.NativeStart.main(Native Method)
    Caused by: java.lang.NullPointerException
    at android.content.ComponentName.<init>(ComponentName.java:75)
    at android.content.Intent.<init>(Intent.java:2893)
    at ca.ajwest.BeerConverter.BillingHelper.stopService(BillingHelper.java:270)
    at ca.ajwest.BeerConverter.BeerConverter.onDestroy(BeerConverter.java:615)
    at android.app.ActivityThread.performDestroyActivity(ActivityThread.java:3017)
    ... 12 more

Could somebody please direct me to some resources where I can learn more about this output or something? Does anybody have any similar experiences?

Here's the source if that helps at all.

Thanks for your help.

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You should look your line 270 in BillingHelper.java and line 615 in BillingConverter. In error log, you should look for mainly two things; first, a line number which is related with your application names, second; name of the exception.

You see that

Caused by: java.lang.NullPointerException
at android.content.ComponentName.<init>(ComponentName.java:75)
at android.content.Intent.<init>(Intent.java:2893)
at ca.ajwest.BeerConverter.BillingHelper.stopService(BillingHelper.java:270)
at ca.ajwest.BeerConverter.BeerConverter.onDestroy(BeerConverter.java:615)

says, there is a null pointer exception in one of your classes. Line numbers are also noted to check. There should be a variable, which isn't initialized or already destroyed.

I hope that helps.

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You got an "Exception", while executing your code. Basically, something went wrong. Oracle's definition is "An exception is an event, which occurs during the execution of a program, that disrupts the normal flow of the program's instructions."

Take a look here to learn more

In particular you got the NPE, NullPointerException

From Javadoc:

Thrown when an application attempts to use null in a case where an object is required. These include:

• Calling the instance method of a null object.
• Accessing or modifying the field of a null object.
• Taking the length of null as if it were an array.
• Accessing or modifying the slots of null as if it were an array.
• Throwing null as if it were a Throwable value.

In other words, your program expected some object and got nothing in return.