How do you understand the cause of exception having stacktrace?

Question

We have written an Android application which sends stack traces to our server, if any occur. Sometimes we get weird stack traces that seem not to be an exception from our application. For example:

java.lang.NullPointerException
at android.widget.FastScroller.scrollTo1(FastScroller.java:306)
at android.widget.FastScroller.onTouchEvent(FastScroller.java:507)
at android.widget.AbsListView.onTouchEvent(AbsListView.java:1894)
at android.widget.ListView.onTouchEvent(ListView.java:3083)
at android.view.View.dispatchTouchEvent(View.java:3386)
at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:831)
at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:863)
at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:863)
at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:863)
at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:863)
at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:863)
at com.android.internal.policy.impl.PhoneWindow$DecorView.superDispatchTouchEvent(PhoneWindow.java:1710)
at com.android.internal.policy.impl.PhoneWindow.superDispatchTouchEvent(PhoneWindow.java:1197)
at android.app.Activity.dispatchTouchEvent(Activity.java:1993)
at com.android.internal.policy.impl.PhoneWindow$DecorView.dispatchTouchEvent(PhoneWindow.java:1694)
at android.view.ViewRoot.handleMessage(ViewRoot.java:1525)
at android.os.Handler.dispatchMessage(Handler.java:99)
at android.os.Looper.loop(Looper.java:123)
at android.app.ActivityThread.main(ActivityThread.java:3952)
at java.lang.reflect.Method.invokeNative(Native Method)
at java.lang.reflect.Method.invoke(Method.java:521)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:782)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:540)
at dalvik.system.NativeStart.main(Native Method)

There is no mention of our own classes, only Android's standard classes. It's obvious that this exception takes place when scrolling of item list (ListView) occurs, but I can't even uderstand how I can fix this bug. I can't reproduce this bug. What do you usually do when you encounter the same problem? Any ideas?

Answer 1

Tehere is something wrong with fast scrolling of some ListView using a thumb. If you set fast scrolling enabled of your ListView make sure the adapter class implements SectionIndexer.