The line reporting the NPE is implicitly unboxing the Boolean returned by your Map's get method to retrieve a primitive boolean value. If get returns null it would have the behavior you describe.
On Tue, Jun 22, 2010 at 4:23 PM, Indicator Veritatis <[email protected]>wrote: > Hi, Mariano > > True, this is a Java question, not an Android question. SO it doesn't > r-e-a-l-l-y belong here. But in the interest of speeding you on your > way, I will make a couple observations I hope you will find helpful. > > 1) no, the NPE does not imply that isMarkAllReadPossibleCache is the > null variable. Rather, it implies that in the course of trying to > execute the get method of isMarkAllReadPossibleCache, the DVM > encountered a null pointer. > > 2) the NPE occurred during the call to UpdateButtons(), which in turn > took place during the call to the above get() method. > > 3) to tell in any more detail where it came from, I would need the > rest of your stack trace, which you chose not to show. But now you > have a better idea how to narrow this down by yourself, without > exposing the code to us, I hope. > > On Jun 22, 2:59 am, Mariano Kamp <[email protected]> wrote: > > Hey guys. > > > > This is not an Android issue per-se, but I am puzzled about a Java issue > and > > want to pick your brains. > > > > I recently got a couple of bug reports with a NPE that I don't understand > > and can't reproduce myself. Here is an abbreviated representation of the > > offending class. I tried to stay as close to the actual code as possible. > > > > public class EntryManager { > > > > private static EntryManager instance; > > private Map<DBQuery, Boolean> isMarkAllReadPossibleCache; > > > > private EntryManager(Context ctx) { > > .. > > isMarkAllReadPossibleCache = new HashMap<DBQuery, Boolean>(); > > .. > > } > > > > public static synchronized EntryManager getInstance(final Context > context) > > { > > if (instance == null) > > instance = new EntryManager(context.getApplicationContext()); > > return instance; > > } > > > > void fireModelUpdated(final String atomId) { > > .. > > isMarkAllReadPossibleCache.clear(); > > .. > > } > > > > public boolean isMarkAllReadPossible(final DBQuery dbq) { > > if (!isMarkAllReadPossibleCache.containsKey(dbq)) > > isMarkAllReadPossibleCache.put(dbq, > > databaseHelper.isMarkAllReadPossible(dbq)); > > > > return isMarkAllReadPossibleCache.get(dbq); <!-- NPE is raised > here > > } > > .. > > > > } > > > > In the last line from above a NPE is thrown. So the instance variable > > isMarkAllReadPossibleCache must be null, right? But I don't see where > this > > could happen. It's initialized in the constructor and never set to null > > afterwards. > > > > For completeness here is a stack trace: > > > > java.lang.NullPointerException > > at com.newsrob.EntryManager.isMarkAllReadPossible(EntryManager.java:1529) > > at > > > com.newsrob.activities.AbstractNewsRobListActivity.shouldMarkAllReadButtonBeEnabled(AbstractNewsRobListActivity.java:327) > > at > > > com.newsrob.activities.AbstractNewsRobListActivity.updateButtons(AbstractNewsRobListActivity.java:236) > > at > > > com.newsrob.activities.AbstractNewsRobListActivity.access$2(AbstractNewsRobListActivity.java:215) > > <-- removed the private access modifier meanwhile > > at > > > com.newsrob.activities.AbstractNewsRobListActivity$13.run(AbstractNewsRobListActivity.java:626) > > at android.os.Handler.handleCallback(Handler.java:587) > > at android.os.Handler.dispatchMessage(Handler.java:92) > > at android.os.Looper.loop(Looper.java:123) > > at android.app.ActivityThread.main(ActivityThread.java:4203) > > at java.lang.reflect.Method.invokeNative(Native Method) > > at java.lang.reflect.Method.invoke(Method.java:521) > > at > > > com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:791) > > at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:549) > > at dalvik.system.NativeStart.main(Native Method) > > > > Any ideas? > > > > Cheers, > > Mariano > > -- > You received this message because you are subscribed to the Google > Groups "Android Developers" group. > To post to this group, send email to [email protected] > To unsubscribe from this group, send email to > [email protected]<android-developers%[email protected]> > For more options, visit this group at > http://groups.google.com/group/android-developers?hl=en > -- You received this message because you are subscribed to the Google Groups "Android Developers" group. To post to this group, send email to [email protected] To unsubscribe from this group, send email to [email protected] For more options, visit this group at http://groups.google.com/group/android-developers?hl=en
