Android: NullPointerException using MapView

Android: NullPointerException when scrolling through a MapView w/ ItemizedOverlay

November 13th, 2010 | Posted by Jay in Computing

When I implemented a MapView with an ItemizedOverlay (the implementation steps are described in the Android developer documentation), I encountered a flaw in the API, or at least in the corresponding documentation. If you add an ItemizedOverlay to your MapView, but do not add any OverlayItems (which may be the default for your application, with OverlayItems being added during runtime), scrolling through the MapView causes the following NullPointerException:

ERROR/AndroidRuntime(232): java.lang.NullPointerException
  at com.google.android.maps.ItemizedOverlay.getItemsAtLocation(ItemizedOverlay.java:617)
  at com.google.android.maps.ItemizedOverlay.getItemAtLocation(ItemizedOverlay.java:586)
  at com.google.android.maps.ItemizedOverlay.handleMotionEvent(ItemizedOverlay.java:498)
  at com.google.android.maps.ItemizedOverlay.onTouchEvent(ItemizedOverlay.java:572)
  at com.google.android.maps.OverlayBundle.onTouchEvent(OverlayBundle.java:63)
  at com.google.android.maps.MapView.onTouchEvent(MapView.java:625)
  at android.view.View.dispatchTouchEvent(View.java:3709)
  at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:852)
  at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:822)
  at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:822)
  at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:822)
  at com.android.internal.policy.impl.PhoneWindow$DecorView.superDispatchTouchEvent(PhoneWindow.java:1659)
  at com.android.internal.policy.impl.PhoneWindow.superDispatchTouchEvent(PhoneWindow.java:1107)
  at android.app.Activity.dispatchTouchEvent(Activity.java:2061)
  at com.android.internal.policy.impl.PhoneWindow$DecorView.dispatchTouchEvent(PhoneWindow.java:1643)
  at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:822)
  at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:822)
  at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:822)
  at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:822)
  at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:822)
  at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:822)
  at com.android.internal.policy.impl.PhoneWindow$DecorView.superDispatchTouchEvent(PhoneWindow.java:1659)
  at com.android.internal.policy.impl.PhoneWindow.superDispatchTouchEvent(PhoneWindow.java:1107)
  at android.app.Activity.dispatchTouchEvent(Activity.java:2061)
  at com.android.internal.policy.impl.PhoneWindow$DecorView.dispatchTouchEvent(PhoneWindow.java:1643)
  at android.view.ViewRoot.handleMessage(ViewRoot.java:1691)
  at android.os.Handler.dispatchMessage(Handler.java:99)
  at android.os.Looper.loop(Looper.java:123)
  at android.app.ActivityThread.main(ActivityThread.java:4363)
  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:860)
  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:618)
  at dalvik.system.NativeStart.main(Native Method)

After long hours of debugging, I was able to find help in the Android Bug Tracking system. An easy workaround for this problem (which should really be addressed in the API and/or the corresponding documentation) is to add a call to the “populate()” function in the constructor of the class that extends ItemizedOverlay. Then, your subclass constructor should look like this:

super(boundCenterBottom(defaultMarker));
populate();

This solves the problem and scrolling, even without any OverlayItems, works like a charm.

Android, Java

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7 Responses

Thomas says:
Saturday, 11th December 2010 at 20:54
Just want to say Thank You to you, because you have resolve my probleme in few seconds only.
Thanks hundred !
Thoma.
Brandon says:
Tuesday, 21st December 2010 at 05:44
I ran into this problem too, solved the same way. Thanks for posting.
0x1B says:
Tuesday, 4th January 2011 at 21:47
I’ve been trying to hunt this down…. I will give this a try.
Thank you!
Reid says:
Monday, 31st January 2011 at 20:49
Seriously man.. you SAVED ME A TON ON THISS!!!!! THANKS!
Stephan says:
Tuesday, 8th March 2011 at 04:20
Thank you for this post!
elKaetzo says:
Thursday, 10th March 2011 at 04:46
You saved my evening! Thanks a million!
KP says:
Saturday, 3rd December 2011 at 14:24
Thank you! was already wondering why this happens…
Fixed now!

Android: NullPointerException when scrolling through a MapView w/ ItemizedOverlay

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