Crash in ListView at AbsListView.obtainView for ListActivity

Question

Hello:

I'm watching content updates on a ListActivity using a ContentObserver as follows:

protected void onCreate(Bundle savedState) { super.onCreate(savedState);

ContentResolver cr = getContentResolver();

Cursor cursor = cr.query(TrackHeader.CONTENT_URI, sTrackListProjection, null, null, null);
startManagingCursor(cursor);

this.mAdapter = new TrackHeaderDataAdapter(this, R.layout.track_list_item, cursor, sTrackListProjection, null);
setListAdapter(mAdapter);

Handler handler = new Handler();
mTrackHeaderObserver = new ContentObserver(handler) {

 @Override public boolean deliverSelfNotifications() { 
   return false;
 }

 @Override
 public void onChange(boolean selfChange) {
super.onChange(selfChange);
ContentResolver cr = getContentResolver();
   mAdapter.changeCursor(cr.query(TrackHeader.CONTENT_URI, sTrackListProjection, null, null, null));
 }
   };

getContentResolver().registerContentObserver (TrackHeader.CONTENT_URI, true, mTrackHeaderObserver);

}

This content observer seems to be ok -- it gets called back on the UI thread but I am getting the following random crash pretty predictably on the underlying ListView:

02-21 14:06:00.440: ERROR/AndroidRuntime(739): java.lang.NullPointerException 02-21 14:06:00.440: ERROR/AndroidRuntime(739): at android.widget.AbsListView.obtainView(AbsListView.java:1276) 02-21 14:06:00.440: ERROR/AndroidRuntime(739): at android.widget.ListView.makeAndAddView(ListView.java:1668) 02-21 14:06:00.440: ERROR/AndroidRuntime(739): at android.widget.ListView.fillDown(ListView.java:637) 02-21 14:06:00.440: ERROR/AndroidRuntime(739): at android.widget.ListView.fillSpecific(ListView.java:1224) 02-21 14:06:00.440: ERROR/AndroidRuntime(739): at android.widget.ListView.layoutChildren(ListView.java:1499) 02-21 14:06:00.440: ERROR/AndroidRuntime(739): at android.widget.AbsListView.onLayout(AbsListView.java:1113) 02-21 14:06:00.440: ERROR/AndroidRuntime(739): at android.view.View.layout(View.java:6830) 02-21 14:06:00.440: ERROR/AndroidRuntime(739): at android.widget.FrameLayout.onLayout(FrameLayout.java:333) 02-21 14:06:00.440: ERROR/AndroidRuntime(739): at android.view.View.layout(View.java:6830) 02-21 14:06:00.440: ERROR/AndroidRuntime(739): at android.widget.FrameLayout.onLayout(FrameLayout.java:333) 02-21 14:06:00.440: ERROR/AndroidRuntime(739): at android.view.View.layout(View.java:6830) 02-21 14:06:00.440: ERROR/AndroidRuntime(739): at android.widget.FrameLayout.onLayout(FrameLayout.java:333) 02-21 14:06:00.440: ERROR/AndroidRuntime(739): at android.view.View.layout(View.java:6830) 02-21 14:06:00.440: ERROR/AndroidRuntime(739): at android.widget.LinearLayout.setChildFrame(LinearLayout.java:1119) 02-21 14:06:00.440: ERROR/AndroidRuntime(739): at android.widget.LinearLayout.layoutVertical(LinearLayout.java:998) 02-21 14:06:00.440: ERROR/AndroidRuntime(739): at android.widget.LinearLayout.onLayout(LinearLayout.java:918) 02-21 14:06:00.440: ERROR/AndroidRuntime(739): at android.view.View.layout(View.java:6830) 02-21 14:06:00.440: ERROR/AndroidRuntime(739): at android.widget.FrameLayout.onLayout(FrameLayout.java:333) 02-21 14:06:00.440: ERROR/AndroidRuntime(739): at android.view.View.layout(View.java:6830) 02-21 14:06:00.440: ERROR/AndroidRuntime(739): at android.widget.FrameLayout.onLayout(FrameLayout.java:333) 02-21 14:06:00.440: ERROR/AndroidRuntime(739): at android.view.View.layout(View.java:6830) 02-21 14:06:00.440: ERROR/AndroidRuntime(739): at android.widget.FrameLayout.onLayout(FrameLayout.java:333) 02-21 14:06:00.440: ERROR/AndroidRuntime(739): at android.view.View.layout(View.java:6830) 02-21 14:06:00.440: ERROR/AndroidRuntime(739): at android.view.ViewRoot.performTraversals(ViewRoot.java:996) 02-21 14:06:00.440: ERROR/AndroidRuntime(739): at android.view.ViewRoot.handleMessage(ViewRoot.java:1633) 02-21 14:06:00.440: ERROR/AndroidRuntime(739): at android.os.Handler.dispatchMessage(Handler.java:99) 02-21 14:06:00.440: ERROR/AndroidRuntime(739): at android.os.Looper.loop(Looper.java:123) 02-21 14:06:00.440: ERROR/AndroidRuntime(739): at android.app.ActivityThread.main(ActivityThread.java:4363) 02-21 14:06:00.440: ERROR/AndroidRuntime(739): at java.lang.reflect.Method.invokeNative(Native Method) 02-21 14:06:00.440: ERROR/AndroidRuntime(739): at java.lang.reflect.Method.invoke(Method.java:521) 02-21 14:06:00.440: ERROR/AndroidRuntime(739): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:860) 02-21 14:06:00.440: ERROR/AndroidRuntime(739): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:618) 02-21 14:06:00.440: ERROR/AndroidRuntime(739): at dalvik.system.NativeStart.main(Native Method) 02-21 14:09:56.159: ERROR/AndroidRuntime(749): ERROR: thread attach failed 02-21 14:09:59.480: ERROR/AndroidRuntime(760): ERROR: thread attach failed 02-21 14:12:19.449: ERROR/AndroidRuntime(778): ERROR: thread attach failed 02-21 14:12:22.779: ERROR/AndroidRuntime(789): ERROR: thread attach failed 02-21 14:12:26.479: ERROR/gralloc(51): [unregister] handle 0x3f13b8 still locked (state=40000001)

Anyone seen anything like this before -- been stumped on this one for a few days...

Tim

Answer 1

I have not used changeCursor(). And, since the query you used to create the Cursor is the same as the query you are using to "change" the cursor, I'd dump the changeCursor() call outright and just call requery() on the Cursor you have.

Answer 2

I had a similar stack trace and discovered that I was returning a null from my getView() method in certain cases.