I have a relatively simple MapActivity that I'm trying to make display
a list of "camps" within a given map region. I've created a custom
subclass of OverlayItem called CampOverlayItem, a custom
ItemizedOverlay called CampsOverlay that returns CampOverlayItems, and
of course a MapActivity subclass that populates the map.
I'm pulling the overlay data from a database using an AsyncTask as
created in my activity. The AsyncTask is triggered from a
ViewTreeObserver.OnGlobalLayoutListener attached to the MapView.
In the onPostExecute method of the AsyncTask, I create a new instance
of my CampsOverlay class and pass it a list of the camps returned from
the database (which are fetched in doInBackground). I then call:
mapView.getOverlays().add(newOverlay);
where newOverlay is the CampsOverlay I just created. All of this code
runs without error, but when the Map tries to draw itself, I get a
NullPointerException with the following stack trace:
java.lang.NullPointerException
at
com.google.android.maps.ItemizedOverlay.getIndexToDraw(ItemizedOverlay.java:
211)
at
com.google.android.maps.ItemizedOverlay.draw(ItemizedOverlay.java:240)
at com.google.android.maps.Overlay.draw(Overlay.java:179)
at com.google.android.maps.OverlayBundle.draw(OverlayBundle.java:
42)
at com.google.android.maps.MapView.onDraw(MapView.java:476)
at android.view.View.draw(View.java:6274)
at android.view.ViewGroup.drawChild(ViewGroup.java:1526)
at android.view.ViewGroup.dispatchDraw(ViewGroup.java:1256)
at android.view.ViewGroup.drawChild(ViewGroup.java:1524)
at android.view.ViewGroup.dispatchDraw(ViewGroup.java:1256)
at android.view.View.draw(View.java:6277)
at android.widget.FrameLayout.draw(FrameLayout.java:352)
at android.view.ViewGroup.drawChild(ViewGroup.java:1526)
at android.view.ViewGroup.dispatchDraw(ViewGroup.java:1256)
at android.view.ViewGroup.drawChild(ViewGroup.java:1524)
at android.view.ViewGroup.dispatchDraw(ViewGroup.java:1256)
at android.view.ViewGroup.drawChild(ViewGroup.java:1524)
at android.view.ViewGroup.dispatchDraw(ViewGroup.java:1256)
at android.view.ViewGroup.drawChild(ViewGroup.java:1524)
at android.view.ViewGroup.dispatchDraw(ViewGroup.java:1256)
at android.view.ViewGroup.drawChild(ViewGroup.java:1524)
at android.view.ViewGroup.dispatchDraw(ViewGroup.java:1256)
at android.view.View.draw(View.java:6277)
at android.widget.FrameLayout.draw(FrameLayout.java:352)
at android.view.ViewGroup.drawChild(ViewGroup.java:1526)
at android.view.ViewGroup.dispatchDraw(ViewGroup.java:1256)
at android.view.View.draw(View.java:6277)
at android.widget.FrameLayout.draw(FrameLayout.java:352)
at com.android.internal.policy.impl.PhoneWindow
$DecorView.draw(PhoneWindow.java:1883)
at android.view.ViewRoot.draw(ViewRoot.java:1332)
at android.view.ViewRoot.performTraversals(ViewRoot.java:1097)
at android.view.ViewRoot.handleMessage(ViewRoot.java:1613)
at android.os.Handler.dispatchMessage(Handler.java:99)
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)
Because it seems particularly relevant, here is the code for my
ItemizedOverlay subclass:
public class CampsOverlay extends ItemizedOverlay<CampOverlayItem> {
private ArrayList<Camp> camps = null;
public CampsOverlay(Drawable defaultMarker, ArrayList<Camp> theCamps)
{
super(defaultMarker);
this.camps = theCamps;
}
@Override
protected CampOverlayItem createItem(int i) {
Camp camp = camps.get(i);
CampOverlayItem item = new CampOverlayItem(camp);
return item;
}
@Override
protected boolean onTap(int index) {
// TODO Auto-generated method stub
return super.onTap(index);
}
@Override
public int size() {
return camps.size();
}
}
Does anyone have any idea what could be happening here? I've attempted
to verify that everything I have control over is non-null. I can
provide more code if necessary.
