从ArrayList中删除标记：java.util.ConcurrentModificationException

Question

I have a checkboxlist where the user can select some routes then a reponse is being getting from the server. I have method gotoLocation to upadte the location of the markers as well to add a new marker in the map when a new one is being inserted into the table on the serverside with the same route.

I tried it before with HashMap<Integer, Marker> as <id, marker> but I had problem to add a new marker of the new request to the map so I tried it with ArrayList<Integer, String> and it works but I am getting now the error below when I try to remove a marker from the map.

How can I fix it?

Error:

07-16 00:19:05.663: E/AndroidRuntime(29919): FATAL EXCEPTION: main
07-16 00:19:05.663: E/AndroidRuntime(29919): Process: com.bustracker, PID: 29919
07-16 00:19:05.663: E/AndroidRuntime(29919): java.util.ConcurrentModificationException
07-16 00:19:05.663: E/AndroidRuntime(29919):    at java.util.ArrayList$ArrayListIterator.next(ArrayList.java:573)
07-16 00:19:05.663: E/AndroidRuntime(29919):    at com.bustracker.Map.gotoLocation(Map.java:132)
07-16 00:19:05.663: E/AndroidRuntime(29919):    at com.bustracker.Map.onNewIntent(Map.java:314)
07-16 00:19:05.663: E/AndroidRuntime(29919):    at android.app.Instrumentation.callActivityOnNewIntent(Instrumentation.java:1224)
07-16 00:19:05.663: E/AndroidRuntime(29919):    at android.app.ActivityThread.deliverNewIntents(ActivityThread.java:2833)
07-16 00:19:05.663: E/AndroidRuntime(29919):    at android.app.ActivityThread.performNewIntents(ActivityThread.java:2846)
07-16 00:19:05.663: E/AndroidRuntime(29919):    at android.app.ActivityThread.handleNewIntent(ActivityThread.java:2855)
07-16 00:19:05.663: E/AndroidRuntime(29919):    at android.app.ActivityThread.access$1700(ActivityThread.java:177)
07-16 00:19:05.663: E/AndroidRuntime(29919):    at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1520)
07-16 00:19:05.663: E/AndroidRuntime(29919):    at android.os.Handler.dispatchMessage(Handler.java:102)
07-16 00:19:05.663: E/AndroidRuntime(29919):    at android.os.Looper.loop(Looper.java:145)
07-16 00:19:05.663: E/AndroidRuntime(29919):    at android.app.ActivityThread.main(ActivityThread.java:5944)
07-16 00:19:05.663: E/AndroidRuntime(29919):    at java.lang.reflect.Method.invoke(Native Method)
07-16 00:19:05.663: E/AndroidRuntime(29919):    at java.lang.reflect.Method.invoke(Method.java:372)
07-16 00:19:05.663: E/AndroidRuntime(29919):    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1389)
07-16 00:19:05.663: E/AndroidRuntime(29919):    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1184)

Code:

    private void gotoLocation(int id, double lat, double lng,
            String route_direct) {
         ......
        // Update the location.
        for(Iterator<MapItem> it = mapItemList.iterator(); it.hasNext();){
            //Line 132.
            MapItem item1 = it.next();

            if(item1.getId() == id){
                marker = item1.getMarker();
                marker.remove();
                //int index = mapItemList.indexOf(item1);
                it.remove();
                ll = new LatLng(lat, lng);
                MarkerOptions markerOpt = new MarkerOptions().title(
                        route_direct).position(ll);
                marker = map.addMarker(markerOpt);
                 map.moveCamera(CameraUpdateFactory.newLatLngZoom(ll, 11));
                MapItem mapItem = new MapItem(id, marker);
                mapItemList.add(mapItem);

            }

        }
}

Answer 1

The exception is caused by mapItemList.add(mapItem); . Every modification to the collection, while you are iterating over it, will cause this exception. From the documentation

For example, if a thread modifies a collection directly while it is iterating over the collection with a fail-fast iterator, the iterator will throw this exception.

To fix you can use either use the ListIterator instead of the Iterator (to retrieve it use listIterator() ), and use iterator.add(mapItem); or you can use a temporary ArrayList where you will add the items you create while you are looping, and use addAll to add the whole content to the your mapItemList after the loop ends