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Editorial Team
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Asked: 2026-05-27T14:25:21+00:00

I am creating a map application that receives a list of coords from a

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I am creating a map application that receives a list of coords from a JSON array. I @Override dispatchTouchEvent to find the coords from the map and then execute an ASYNCTask to get the new points.

It loads the points but after scrolling around it force closes. What would be ideal is to clear the current points on the map and reload new points from a new location after the touch event.

Here is my code so far:

@Override
public boolean dispatchTouchEvent(MotionEvent ev) {
    int actionType = ev.getAction();
    switch (actionType) {
    case MotionEvent.ACTION_UP:
        Projection proj = mapView.getProjection();
        GeoPoint loc = proj.fromPixels((int) ev.getX(), (int) ev.getY());
        String lng = Double.toString(loc.getLongitudeE6() / 1e6);
        String lat = Double.toString(loc.getLatitudeE6() / 1e6);

        new mapStations().execute();

        Toast.makeText(getApplicationContext(),
                "Lat: " + lat + " Lng: " + lng, Toast.LENGTH_SHORT).show();
    }

    return super.dispatchTouchEvent(ev);
}

private class mapStations extends AsyncTask<Void, Void, Void> {

    @Override
    protected Void doInBackground(Void... arg0) {
        try {
            JSONObject obj = new JSONObject(API.nearByStations(lat, lng, 0));
            JSONArray stations = obj.getJSONArray("stations");
            for (int j = 0; j < stations.length(); j++) {
                JSONObject jsonObject = stations.getJSONObject(j);
                add(jsonObject.getDouble("lat"), jsonObject.getDouble("lng"));

            }

        } catch (JSONException e) {
            e.printStackTrace();
        }

        return null;
    }
}

public void add(double lat, double lng) {

    mapOverlays = mapView.getOverlays();
    drawable = this.getResources().getDrawable(R.drawable.androidmarker);
    itemizedOverlay = new MapsOverlay(drawable);

    GeoPoint point = new GeoPoint((int) (lat * 1e6), (int) (lng * 1e6));
    OverlayItem overlayitem = new OverlayItem(point, "", "");

    itemizedOverlay.addOverlay(overlayitem);
    mapOverlays.add(itemizedOverlay);
}

LogCat:

12-18 22:52:01.076: E/AndroidRuntime(25072): FATAL EXCEPTION: main
12-18 22:52:01.076: E/AndroidRuntime(25072): java.util.ConcurrentModificationException
12-18 22:52:01.076: E/AndroidRuntime(25072):    at java.util.ArrayList$ArrayListIterator.next(ArrayList.java:576)
12-18 22:52:01.076: E/AndroidRuntime(25072):    at com.google.android.maps.OverlayBundle.draw(OverlayBundle.java:41)
12-18 22:52:01.076: E/AndroidRuntime(25072):    at com.google.android.maps.MapView.onDraw(MapView.java:530)
12-18 22:52:01.076: E/AndroidRuntime(25072):    at android.view.View.draw(View.java:6880)
12-18 22:52:01.076: E/AndroidRuntime(25072):    at android.view.ViewGroup.drawChild(ViewGroup.java:1646)
12-18 22:52:01.076: E/AndroidRuntime(25072):    at android.view.ViewGroup.dispatchDraw(ViewGroup.java:1373)
12-18 22:52:01.076: E/AndroidRuntime(25072):    at android.view.ViewGroup.drawChild(ViewGroup.java:1644)
12-18 22:52:01.076: E/AndroidRuntime(25072):    at android.view.ViewGroup.dispatchDraw(ViewGroup.java:1373)
12-18 22:52:01.076: E/AndroidRuntime(25072):    at android.view.View.draw(View.java:6883)
12-18 22:52:01.076: E/AndroidRuntime(25072):    at android.widget.FrameLayout.draw(FrameLayout.java:357)
12-18 22:52:01.076: E/AndroidRuntime(25072):    at android.view.ViewGroup.drawChild(ViewGroup.java:1646)
12-18 22:52:01.076: E/AndroidRuntime(25072):    at android.view.ViewGroup.dispatchDraw(ViewGroup.java:1373)
12-18 22:52:01.076: E/AndroidRuntime(25072):    at android.view.ViewGroup.drawChild(ViewGroup.java:1644)
12-18 22:52:01.076: E/AndroidRuntime(25072):    at android.view.ViewGroup.dispatchDraw(ViewGroup.java:1373)
12-18 22:52:01.076: E/AndroidRuntime(25072):    at android.view.ViewGroup.drawChild(ViewGroup.java:1644)
12-18 22:52:01.076: E/AndroidRuntime(25072):    at android.view.ViewGroup.dispatchDraw(ViewGroup.java:1373)
12-18 22:52:01.076: E/AndroidRuntime(25072):    at android.view.ViewGroup.drawChild(ViewGroup.java:1644)
12-18 22:52:01.076: E/AndroidRuntime(25072):    at android.view.ViewGroup.dispatchDraw(ViewGroup.java:1373)
12-18 22:52:01.076: E/AndroidRuntime(25072):    at android.view.ViewGroup.drawChild(ViewGroup.java:1644)
12-18 22:52:01.076: E/AndroidRuntime(25072):    at android.view.ViewGroup.dispatchDraw(ViewGroup.java:1373)
12-18 22:52:01.076: E/AndroidRuntime(25072):    at android.view.View.draw(View.java:6883)
12-18 22:52:01.076: E/AndroidRuntime(25072):    at android.widget.FrameLayout.draw(FrameLayout.java:357)
12-18 22:52:01.076: E/AndroidRuntime(25072):    at android.view.ViewGroup.drawChild(ViewGroup.java:1646)
12-18 22:52:01.076: E/AndroidRuntime(25072):    at android.view.ViewGroup.dispatchDraw(ViewGroup.java:1373)
12-18 22:52:01.076: E/AndroidRuntime(25072):    at android.view.ViewGroup.drawChild(ViewGroup.java:1644)
12-18 22:52:01.076: E/AndroidRuntime(25072):    at android.view.ViewGroup.dispatchDraw(ViewGroup.java:1373)
12-18 22:52:01.076: E/AndroidRuntime(25072):    at android.view.View.draw(View.java:6883)
12-18 22:52:01.076: E/AndroidRuntime(25072):    at android.widget.FrameLayout.draw(FrameLayout.java:357)
12-18 22:52:01.076: E/AndroidRuntime(25072):    at com.android.internal.policy.impl.PhoneWindow$DecorView.draw(PhoneWindow.java:2106)
12-18 22:52:01.076: E/AndroidRuntime(25072):    at android.view.ViewRoot.draw(ViewRoot.java:1562)
12-18 22:52:01.076: E/AndroidRuntime(25072):    at android.view.ViewRoot.performTraversals(ViewRoot.java:1298)
12-18 22:52:01.076: E/AndroidRuntime(25072):    at android.view.ViewRoot.handleMessage(ViewRoot.java:1911)
12-18 22:52:01.076: E/AndroidRuntime(25072):    at android.os.Handler.dispatchMessage(Handler.java:99)
12-18 22:52:01.076: E/AndroidRuntime(25072):    at android.os.Looper.loop(Looper.java:130)
12-18 22:52:01.076: E/AndroidRuntime(25072):    at android.app.ActivityThread.main(ActivityThread.java:3821)
12-18 22:52:01.076: E/AndroidRuntime(25072):    at java.lang.reflect.Method.invokeNative(Native Method)
12-18 22:52:01.076: E/AndroidRuntime(25072):    at java.lang.reflect.Method.invoke(Method.java:507)
12-18 22:52:01.076: E/AndroidRuntime(25072):    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:839)
12-18 22:52:01.076: E/AndroidRuntime(25072):    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:597)
12-18 22:52:01.076: E/AndroidRuntime(25072):    at dalvik.system.NativeStart.main(Native Method)

In a later note I would like to have different icons for each point and a tap event to bring up more details about that point the user taps. I spent about six hours on this last night and could not figure it out. The logcat doesn’t really tell much.

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1 Answer

  1. Editorial Team

    You should add the items in the UI thread, not in background.

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