[android-developers] itemizedOverlay, onTap

[rochi]

hello, I'm having problems with this code:

http://developer.android.com/resources/tutorials/views/hello-mapview.html


In main.xml I have:

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/
android"
    android:id="@+id/mainlayout"
    android:orientation="vertical"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent" >

  <com.google.android.maps.MapView
        android:id="@+id/mapview"
        android:layout_width="fill_parent"
        android:layout_height="fill_parent"
        android:clickable="true"
        android:apiKey="myKey"
    />


</RelativeLayout>

In the AndroidManifest.xml

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android";
      package="maps.rochi"
      android:versionCode="1"
      android:versionName="1.0">
    <uses-sdk android:minSdkVersion="13" />

    <uses-permission android:name="android.permission.INTERNET" />


    <application android:icon="@drawable/icon" android:label="@string/
app_name">

        <uses-library android:name="com.google.android.maps" />


        <activity android:name=".MapsActivity"
                  android:label="@string/app_name">
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />
                <category
android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>

    </application>

</manifest>

In mapsActivity.java:

public class MapsActivity extends MapActivity {

        LinearLayout linearLayout;
        MapView mapView;
        MapController mapController;

        List<Overlay> mapOverlays;
        Drawable drawable;
        helloItemizedOverlay itemizedOverlay;


    protected boolean isRouteDisplayed() {
        return false;
    }

    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);

        mapView = (MapView) findViewById(R.id.mapview);
        mapView.setBuiltInZoomControls(true);

        mapController = mapView.getController();

        mapOverlays = mapView.getOverlays();
        drawable =
this.getResources().getDrawable(R.drawable.bikeicon);
        itemizedOverlay = new helloItemizedOverlay(drawable);

        GeoPoint point = new GeoPoint(19240000,-99120000);
        OverlayItem overlayitem = new OverlayItem(point, "Hola,
Mundo!", "I'm in Mexico City!");


        itemizedOverlay.addOverlay(overlayitem);

        mapOverlays.add(itemizedOverlay);


    }
}

And helloItemizedOverlay:

public class helloItemizedOverlay extends ItemizedOverlay {

    Context mContext = null;
    private ArrayList<OverlayItem> mOverlays = new
ArrayList<OverlayItem>();


    public helloItemizedOverlay(Drawable marker) {
        super(boundCenterBottom(marker));

    }

        public void addOverlay(OverlayItem overlay) {
            mOverlays.add(overlay);
            populate();
        }

        @Override
        protected OverlayItem createItem(int i) {
          return mOverlays.get(i);
        }

        @Override
        public int size() {
                // TODO Auto-generated method stub
                return mOverlays.size();
        }

    public helloItemizedOverlay(Drawable defaultMarker, Context
context) {
        super(defaultMarker);
        mContext = context;
    }

        @Override
        protected boolean onTap(int index){
                  OverlayItem item = mOverlays.get(index);
                  try{
                          AlertDialog.Builder dialog = new 
AlertDialog.Builder(mContext);
                          dialog.setTitle(item.getTitle());
                          dialog.setMessage(item.getSnippet());
                          dialog.show();
                  } catch (Exception e){
                          e.printStackTrace();
                  }

                  return true;
        }

}


When I click in some icon, I found a nullPointerException in  this
line AlertDialog.Builder dialog = new AlertDialog.Builder(mContext);

what's my mistake???

Thank you so much!

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